Tadalafil: how it works, uses, evidence, and risks

A clear lens and blue woven canopy hover above a yellow and ivory capsule.

Tadalafil is a prescription medicine used for erectile dysfunction, urinary symptoms associated with an enlarged prostate, and a particular form of high blood pressure in the lungs. It stays in the body long enough to allow either occasional or daily treatment, depending on the condition. The expected benefits, doses, and monitoring differ substantially between those uses.

The approval information in this article refers to the US Food and Drug Administration. Compounded tadalafil products also require a prescription, but they should not be assumed equivalent to approved Cialis or Adcirca tablets. Choosing a product and treatment schedule requires an assessment of the condition, other medicines, and individual risks.

Tadalafil is best known as the “weekend pill.” Its effects also extend to blood vessels elsewhere in the body, the lower urinary tract, and the pulmonary circulation. For erectile dysfunction, an approved low-dose daily schedule offers an alternative to taking a pill around the time of sex. That distinction concerns this indication; it does not mean other PDE5 inhibitors are never used regularly for other conditions. Background on daily treatment

Cialis and Adcirca are brand-name tadalafil products; approved generic tablets are also available. Pharmacies may prepare compounded formulations for an individual prescription. Understanding the differences starts with the mechanism, the clinical evidence for each indication, and the assessment that makes prescribing appropriate.

The key points

The FDA approved tadalafil as Cialis for erectile dysfunction in 2003 and for symptoms of benign prostatic hyperplasia in 2011. Approval for pulmonary arterial hypertension followed in 2009 under the name Adcirca. Compounded products may be prescribed and prepared through appropriately licensed professionals and pharmacies.
Approved manufactured medicines are available. Compounded formulations do not have their own FDA approval.
Tadalafil requires a prescription. Restrictions on one provider’s service or geographic availability do not describe the availability of the medicine as a whole.
DailyMed provides the older Cialis label and the current Cialis prescribing information. The older 2009 label predates the BPH indication.
Tadalafil inhibits PDE5. This slows the breakdown of the signaling molecule cGMP and prolongs nitric-oxide-mediated relaxation of smooth muscle.
Clinical trials show improvements in erectile function, urinary symptoms associated with prostate enlargement, and exercise capacity in pulmonary arterial hypertension. The doses and populations differ by indication.

What is tadalafil?

Tadalafil belongs to the phosphodiesterase type 5 inhibitor family, usually shortened to PDE5 inhibitors. Other members include sildenafil, known as Viagra, and vardenafil, known as Levitra. One important difference is how long each medicine remains in the body. Tadalafil’s elimination half-life is about 17.5 hours, compared with roughly 4–5 hours for sildenafil and vardenafil. After one half-life, the concentration in the blood has fallen by approximately half. Tadalafil’s longer residence time supports its once-daily erectile dysfunction schedule. Pharmacokinetics, background on use

Compounded lozenges, sometimes called troches, dissolve under the tongue or against the cheek. Evidence about their absorption cannot simply be borrowed from every other formulation that dissolves in the mouth. One study compared an orodispersible film with a conventional tablet and found comparable drug exposure under fasting conditions. It did not study compounded troches. How reliably a particular lozenge delivers tadalafil therefore needs its own consideration when selecting the formulation and dose. Park and colleagues, 2018

A licensed pharmacy can prepare a compounded product without that product itself being FDA-approved. Its safety, effectiveness, and quality have not undergone the same product-specific approval process as an approved manufactured medicine. Compounded preparations can differ in dosage form, concentration, and inactive ingredients.

The clinical results discussed here concern tadalafil regimens studied in trials of manufactured products. They should not automatically be transferred to an individually compounded lozenge or another untested formulation. Approved generic tablets and compounded preparations are different regulatory categories.

How tadalafil works in the body

PDE5 inhibition and the cGMP pathway

Tadalafil selectively inhibits phosphodiesterase type 5. This enzyme breaks down cyclic guanosine monophosphate, or cGMP, inside smooth muscle cells. Sexual stimulation prompts nitric oxide release from nerves and the blood vessel lining. Nitric oxide activates guanylate cyclase, the enzyme that produces cGMP.

In the penis, cGMP relaxes smooth muscle in the erectile tissue, allowing more blood to enter. PDE5 helps end that signal by breaking down cGMP. By slowing this breakdown, tadalafil keeps the signal available for longer and supports the relaxation response.

