PERIACTIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PERIACTIN (PERIACTIN).
Cyproheptadine is a first-generation antihistamine with anticholinergic and antiserotonergic properties. It acts as a competitive antagonist at histamine H1 receptors and serotonin 5-HT2 receptors, thereby inhibiting histamine-mediated allergic symptoms and serotonin-mediated effects such as increased gastrointestinal motility and vascular permeability.
| Metabolism | Hepatic metabolism primarily via hydroxylation and glucuronidation; cytochrome P450 enzymes (CYP3A4, CYP2D6) are involved; elimination half-life approximately 16 hours. |
| Excretion | Renal (40-50% as metabolites, <5% unchanged); biliary/fecal (minor, ~10-20%) |
| Half-life | 10-12 hours terminal elimination half-life; steady-state reached in 2-3 days |
| Protein binding | 90-95% bound to plasma proteins (albumin) |
| Volume of Distribution | 10-20 L/kg (large, indicating extensive tissue distribution) |
| Bioavailability | Oral: 50-60% due to first-pass metabolism |
| Onset of Action | Oral: 30-60 minutes; parenteral not available in US |
| Duration of Action | 4-6 hours for antihistamine effect; sedative effects may persist 6-8 hours |
4 mg orally three times daily; adjust as needed. Maximum: 32 mg/day.
| Dosage form | SYRUP |
| Renal impairment | For GFR < 15 mL/min: use with caution and consider reducing dose. No specific guidelines available. |
| Liver impairment | Child-Pugh Class C: contraindicated. Class A or B: use with caution, reduce dose by 50%. |
| Pediatric use | 2-6 years: 2 mg orally 2-3 times daily; 7-14 years: 4 mg orally 2-3 times daily. Maximum daily dose: 0.5 mg/kg. |
| Geriatric use | Start at 2 mg orally twice daily; increase gradually. Monitor for sedation, confusion, and anticholinergic effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PERIACTIN (PERIACTIN).
| Breastfeeding | Excretion into breast milk is unknown; however, due to its anticholinergic properties, it may potentially reduce milk production. M/P ratio not determined. Caution is advised; consider benefit-risk, or use alternative agents. |
| Teratogenic Risk | Cyproheptadine is a pregnancy category B drug. Animal studies have not demonstrated fetal risk, but adequate human studies in pregnant women are lacking. First trimester: No known teratogenic effects. Second and third trimesters: Limited data; potential for anticholinergic effects (e.g., tachycardia, constipation) in fetus if used near term. Avoid use during pregnancy unless clearly needed. |
■ FDA Black Box Warning
None
| Serious Effects |
Newborns or premature infants; breastfeeding; narrow-angle glaucoma; stenosing peptic ulcer; symptomatic prostatic hypertrophy; bladder neck obstruction; pyloroduodenal obstruction; concomitant use with monoamine oxidase inhibitors (MAOIs); history of severe allergic reactions to cyproheptadine.
| Precautions | Use with caution in patients with glaucoma, history of bronchial asthma, hyperthyroidism, cardiovascular disease, hypertension, or prostatic hypertrophy; may impair mental alertness and cause drowsiness; anticholinergic effects may exacerbate symptoms of narrow-angle glaucoma, pyloroduodenal obstruction, or bladder neck obstruction; elderly patients are more sensitive to anticholinergic effects; use in neonates and premature infants is contraindicated due to increased risk of sudden infant death syndrome. |
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| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and signs of anticholinergic toxicity (e.g., urinary retention, blurred vision). For fetus, monitor heart rate and growth if used chronically. No specific fetal monitoring required with short-term use. |
| Fertility Effects | Cyproheptadine may suppress prolactin secretion, theoretically impairing ovulation and lactation. Animal studies have shown no significant fertility impairment, but human fertility data are lacking. |