Promethazine Hydrochloride
Generic Details
Generic Name
Promethazine Hydrochloride
Other Names
- Phenergan
Drug Class
- Antihistamine
- Antiemetic
Chemical Formula
C17H21ClN2S
Molecular Weight
320.88 g/mol
Mechanism of Action
- Blocks histamine H1 receptors
- Antagonizes dopamine D2 receptors
Indications
- Allergic reactions
- Nausea and vomiting
- Sedation
- Motion sickness
Common Dosage Forms
- Tablet
- Syrup
- Injection
Typical Dosage
- 12.5-25 mg every 4-6 hours as needed
Pediatric Dosage
- Consult pediatrician for appropriate dosing based on weight
Geriatric Dosage
- Use lower end of dosage range due to increased sensitivity in elderly
Side Effects
- Drowsiness
- Dry mouth
- Blurred vision
- Constipation
- Urinary retention
Contraindications
- Hypersensitivity to promethazine
- Comatose state
- Respiratory depression
Pregnancy Category
- C - Risk cannot be ruled out
Lactation Safety
- Caution advised, may excrete in breast milk
Drug Interactions
- CNS depressants
- Anticholinergic drugs
- MAO inhibitors
Overdose Symptoms
- Severe drowsiness
- Agitation
- Seizures
- Respiratory depression
Antidote for Overdose
- Supportive care
- Activated charcoal
- Physostigmine in severe cases
Storage Conditions
- Store at room temperature away from moisture and heat
Pharmacokinetics
- Absorption: Well absorbed orally
- Distribution: Widely distributed in the body, crosses the blood-brain barrier
- Metabolism: Hepatic via CYP2D6
- Excretion: Primarily renal excretion
Precautions
- Use caution in patients with respiratory conditions
- Avoid alcohol consumption
- Monitor for extrapyramidal symptoms
Warnings
- May cause drowsiness, do not drive or operate machinery until effects are known
Others
- Not recommended for children under 2 years old