The medicine amplifies an existing physiological response. It does not replace sexual stimulation or automatically produce an erection.

A 2021 overview by Pyrgidis and colleagues in Frontiers in Pharmacology included 23 systematic reviews covering 563 primary studies and 154,796 participants. Those totals describe the whole overview, largely concerned with erectile function. Its discussion of endothelial dysfunction drew on a much smaller included meta-analysis: 13 studies with 932 participants. That analysis did not establish a significant improvement in endothelial function and called for better primary studies. Animal findings had therefore not translated consistently to the human studies available at that time. This is a bounded negative finding, rather than proof that PDE5 inhibitors can never affect blood vessel function. Pyrgidis and colleagues, 2021

Effects on the endothelium and blood vessels

PDE5 is present in blood vessels outside the penis. By keeping cGMP available, tadalafil can influence vascular tone and function elsewhere in the body.

A meta-analysis by Zhang and colleagues, published on December 30, 2025, pooled 63 randomized controlled trials with 3,242 participants. Participants in these trials were randomly assigned to a treatment or comparison group. Compared with placebo, the analysis reported the following results for PDE5 inhibitors as a class:

Flow-mediated dilation increased by a mean 2.47 percentage points on a measure expressed as a percentage; 95% confidence interval, 1.24–3.71; p < 0.001.
Pulse wave velocity decreased by a reported mean 0.75; 95% confidence interval, −1.01 to −0.49; p < 0.001. The paper labels this unit cm/s. Because the scale needs clarification against the underlying trials, it should not be treated here as a verified clinical change of 0.75 cm/s or silently converted to m/s.
Systolic blood pressure decreased by a mean 2.80 mmHg; 95% confidence interval, −4.24 to −1.37; p < 0.001.

Flow-mediated dilation measures how well an artery widens as blood flow increases. Pulse wave velocity is used to assess arterial stiffness. A confidence interval conveys uncertainty around an estimate; a small p value does not by itself establish that a change is large or clinically important. The newer analysis used a broader evidence base and several vascular outcomes, so it is not a direct replication of the older endothelial-function analysis. Its positive findings also concerned PDE5 inhibitors collectively, not tadalafil alone. Zhang and colleagues

A smaller 2017 study by Özdabakoğlu and colleagues examined 30 men with erectile dysfunction but no known cardiovascular disease and 20 healthy controls. The men with erectile dysfunction had a mean age of 48.7 years. After a single tadalafil dose, systolic blood pressure fell (p = 0.001), as did pulse pressure, the difference between systolic and diastolic pressure (p = 0.018).

Aortic distensibility improved (p = 0.001), along with aortic strain (p = 0.003) and elasticity indices for large and small arteries (p = 0.02 and p = 0.003). The left ventricle’s diastolic function (its ability to relax and fill) also improved. These were short-term physiological measurements. Özdabakoğlu and colleagues, 2017

Such findings help explain interest in tadalafil beyond its approved indications. They do not establish that prescribing it to prevent cardiovascular disease improves long-term outcomes. That question requires clinical outcome studies, not just changes in vessel measurements.

Effects on the lower urinary tract and prostate

PDE5 is also found in smooth muscle in the prostate, bladder neck, and urethra. Inhibiting it may reduce muscle tone in those tissues. This is one proposed explanation for improvements in symptoms of benign prostatic hyperplasia, or BPH, and lower urinary tract symptoms, or LUTS.

Alpha-blockers such as tamsulosin act in the same general region through a different pathway, involving adrenergic receptors.

A 2020 meta-analysis by Guo and colleagues in Medical Science Monitor included seven randomized trials and 1,601 patients. It found no significant differences between tadalafil and tamsulosin in total International Prostate Symptom Score, or IPSS, or in its storage and voiding subscores. The IPSS is a questionnaire that captures the severity of urinary symptoms. Quality of life, maximum urinary flow rate (Qmax), and the amount of urine left after urination also did not differ significantly.

Tadalafil performed significantly better on the International Index of Erectile Function, or IIEF, a questionnaire covering sexual and erectile function. That difference may matter when urinary symptoms and erectile dysfunction occur together. Similar average results on some outcomes do not mean the two medicines are interchangeable for every patient. Guo and colleagues, 2020

Effects on blood vessels in the lungs

PDE5 is abundant in the smooth muscle of pulmonary arteries. In pulmonary arterial hypertension, or PAH, resistance in these vessels is elevated. That places extra strain on the right side of the heart and can reduce exercise capacity.

