Promethazine Hydrochloride (Injection)
Generic Details
Generic Name
Promethazine Hydrochloride Injection
Other Names
- Phenergan Injection
Drug Class
- Antihistamine
- Antiemetic
Chemical Formula
C17H21ClN2S
Molecular Weight
320.88 g/mol
Mechanism of Action
- Blocks histamine H1 receptors
- Inhibits the binding of dopamine to D2 receptors in the brainstem
Indications
- Allergic reactions
- Nausea and vomiting
- Motion sickness
- Sedation
- Preoperative sedation
Common Dosage Forms
- Injection
Typical Dosage
- 12.5-25 mg every 4-6 hours as needed
Pediatric Dosage
- 0.25-1 mg/kg/dose every 6 hours as needed
Geriatric Dosage
- Lower doses may be required due to age-related decrease in liver and kidney function
Side Effects
- Drowsiness
- Dizziness
- Blurred vision
- Dry mouth
- Constipation
- Urinary retention
Contraindications
- Hypersensitivity to promethazine
- Coma
- CNS depression
- Respiratory depression
- Nursing mothers
Pregnancy Category
- C - Risk cannot be ruled out
Lactation Safety
- Not recommended during breastfeeding due to potential risks to the infant
Drug Interactions
- Alcohol
- CNS depressants
- Anticholinergic drugs
Overdose Symptoms
- Extreme drowsiness
- Confusion
- Hallucinations
- Convulsions
- Coma
Antidote for Overdose
- No specific antidote, manage symptoms and provide supportive care
Storage Conditions
- Store at controlled room temperature (20-25°C)
Pharmacokinetics
- Absorption: Rapidly absorbed after intramuscular or intravenous injection
- Distribution: Widely distributed in the body, crosses blood-brain barrier
- Metabolism: Primarily hepatic via sulfoxidation and glucuronidation
- Excretion: Mainly via urine as metabolites
Precautions
- Use with caution in patients with asthma, COPD, glaucoma, or hepatic impairment
Warnings
- Risk of respiratory depression, especially in children under 2 years old
- Avoid use in pediatric patients for treatment of nausea/vomiting unless other options have failed
Others
- May cause tissue necrosis if injected subcutaneously