5-HT antagonists, also known as serotonin receptor antagonists, are a class of drugs that inhibit the action of serotonin, a neurotransmitter that plays a crucial role in various physiological processes. These antagonists block the binding of serotonin to its receptors, thereby modulating its effects. There are different subtypes of serotonin receptors, and 5-HT antagonists can target specific receptor types.
Classification of 5-HT Antagonists
5-HT (serotonin) antagonists, also known as serotonin receptor antagonists or blockers, are a class of drugs that inhibit the action of serotonin. They are classified based on the specific serotonin receptors they target:
1. 5-HT3 Receptor Antagonists:
– Examples: Ondansetron, Granisetron, and Palonosetron.
– Clinical Uses: Primarily used to prevent and treat nausea and vomiting, especially associated with chemotherapy, radiation therapy, and postoperative recovery.
– Adverse Effects: Headache, constipation, and, rarely, electrocardiogram (ECG) changes. Generally well-tolerated.
2. 5-HT2 Receptor Antagonists:
– Examples: Cyproheptadine and Ketanserin.
– Clinical Uses: Limited clinical use; cyproheptadine is sometimes used for the management of migraines and serotonin syndrome.
– Adverse Effects: Sedation, anticholinergic effects, and potential cardiovascular effects.
3. 5-HT1 Receptor Antagonists:
– Examples: Pizotifen (mostly a 5-HT2 antagonist but also affects 5-HT1 receptors), Naratriptan, and Sumatriptan.
– Clinical Uses: Sumatriptan and naratriptan are used for the acute treatment of migraines, and pizotifen is used for migraine prophylaxis.
– Adverse Effects: Sumatriptan and naratriptan may cause chest pain and other cardiovascular effects. Pizotifen may cause weight gain, sedation, and anticholinergic effects.
Clinical Uses of 5-HT Antagonists
1. Nausea and Vomiting:
– 5-HT3 receptor antagonists like ondansetron are commonly used to prevent and manage chemotherapy-induced nausea and vomiting.
2. Migraines:
– Some 5-HT1 receptor antagonists, such as sumatriptan and naratriptan, are used to treat acute migraine attacks.
3. Migraine Prophylaxis:
– Pizotifen, which has 5-HT2 and 5-HT1 receptor antagonist properties, prevents migraines.
4. Serotonin Syndrome:
– Cyproheptadine, a 5-HT2 receptor antagonist, is sometimes used to treat serotonin syndrome.
5. Gastrointestinal Disorders:
  – Doctors may use 5-HT3 receptor antagonists to manage irritable bowel syndrome (IBS) and other gastrointestinal disorders.
Adverse Effects of 5-HT Antagonists
1. 5-HT3 Receptor Antagonists:
– Headache, constipation, and potential ECG changes. Generally well-tolerated.
2. 5-HT2 Receptor Antagonists:
– Sedation, anticholinergic effects (dry mouth, blurred vision), and potential cardiovascular effects.
3. 5-HT1 Receptor Antagonists:
– Sumatriptan and naratriptan may cause chest pain and other cardiovascular effects. Pizotifen may cause weight gain, sedation, and anticholinergic effects.
4. Common Adverse Effects:
– Some 5-HT antagonists may cause drowsiness, dizziness, and gastrointestinal disturbances.
5. Interactions:
Consider drug interactions, especially when combining 5-HT antagonists with other medications that affect serotonin levels.
5-HT antagonists have diverse clinical uses, ranging from managing nausea and vomiting to treating and preventing migraines. Adverse effects vary among different subclasses of 5-HT antagonists, and careful consideration of individual patient characteristics and potential drug interactions is crucial in their use.