Inhibiting PDE5 helps the pulmonary vessels relax. This is the basis for tadalafil’s use as Adcirca in PAH.

The molecular pathway is the same in the systemic and pulmonary circulations. What differs between Cialis for erectile dysfunction and Adcirca for PAH is chiefly the dose, patient population, and evidence supporting the indication. The PAH regimen is not an erectile dysfunction regimen at a higher dose.

Pharmacokinetics and the daily schedule

Forgue and colleagues studied tadalafil pharmacokinetics in 237 healthy participants receiving single doses of 2.5–20 mg. Their 2006 report in the British Journal of Clinical Pharmacology gave a half-life of 17.5 hours, with the 5th–95th percentile spanning 11.5–29.6 hours. That range illustrates meaningful variation between individuals. Sildenafil and vardenafil are cleared more rapidly, with half-lives around 4–5 hours. Forgue and colleagues, 2006

With daily tadalafil, steady state is reached after roughly five days. At that point, repeated dosing and elimination produce a relatively consistent exposure pattern. This lets sexual activity be less closely tied to a particular dose. Food does not materially change tadalafil absorption in the cited studies, unlike the effect a high-fat meal can have on sildenafil. Forgue and colleagues, 2006

A 2019 meta-analysis by Zhou and colleagues in Sexual Medicine compared daily and on-demand tadalafil in four randomized trials with 1,035 participants treated for at least 24 weeks. Daily treatment produced a statistically greater improvement in the erectile-function domain of the IIEF, called IIEF-EF. The mean difference was 1.24 points; 95% confidence interval, 0.03–2.44; p = 0.04.

The proportion of successful intercourse attempts, assessed with Sexual Encounter Profile question 3 (SEP3), also improved more with daily treatment: a mean difference of 8.19 percentage points; 95% confidence interval, 2.09–14.29; p = 0.009. SEP3 measures the percentage of attempts completed successfully, not an eight-point change on the IIEF questionnaire.

Treatment-emergent adverse events were less frequent overall with the daily schedule: odds ratio 0.73; 95% confidence interval, 0.56–0.96; p = 0.02. An odds ratio below one indicates lower odds, not an identical reduction in absolute risk. The authors also noted limitations, including differences in doses and baseline erectile dysfunction severity across the trials. Zhou and colleagues, 2019

What the effectiveness studies show

Erectile dysfunction: daily or on demand?

Brock and colleagues combined 17 placebo-controlled on-demand studies and four once-daily studies in a descriptive analysis published in the Journal of Sexual Medicine in 2016. The analysis included 4,354 men followed for 12 weeks.

Both 5 mg once daily and 10–20 mg on demand significantly improved IIEF erectile-function scores compared with placebo (p < 0.02) across the clinical subgroups examined. These included men with diabetes, cardiovascular disease, hypertension, and high blood lipids. Because the comparison combined separate trial databases, it was not a single randomized head-to-head test of the schedules. Brock and colleagues, 2016

A 2018 study by Bolat and colleagues in the International Journal of Impotence Research compared 5 mg daily in 31 men with 20 mg on demand in 32 men. All 63 participants had diabetes and erectile dysfunction, and treatment lasted three months. Both schedules improved IIEF scores and urinary symptoms in patients younger than 65. Daily treatment produced greater improvements in ejaculatory function and LUTS. These overlapping symptoms may help guide an individual treatment choice. Bolat and colleagues, 2018

Longer-term evidence comes from Jiang and colleagues’ randomized, open-label postmarketing study, published in the Asian Journal of Andrology in 2024. It followed 635 Chinese men with erectile dysfunction for two years. Participants initially received either 2.5 or 5 mg daily for three months, then continued on 5 mg daily for another 21 months.

