Cyproheptadine

PERIACTIN

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Pronunciation: si-proe-HEP-ta-deen

Cyproheptadine ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Cyproheptadine ballicule

Cyproheptadine PERIACTIN mascot mnemonic cartoon — Visual mnemonic: Cyproheptadine mascot
**“Perry actin’…help to dine”**
used off-label to stimulate appetite
In actin' like a docile pet, it helps to dine on pet food
“mad as a hatter” → BBB-crossing antimuscarinic
crown resembling H1 blocking peg → antihistamine

What it isFirst-generation antihistamine with 5-HT2 antagonism; allergy, appetite stimulation and serotonin syndrome.

Why this oneIt is the agent used for serotonin syndrome, and the appetite effect is exploited deliberately.

What limits itSedation and anticholinergic burden. Weight gain is the point or the problem, depending on the patient.

Cyproheptadine molecular structure (skeletal formula) — Molecular structure: Cyproheptadine

FDA-approved for

allergy (~1961)

Off-label

appetite stimulation
serotonin syndrome
SSRI sexual dysfunction

FDA label

Read the full label on DailyMed ↗

FDA dosing	Population	Start	Target	Max
Allergic conditions (antihistamine)	Pediatrics 2–6 yr	2 mg BID–TID		12 mg/day
Allergic conditions (antihistamine)	Pediatrics 7–14 yr	4 mg BID–TID		16 mg/day
Allergic conditions (antihistamine)	Adults	4 mg TID	4–20 mg/day (typical 12–16 mg)	0.5 mg/kg/day (~32 mg)

Renal Undefined

Hepatic Undefined

Instructions

Individualize dose to patient response

Available strengths

tab 4 mg
sol 2 mg/5 mL

Contraindications

Newborn or premature infants
Nursing mothers
MAOIs (concurrently) because MAO inhibitors prolong and intensify the anticholinergic effects of antihistamines
Angle-closure glaucoma
Stenosing peptic ulcer
Symptomatic prostatic hypertrophy
Bladder neck obstruction
Pyloroduodenal obstruction
Elderly, debilitated patients

Adverse reactions

Sedation, drowsiness, dizziness
Dry mouth
Increased appetite / weight gain
Blurred vision
Anticholinergic effects (urinary retention, constipation)

Pregnancy Category B — use only if clearly needed

Lactation Contraindicated in nursing mothers

Cost

Cyproheptadine (PERIACTIN)

What pharmacies pay · NADAC 9/30/26

Strength		#/mo	generic $	CostPlus
4 mg	tab	90 TID	$6.11/mo	offered
2 mg/5 mL	sol	per unit	$0.04/mL	offered

Generic entry1982

NO BOXED WARNINGS

Principal riskSedation, anticholinergic burden and weight gain

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability4 / 4

Sedation liability3 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism2 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryB

Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.

Serotonicity

This drug is routinely called serotonergic. By Gillman’s human-effect criteria it does not raise serotonin in the synapse.

5-HT2A antagonist used as an oral antidotal treatment for serotonin toxicity.

Label contraindicationMAOIs (concurrently) because MAO inhibitors prolong and intensify the anticholinergic effects of antihistamines. The label governs prescribing; Gillman’s point concerns serotonin toxicity only.

Gillman’s four human testsA measurable SERT affinity that fails all four is not clinical serotonicity.