What are the uses and precautions of Cyproheptadine (antihistamine)?

Cyproheptadine: Uses and Precautions

Cyproheptadine is a first-generation antihistamine with multiple clinical applications including treatment of nonallergic rhinitis, management of PTSD-related nightmares, appetite stimulation, and treatment of serotonin syndrome, but should be used with caution due to significant sedative and anticholinergic effects. 1, 2

Primary Clinical Uses

• Nonallergic Rhinitis: Effective for controlling rhinorrhea in nonallergic rhinitis syndromes, particularly gustatory rhinitis and vasomotor rhinitis due to its anticholinergic effects 1
• Appetite Stimulation: Demonstrated efficacy as an appetite stimulant in both adults and children with poor appetite, promoting weight gain and improving body mass index 3, 4, 5
• PTSD-Related Nightmares: May reduce or eliminate nightmares in some patients with PTSD, though evidence shows mixed results with doses ranging from 2-24 mg nightly 1
• Serotonin Syndrome: Recommended for treatment of serotonin syndrome, particularly in pediatric patients at a dosage of 0.25 mg/kg per day 6
• Mast Cell Activation Disorders: Can help manage gastrointestinal symptoms in patients with mast cell activation syndrome due to its dual function as an H1 blocker and serotonin antagonist 1
• Growth Enhancement: May enhance linear growth and weight gain in children with hypopituitarism receiving growth hormone therapy 7

Dosing Information

• Adults: Typical dosing is 4 mg three times daily, with doses ranging from 4-12 mg per day for most indications 1, 2
• Children: For pediatric patients over 2 years old, dosing should be adjusted by weight; for serotonin syndrome, 0.25 mg/kg per day is recommended 6, 2
• Administration: Available as 4 mg tablets that can be divided for smaller doses, and tablets can be crushed and administered via nasogastric tube if needed 6

Precautions and Contraindications

• Sedation and CNS Effects: Causes significant sedation and may impair mental alertness, affecting activities requiring mental coordination such as driving 1, 2

• Use with Caution in Patients with:

  • History of bronchial asthma
  • Increased intraocular pressure
  • Hyperthyroidism
  • Cardiovascular disease
  • Hypertension 2

• Drug Interactions:

  • MAO inhibitors prolong and intensify anticholinergic effects
  • Additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, antianxiety agents) 2

• Contraindicated in:

  • Newborns or premature infants
  • Nursing mothers (safety not established)
  • Patients taking MAO inhibitors 2

Adverse Effects

• Common Side Effects:

  • Sedation and somnolence (most common) 3
  • Anticholinergic effects (dry mouth, constipation, urinary retention) 1
  • Increased appetite and weight gain (can be therapeutic in some cases) 4, 5

• Serious Concerns:

  • Cognitive decline, particularly in elderly patients 1
  • Potential for toxicity in overdose (documented fatalities) 8
  • May occasionally produce excitation, particularly in young children 2
  • Visual hallucinations (rare) 1

Special Populations

• Pediatric Use: Safety not established in children under 2 years of age 2
• Geriatric Use: Use with caution, starting at lower doses due to increased risk of adverse effects; particular concern for cognitive decline with anticholinergic effects 1, 2
• Pregnancy: Category B - no evidence of harm to fetus in animal studies, but human studies cannot rule out possibility of harm 2

Clinical Pearls

• First-generation antihistamines like cyproheptadine can cause performance impairment even without subjective awareness of sedation 1
• Due to prolonged plasma half-life (approximately 16 hours), sedative effects cannot be eliminated by bedtime-only administration 1
• When used for appetite stimulation, significant improvements in body mass index can be seen within 4-8 weeks of treatment 3, 5
• For PTSD-related nightmares, effects may be seen within a few days of starting treatment 1