At 24 months, the mean IIEF-EF improvement was 8.6 points; 95% confidence interval, 8.1–9.0; p < 0.001. A score in the normal erectile-function range, defined as at least 26, was reported in 48.0% of patients. Treatment-emergent adverse events remained stable between months 12 and 24. The study supports sustained benefit and provides longer-term safety observations in this population, without establishing unlimited safety for every patient or longer duration. Jiang and colleagues, 2024

Enlarged prostate and lower urinary tract symptoms

Cui and colleagues’ 2021 meta-analysis in Frontiers in Medicine included 15 randomized trials and 9,525 patients: 4,937 received tadalafil and 4,588 placebo. The regimen was 5 mg once daily for 12 weeks.

Tadalafil reduced IPSS by an additional mean 1.97 points compared with placebo; 95% confidence interval, −2.24 to −1.70; p < 0.00001. However, maximum urinary flow did not improve significantly: mean Qmax difference 0.11 mL/s; 95% confidence interval, −0.41 to 0.63; p = 0.68. Patients can therefore experience fewer symptoms without a measurable increase in maximum flow. Cui and colleagues, 2021

Tadalafil received FDA approval for BPH symptoms in 2011 and also has an indication for men with both erectile dysfunction and BPH. Improvement in symptoms should not be confused with proof that it shrinks the prostate or prevents all complications of obstruction.

Pulmonary arterial hypertension: the PHIRST trial

The pivotal PAH trial was PHIRST, short for Pulmonary Arterial Hypertension and Response to Tadalafil. Galiè and colleagues published it in Circulation in 2009.

The study enrolled 405 patients with idiopathic PAH or PAH associated with other conditions. Some were treatment-naive; others were already taking bosentan. They were randomized to placebo or tadalafil at 2.5, 10, 20, or 40 mg once daily for 16 weeks.

At 40 mg, the placebo-adjusted improvement in six-minute walking distance was 33 meters; 95% confidence interval, 15–50 m; p < 0.01. The improvement was larger in patients not taking bosentan: 44 m; 95% confidence interval, 20–69 m. Among those already taking bosentan, it was 23 m; 95% confidence interval, −2 to 48 m. Because the latter interval includes no difference, that subgroup estimate was less certain.

The 40 mg dose also reduced clinical worsening by a relative 68% (p = 0.038) and improved health-related quality of life (p = 0.041). The 68% figure is a relative reduction, not a reduction of 68 percentage points. The 40 mg regimen was subsequently approved as Adcirca. These findings concern a different condition, dose, and population from Cialis treatment for erectile dysfunction or BPH. Galiè and colleagues, 2009

Patient and partner preferences

A medicine’s usefulness also depends on how it fits into everyday life. Gong and colleagues’ 2017 systematic review and meta-analysis in International Urology and Nephrology included 16 controlled studies directly comparing tadalafil with sildenafil.

Overall efficacy and adverse-event rates were similar. Psychological outcomes, including sexual confidence, favored tadalafil, and patients and partners preferred it significantly more often (p < 0.05). Gong and colleagues, 2017

A 2024 review by Manfredi and colleagues in Minerva Urology and Nephrology included 14 randomized trials involving 6,841 patients, plus four post-hoc analyses. Across the relevant studies, 66–73% preferred tadalafil to sildenafil (p < 0.05). Among those preferring tadalafil, 55–67% cited the ability to have an erection long after taking the medicine as the main reason.

Meanwhile, 57–59% preferred on-demand tadalafil to a three-times-weekly schedule (p < 0.05). Every included trial had a high risk of bias. Preferences can matter for adherence and satisfaction, but they do not establish clinical superiority. Differences in populations and study methods also limit how directly these percentages can be compared. Manfredi and colleagues, 2024

Side effects: what to expect

Tadalafil shares many side effects with other PDE5 inhibitors. They generally depend on dose, and many are mild or moderate. Some settle over time or after a prescribed dose adjustment. New or substantial symptoms still deserve assessment rather than an assumption that they will pass.

Common side effects include:

Headache. In Montorsi and colleagues’ open-label extension study, 15.8% of 1,173 men reported headache during up to 24 months of treatment with 5–20 mg as needed. Headaches are generally dose-related and may ease with continued treatment. Montorsi and colleagues, 2004
Facial flushing and warmth, associated with blood vessel dilation and more common at higher doses.
Dyspepsia, or indigestion. Brock and colleagues’ analysis examined adverse events among tadalafil users; it did not establish that indigestion is more common than with every other PDE5 inhibitor or prove PDE11 inhibition is its cause. Brock and colleagues, 2009
Nasal congestion.
Back pain and muscle aches. These are recognized tadalafil-associated symptoms and are often temporary. Their cause is not established simply by tadalafil’s activity against PDE11. The cited investigation examined possible explanations rather than proving that mechanism. Seftel and colleagues, 2005
Pain in the arms or legs.

