Octreotide: how it works, what it treats and side effects

Octreotide blocks the release of certain hormones. It is used for acromegaly, relieves flushing and diarrhea in carcinoid syndrome, and treats the severe diarrhea caused by a VIPoma. Whether injections, a depot formulation or capsules are suitable depends on the condition and on how well previous treatment has worked.

What is octreotide?

Octreotide is available under the brand names Sandostatin and Sandostatin LAR Depot, and as a capsule called Mycapssa. The drug consists of eight amino acids that form a ring, which makes it, chemically, a synthetic cyclic octapeptide. It mimics somatostatin, a hormone the body makes itself that puts the brakes on the release of various other hormones.

The body breaks down natural somatostatin within a few minutes. Octreotide lasts much longer, which is what makes it usable as a medicine. It was developed under the name SMS 201-995 and approved in the United States in 1988.

How does octreotide work?

Octreotide binds to somatostatin receptors, binding sites on hormone-releasing cells, mainly the receptor subtype 2. This inhibits the release of growth hormone and lowers insulin-like growth factor 1 (IGF-1). It also inhibits the release of messengers of the digestive system, including serotonin, vasoactive intestinal peptide (VIP) and gastrin. In conditions driven by excess hormone, octreotide can in this way relieve symptoms and influence the abnormal lab values.

Which effect matters most depends on the condition:

Condition	Effect of octreotide
Acromegaly	Octreotide lowers growth hormone and IGF-1, which improves symptoms, and can shrink pituitary tumors.
Carcinoid syndrome	Octreotide reduces serotonin and related messengers, relieving episodes of skin flushing and diarrhea.
VIPoma	Octreotide reduces severe secretory diarrhea. In this type of diarrhea, extra fluid passes into the gut.

Somatostatin analogs, the drug class octreotide belongs to, can also slow the growth of some neuroendocrine tumors. In the PROMID trial, the long-acting depot form extended the median time to tumor progression in metastatic midgut neuroendocrine tumors to 14.3 months, compared with 6.0 months on placebo. “Median” here means that by this point the tumor had progressed in half of the respective group. 1

Within their respective approved uses, depot formulations and capsules allow steady control of the disease without the need for several injections a day. The capsules are for maintenance treatment of acromegaly: they are an option when treatment with injectable somatostatin analogs has previously worked and been tolerated. The PROMID result does not show any corresponding effect of the capsules on tumor growth.

Is octreotide FDA approved?

Yes. The FDA, the US drug regulator, approved octreotide in 1988 as the short-acting Sandostatin injection. About a decade later came Sandostatin LAR Depot, given once a month. The Mycapssa capsule was approved in 2020 for maintenance treatment of acromegaly. These details refer to the United States. 2

What is octreotide prescribed for?

Octreotide is prescribed to treat acromegaly. In carcinoid syndrome it is meant to relieve flushing and diarrhea, and in a VIPoma the very severe diarrhea.

The capsules are intended for long-term maintenance treatment of acromegaly. The prerequisite is that injectable somatostatin analogs have previously worked and been tolerated.

What side effects can occur?

The prescribing information [2] lists the following common side effects:

Diarrhea, abdominal pain, nausea and gas
Pain at the injection site
Gallstones or biliary sludge
High or low blood sugar levels

More serious risks and other changes to watch for during treatment include:

Gallbladder disease with long-term use
Changes in blood sugar and thyroid function
A slowed heartbeat and changes in the heart’s electrical conduction