Cyproheptadine

5HT2A Antagonist·Psychiatry - Acute Calming & Sedation

Allergic dermatoses, severe pruritus

ANTIDOTEPeriactin4 mg tabletS4TGA

Max Dose

32 mg/day

Half-life

16 h

Serotonin Synd.

RESCUE DRUG

Sedation

PROFOUND

Rapid Summary

Overview

First-generation antihistamine with exceptionally potent anti-serotonergic (5-HT2A) properties. The definitive oral antidote for life-threatening Serotonin Syndrome.

Maximum Dose

Max 32 mg/day (Adults).

Clinical Focus

Only available orally. If a patient is seizing or comatose from Serotonin Syndrome, the tablets must be crushed and given via NGT.

Bottom Line

Cyproheptadine is a first-generation antihistamine used as an appetite stimulant and serotonin syndrome antidote, but causes significant sedation and weight gain.

Formulation & Access

Brand Names

Periactin

Oral Routes

Tablets (4 mg).

Prescribing & PBS

Pharmacy Medicine (S3) or Prescription (S4) depending on indication.

Indications & Use

Primary

TGA

Allergic dermatoses, severe pruritus.

Off-Label

OFF

Serotonin Syndrome antidote, appetite stimulation in anorexia, SSRI-induced sexual dysfunction.

Clinical Place

Emergency toxicology rescue drug for SSRI/Tramadol/MAOI overdoses presenting with clonus and hyperthermia.

Quick reference

Class & Role

5HT2A Antagonist — First-generation antihistamine with exceptionally potent anti-serotonergic (5-HT2A) properties.

Route / Formulation

Tablets (4 mg). (Periactin)

Usual Dose & Max

PO / NGT 12 mg STAT, followed by 2 mg every 2 hours until symptoms resolve (or 8 mg q6h). Max 32 mg/day.

Key Indication Doses

Serotonin Syndrome (Antidote): PO / NGT 12 mg STAT, followed by 2 mg every 2 hours until symptoms resolve (or 8 mg q6h). Max 32 mg/day. Severe Pruritus / Urticaria: PO 4-8 mg TDS. Appetite Stimulation (Off-Label): PO 2-4 mg TDS.

Best Uses

Cyproheptadine is a first-generation antihistamine used as an appetite stimulant and serotonin syndrome antidote, but causes significant sedation and weight gain.

Avoid / Cautions

Narrow-angle glaucoma, severe BPH/urinary retention, concurrent MAOI use (paradoxical, but standard for most antihistamines), neonates. Pregnancy Category A.

Key Risks

Neurological: Profound sedation, dizziness, confusion, paradoxical excitation in children. Gastrointestinal: Intense appetite stimulation, weight gain, dry mouth (anticholinergic effect). Genitourinary: Urinary retention.

Key Interactions

Additive CNS depression with Benzodiazepines, Alcohol, and Opioids. Additive anticholinergic burden with TCAs and Antipsychotics.

Monitoring

In Serotonin Syndrome, monitor core temperature, rigidity, and clonus strictly. Ensure NGT placement is correct before pushing crushed tablets.

Clinical Pearl

Because Serotonin Syndrome causes rigidity, altered consciousness, and hyperthermia, patients often cannot swallow pills safely. Crushing Cyproheptadine and flushing it down a nasogastric tube is a mandatory ICU skill.

Access

Periactin4 mg tablet

Brand: Periactin
Formulation: Tablets (4 mg)

Cyproheptadine

5HT2A Antagonist·Psychiatry - Acute Calming & Sedation

Allergic dermatoses, severe pruritus

ANTIDOTEPeriactin4 mg tabletS4TGA

Max Dose

32 mg/day

Half-life

16 h

Serotonin Synd.

RESCUE DRUG

Sedation

PROFOUND

Rapid Summary

Overview

First-generation antihistamine with exceptionally potent anti-serotonergic (5-HT2A) properties. The definitive oral antidote for life-threatening Serotonin Syndrome.

Maximum Dose

Max 32 mg/day (Adults).

Clinical Focus

Only available orally. If a patient is seizing or comatose from Serotonin Syndrome, the tablets must be crushed and given via NGT.

Bottom Line

Cyproheptadine is a first-generation antihistamine used as an appetite stimulant and serotonin syndrome antidote, but causes significant sedation and weight gain.

Formulation & Access

Brand Names

Periactin

Oral Routes

Tablets (4 mg).

Prescribing & PBS

Pharmacy Medicine (S3) or Prescription (S4) depending on indication.

Indications & Use

Primary

TGA

Allergic dermatoses, severe pruritus.

Off-Label

OFF

Serotonin Syndrome antidote, appetite stimulation in anorexia, SSRI-induced sexual dysfunction.

Clinical Place

Emergency toxicology rescue drug for SSRI/Tramadol/MAOI overdoses presenting with clonus and hyperthermia.

Quick reference

Class & Role

5HT2A Antagonist — First-generation antihistamine with exceptionally potent anti-serotonergic (5-HT2A) properties.

Route / Formulation

Tablets (4 mg). (Periactin)

Usual Dose & Max

PO / NGT 12 mg STAT, followed by 2 mg every 2 hours until symptoms resolve (or 8 mg q6h). Max 32 mg/day.

Key Indication Doses

Best Uses

Cyproheptadine is a first-generation antihistamine used as an appetite stimulant and serotonin syndrome antidote, but causes significant sedation and weight gain.

Avoid / Cautions

Narrow-angle glaucoma, severe BPH/urinary retention, concurrent MAOI use (paradoxical, but standard for most antihistamines), neonates. Pregnancy Category A.

Key Risks

Key Interactions

Additive CNS depression with Benzodiazepines, Alcohol, and Opioids. Additive anticholinergic burden with TCAs and Antipsychotics.

Monitoring

In Serotonin Syndrome, monitor core temperature, rigidity, and clonus strictly. Ensure NGT placement is correct before pushing crushed tablets.

Clinical Pearl

Access

Periactin4 mg tablet

Brand: Periactin
Formulation: Tablets (4 mg)