Less common but particularly important problems include:

Low blood pressure. Tadalafil’s vascular effects can lower blood pressure, and combining it with nitrates such as nitroglycerin is contraindicated. Kloner and colleagues pooled 72 phase II–IV studies involving 22,825 patients with erectile dysfunction or BPH; the placebo-controlled analysis included 15,030. Across indications, hypotension-related events occurred in about 0.6–1.5%. Among people taking at least one antihypertensive, tadalafil did not significantly increase these events versus placebo (p values ≥ 0.7386). However, an increase occurred in the on-demand erectile dysfunction group not taking antihypertensives (p = 0.0070). Major cardiovascular events also did not increase significantly in the included antihypertensive groups. The analysis excluded alpha-blockers and does not override interaction warnings. Kloner and colleagues, 2022
Nonarteritic anterior ischemic optic neuropathy, or NAION. This rare problem can damage the optic nerve. A previous episode requires careful assessment; under the US label, treatment is considered only if anticipated benefit outweighs risk. Sudden loss of vision requires urgent care.
Sudden reduction or loss of hearing. Stop taking tadalafil and seek prompt medical attention if this occurs.
Priapism. An erection lasting more than four hours is an emergency. Delay can lead to permanent damage to erectile tissue and erectile function.

Before prescribing, the clinician reviews cardiovascular status, relevant conditions, and all concurrent medicines. A complete medication list is particularly important for identifying contraindicated combinations such as nitrates.

Who is tadalafil usually prescribed for?

Erectile dysfunction

Tadalafil is FDA-approved for erectile dysfunction in adult men. It may be considered when a confirmed erectile problem affects quality of life. Assessment also includes cardiovascular health, because erectile dysfunction can be an early sign of vascular disease. A systematic review and meta-analysis examined its association with later cardiovascular events. Zhao and colleagues, 2019

Madeira and colleagues’ network meta-analysis was published online in 2020 and in the 2021 volume of World Journal of Urology. It included 179 randomized trials and 50,620 patients. Network analyses combine direct and indirect comparisons between treatments. Tadalafil 10 and 20 mg ranked highly for IIEF improvement, with reported ranking values of 73% and 76%. Those values are statistical rankings, not a patient’s probability of treatment success.

Taking effectiveness and safety together, the authors favored low-dose sildenafil and tadalafil among leading treatment options. The rankings still depend on the quality and comparability of the underlying studies. Madeira and colleagues

Suitability depends on cardiovascular status, other medicines, and the causes of erectile dysfunction. FDA-approved indications also include BPH and PAH. Prescribing for an unapproved indication is an off-label clinical decision, not evidence that the additional use has been established.

Benign prostatic hyperplasia and LUTS

Tadalafil is approved for the signs and symptoms of BPH and for men who have both BPH and erectile dysfunction. Treating both symptom areas may be useful when urinary symptoms have been properly assessed.

The approved BPH dose is 5 mg once daily, with individual factors determining suitability. Jiang’s two-year study offers longer follow-up than many short trials, but it enrolled men with erectile dysfunction. It is not a condition-specific long-term safety study of every BPH population.

Urinary symptoms still need evaluation while tadalafil is being considered or used. Depending on the situation, this may include a prostate-specific antigen (PSA) measurement. PSA alone can neither confirm nor exclude prostate cancer.

Pulmonary arterial hypertension

Adcirca uses a 40 mg once-daily regimen for PAH in adults to improve exercise capacity. PHIRST also found fewer clinical-worsening events during its 16-week study. The Adcirca prescribing information should guide product-specific use.

PAH requires specialist care, commonly involving pulmonary or cardiovascular specialists. Its dose, patient population, and monitoring differ substantially from treatment for erectile dysfunction or BPH.

Who should not take tadalafil?

The risks need to be assessed before a prescription is issued. The following list includes both contraindications and circumstances requiring avoidance, dose adjustment, or careful assessment. Those categories have different implications.

