What is the recommended dosage of Perinorm (Cyproheptadine) for treating irritable bowel syndrome (IBS)?

Cyproheptadine (Perinorm) is Not Recommended for IBS Treatment

Cyproheptadine is not an evidence-based treatment for irritable bowel syndrome and does not appear in any major gastroenterology guidelines for IBS management. The medication you're asking about appears to be a misidentification, as "Perinorm" typically refers to metoclopramide in some regions, not cyproheptadine.

Critical Clarification

• Cyproheptadine is an antihistamine with antiserotonergic properties primarily used for allergic conditions and appetite stimulation, not IBS 1, 2
• No clinical trials or guidelines support cyproheptadine for IBS treatment 3
• The evidence-based pharmacologic options for IBS are entirely different medications 4

Evidence-Based Alternatives for IBS Management

For IBS with Constipation (IBS-C):

First-line options:

• Linaclotide 290 mcg once daily - strongly recommended with high-quality evidence for reducing abdominal pain and improving bowel movements 3
• Plecanatide 3 mg once daily - effective for both pain and constipation symptoms 3
• Lubiprostone 24 mcg twice daily - causes less diarrhea than other secretagogues, though nausea is common 4
• Tenapanor 50 mg twice daily - newer option with demonstrated efficacy 3

For IBS with Diarrhea (IBS-D):

First-line options:

• Loperamide 4-12 mg daily - effective for stool frequency and urgency, limited effect on pain 4
• Ondansetron 4 mg once daily, titrate to maximum 8 mg three times daily - highly efficacious 5-HT3 antagonist 4
• Rifaximin - non-absorbable antibiotic effective for global symptoms 4, 5

For Global IBS Symptoms and Pain:

Second-line options:

• Tricyclic antidepressants (amitriptyline 10 mg once daily, titrate to 30-50 mg) - strongest evidence for pain control and global symptoms 4, 2
• Antispasmodics (dicyclomine) - modest efficacy for abdominal pain, though anticholinergic side effects limit use 4, 1
• Peppermint oil 3-4 g/day - effective for global symptoms and pain with minimal side effects 4, 5

Common Pitfalls to Avoid

• Do not use medications without evidence basis - cyproheptadine lacks any supporting data for IBS 1, 2, 5
• Avoid anticholinergics like dicyclomine in constipation-predominant IBS - they worsen constipation 4
• Start all medications at low doses and titrate slowly to minimize side effects and improve tolerability 4, 5
• Clearly explain to patients that antidepressants are used for gut-brain modulation, not depression treatment, to improve adherence 4

Practical Algorithm

1. Identify IBS subtype (constipation-predominant, diarrhea-predominant, or mixed)
2. For IBS-C: Start with linaclotide 290 mcg daily or plecanatide 3 mg daily 3
3. For IBS-D: Start with loperamide 4 mg as needed or ondansetron 4 mg daily 4
4. For persistent pain: Add low-dose tricyclic antidepressant (amitriptyline 10 mg at bedtime) 4, 2
5. Monitor response at 4-6 weeks and adjust therapy accordingly 5