Organic nitrates and nitric-oxide-releasing recreational substances can cause a severe, potentially life-threatening blood pressure drop when combined with tadalafil. Examples include nitroglycerin, isosorbide mononitrate, isosorbide dinitrate, and amyl nitrite.
Soluble guanylate cyclase stimulators such as riociguat are also contraindicated because of their combined blood-pressure-lowering effects.
A serious hypersensitivity reaction to tadalafil or a formulation ingredient rules out use of that product.
With severe hepatic impairment, classified as Child-Pugh C, tadalafil use is not recommended. Liver disease can alter drug handling, and severe impairment is insufficiently studied.
Severe renal impairment requires indication-specific decisions. With creatinine clearance below 30 mL/min, once-daily Cialis is not recommended; the PAH product Adcirca should be avoided. Restricted on-demand Cialis dosing is a separate prescribing question, not permission to continue an ordinary daily schedule.
If sexual activity is inadvisable because of unstable cardiovascular disease, such as unstable angina, a recent heart attack, or uncontrolled arrhythmias, tadalafil should not be prescribed for erectile dysfunction without appropriate cardiovascular assessment.
Previous NAION requires particular caution because another episode may threaten vision.
Marked hypotension, below 90/50 mmHg, raises concern about a further blood pressure fall.
Strong CYP3A4 inhibitors, such as ketoconazole or ritonavir, can markedly increase tadalafil exposure. Dose limits and other precautions depend on the product and indication.

The list is not exhaustive. The decision rests on the overall clinical picture, complete medication list, cardiovascular history, and accompanying conditions.

Alpha-blockers deserve specific attention because their blood pressure effects can add to tadalafil’s. For erectile dysfunction, US Cialis labeling describes starting at the lowest recommended dose only after alpha-blocker treatment is stable. The same label does not recommend combining Cialis with an alpha-blocker to treat BPH. These are indication-specific precautions, not a universal combination protocol.

Which assessments make sense before treatment?

Baseline assessment helps determine whether treatment is suitable and provides context for subsequent changes. The required tests depend on symptoms, conditions, medicines, and indication. The items below are possibilities, not a mandatory tadalafil laboratory package.

Lipids and cardiovascular risk, sometimes including apolipoprotein B (ApoB). Erectile dysfunction is associated with atherosclerotic vascular disease. LDL cholesterol and, where useful, ApoB can contribute to the broader risk assessment. They complement history, examination, and other risk factors rather than determining whether tadalafil will work. Zhao and colleagues, 2019; background on cardiovascular biomarkers and LDL cholesterol.
Blood pressure. A baseline measurement identifies pre-existing hypotension and can affect treatment selection or dose. It is not a blood test, but it is directly relevant to a medicine that dilates blood vessels.
High-sensitivity C-reactive protein (hs-CRP). This can add context in selected cardiovascular risk assessments. It neither establishes a vascular cause of erectile dysfunction nor serves as a routine prerequisite for tadalafil. Background on hs-CRP
Kidney function. Estimated glomerular filtration rate (eGFR) describes estimated filtration, while the label’s dose restrictions use creatinine clearance. These measures are not automatically interchangeable. For creatinine clearance below 30 mL/min, daily Cialis is not recommended; PAH prescribing has its own restrictions. Background on eGFR
Liver assessment, sometimes including ALT, AST, and GGT. Tadalafil is mainly metabolized by CYP3A4 in the liver. Liver disease can affect treatment decisions. Normal enzyme results alone do not demonstrate normal drug clearance or rule out every relevant liver condition. Background on liver biomarkers
Total testosterone, with free testosterone when appropriate. Erectile dysfunction often has several causes, including hypogonadism. Assessing a possible hormonal contribution avoids attributing everything to blood vessels or psychological factors. Confirmed deficiency may need separate management. Background on free testosterone and total testosterone.
Total PSA. This may help evaluate prostate symptoms or provide a baseline when prostate testing is otherwise appropriate. It is not mandatory for every tadalafil prescription. Tadalafil should not be assumed to produce the predictable PSA suppression associated with 5-alpha-reductase inhibitors. Background on total PSA
Fasting glucose and HbA1c. Diabetes commonly accompanies erectile dysfunction, with vascular and nerve changes potentially contributing. Assessing glucose regulation may identify a condition requiring its own treatment. HbA1c reflects longer-term blood glucose. Research on diabetes and erectile dysfunction; background on glucose and HbA1c.

For a man with erectile dysfunction, cardiovascular, hormonal, metabolic, kidney, and sometimes prostate assessment can help establish the full picture. Further background covers hormonal markers related to libido and fertility and cardiovascular markers. These background pages are not reasons to order every test. The clinician selects the investigations relevant to the person and question.

What blood tests can show during treatment

Follow-up testing should address an actual clinical question. If prostate assessment is already indicated, an earlier PSA result helps interpret subsequent measurements. In Donatucci and colleagues’ one-year open-label extension, mean PSA rose from 1.6 ± 1.3 to 1.8 ± 1.4 ng/mL; the study therefore does not support a claim that tadalafil lowers PSA. Without an untreated comparison group in that extension, the change cannot simply be attributed to the drug. Donatucci and colleagues, 2011

Tadalafil does not directly stimulate the hormonal pathway linking the hypothalamus, pituitary, and testes. In a small uncontrolled study of 20 men taking it on demand for 12 months, total and free testosterone did not change significantly, while estradiol fell and the testosterone-to-estradiol ratio increased. This preliminary finding allows a hypothesis about indirect hormonal effects; it does not establish tadalafil as a hormone treatment or guarantee stable hormones in every user. Pilot study of hormone changes

Kidney measures, including creatinine and eGFR, and liver assessment may be useful when baseline disease, new symptoms, or a dose change make them relevant. Repeat lipid testing or other cardiovascular assessment may address overall vascular risk rather than monitor tadalafil itself.

Useful follow-up is therefore tied to the initial findings and clinical course. A large trial record does not create a requirement for every patient to repeat a broad panel at fixed intervals, nor does it eliminate the need to investigate a new problem.

Frequently asked questions

How long does tadalafil work?

Its half-life is about 17.5 hours, much longer than that of sildenafil or vardenafil. A single on-demand dose, commonly 10 or 20 mg in the trials, can support erectile function for up to 36 hours. This means a window in which a response to sexual stimulation may be easier, not a continuous erection or an identical duration for everyone. Study of the 24- and 36-hour response

With daily 2.5–5 mg dosing, steady state is reached after approximately five days. Exposure then follows a repeated daily pattern, without requiring sex to be timed closely to an individual dose. Forgue and colleagues, 2006

How does it differ from sildenafil?

Both inhibit PDE5 through the same basic pathway. Absorption, elimination, and duration differ: tadalafil has a half-life of about 17.5 hours versus around four hours for sildenafil. Food has little effect on tadalafil absorption, whereas a high-fat meal can delay sildenafil absorption. Background comparison

Tadalafil has an approved daily erectile dysfunction schedule and a separate BPH indication. That does not imply sildenafil lacks regularly scheduled uses in other conditions.

Gong and colleagues’ 2017 review of 16 direct comparisons found similar overall efficacy and adverse-event rates. Patients and partners preferred tadalafil more often (p < 0.05), with greater sexual confidence and flexibility contributing. Population and study-design differences limit how broadly those preferences can be applied. Gong and colleagues, 2017

Is compounded tadalafil the same as Cialis?

No. A compounded preparation should not automatically be treated as equivalent to Cialis or Adcirca, the approved brand-name tadalafil products.

Licensed pharmacies prepare compounded medicines, but the preparations do not have their own FDA approval. The FDA has not evaluated their product-specific safety, effectiveness, and quality in the same way as approved manufactured medicines. Formulation, concentration, and inactive ingredients may differ.

A prescriber or pharmacist can explain the regulatory status of a specific product and the available alternatives. Approved generic tablets should not be confused with compounded preparations.

Can tadalafil be taken daily?

Yes, for an appropriate indication and prescribed regimen. Daily erectile dysfunction doses are 2.5 or 5 mg; the standard BPH dose is 5 mg once daily.

Steady state is reached after about five days. Daily exposure reduces the need to coordinate sexual activity with each dose.

Zhou and colleagues’ 2019 meta-analysis of four trials and 1,035 participants found a greater IIEF-EF improvement with daily rather than on-demand treatment after at least 24 weeks: mean difference 1.24 points; 95% confidence interval, 0.03–2.44; p = 0.04. Treatment-emergent adverse events were less frequent overall: odds ratio 0.73; 95% confidence interval, 0.56–0.96; p = 0.02. Differences between the trials and their doses matter when interpreting this modest average advantage. Zhou and colleagues, 2019

Does tadalafil lower blood pressure?

It can modestly lower both systolic and diastolic pressure through blood vessel dilation.

Kloner and colleagues’ pooled analysis included 72 trials and 22,825 patients. It did not find a significant increase in hypotension-related events among participants also taking conventional antihypertensive medicines. That result applies to the studied combinations and populations; alpha-blockers were excluded. It does not establish the safety of every blood-pressure-lowering combination. Kloner and colleagues, 2022

Nitrates and guanylate cyclase stimulators such as riociguat remain contraindicated because of the potential for severe hypotension.

What should be avoided while taking it?

Nitrates and recreational nitrites, including nitroglycerin, isosorbide mononitrate, and amyl nitrite, must not be combined with tadalafil. The resulting blood pressure fall can be severe. Riociguat is another contraindicated combination.

Grapefruit can inhibit CYP3A4 and may increase tadalafil exposure. The specific study cited here was conducted in rats, so it cannot quantify the interaction in people. Shen and colleagues, 2020

Large amounts of alcohol can compound the blood pressure effect. Strong CYP3A4 inhibitors, including some antifungal medicines and HIV protease inhibitors, can substantially raise tadalafil exposure. Their use may require product-specific dose restrictions or other changes. Review the complete medication list before treatment rather than treating these as interchangeable interactions.

Does it affect testosterone?

Tadalafil does not directly stimulate the hypothalamic-pituitary-gonadal axis or function as testosterone replacement. That does not rule out indirect hormonal changes. The small pilot discussed above found no significant total or free testosterone change but did find a change in estradiol and the hormone ratio.

Low testosterone can contribute to erectile dysfunction and may warrant assessment. When hypogonadism and erectile dysfunction coexist, tadalafil can address the erectile response while separately justified hormone treatment addresses the deficiency. Background on total testosterone

Which blood tests are useful before treatment?

Depending on the situation, assessment may include creatinine and kidney function for dose selection, liver assessment, lipids and sometimes ApoB, testosterone testing, selected PSA testing, and glucose or HbA1c. Blood pressure should also be considered.

A reason to evaluate the prostate does not mean every patient needs PSA testing. The selection depends on symptoms and indication. Background on eGFR, total PSA, and total testosterone.

Important safety information

Tadalafil is a prescription medicine. Nitrates, riociguat, and serious hypersensitivity are important contraindications. An erection lasting more than four hours, sudden vision loss, or sudden hearing loss requires urgent medical attention. Alcohol and alpha-blockers can add to its blood pressure effect.

Approval depends on the product, age, and indication. Erectile dysfunction labeling should not be generalized into a statement that tadalafil is never used in women: PAH treatment includes women. Common side effects include headache, flushing, indigestion, nasal congestion, back pain, muscle pain, and limb pain.

Full US prescribing information is available through DailyMed.

How to weigh the evidence

The useful question is what a particular study measured in a particular population. A strong result for one indication does not settle another.

Daily and on-demand schedules answer different practical needs. The standard daily dose for BPH is 5 mg, while erectile dysfunction labeling includes 2.5 and 5 mg.
Improvement in an erectile-function questionnaire or urinary symptom score is a patient-relevant result. It does not automatically establish prevention of cardiovascular events or prostate complications.
Vascular mechanisms remain worth investigating. The older endothelial-function analysis and newer broader vascular meta-analysis have different evidence bases; both their negative and positive findings deserve context.
Statistical significance, effect size, and clinical importance are separate. The uncertain PWV unit is a reason to avoid overinterpreting that numerical estimate, not to erase the wider vascular hypothesis.
Two-year erectile dysfunction observations do not prove lifelong safety or provide direct evidence for every BPH population.
Compounded formulations, approved tablets, and orodispersible films should not be treated as interchangeable merely because they contain the same active ingredient.
Hormonal findings from a small uncontrolled pilot are preliminary. They do not make tadalafil testosterone replacement or establish a predictable effect on every user’s hormones.
Monitoring follows the clinical question. PSA, broad biomarker panels, and repeated testing are not automatically required just because someone takes tadalafil.

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Additional scientific and background sources

The following studies provide further context for dosing schedules, hormone findings, duration of benefit, and diabetes:

These background explainers are not substitutes for clinical trials or prescribing instructions: