What it's for (Indications)
- Promethazine HCl is used for the management of allergies, including minor transfusion reactions.
- It is also indicated for the treatment of nausea, vertigo, and motion sickness.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | For **Allergy (Adults)**: The average oral dose is 25 mg taken before retiring; alternatively, 12.5 mg may be taken before meals and at bedtime if necessary. Single 25 mg doses at bedtime or 6.25 to 12.5 mg taken three times daily may suffice. Dosage should be adjusted to the smallest amount adequate to relieve symptoms. For minor transfusion reactions of an allergic nature, 25 mg may be administered. For **Motion Sickness (Adults)**: The average adult dose is 25 mg taken twice daily. The initial dose should be taken 30-60 minutes before anticipated travel and repeated 8 to 12 hours later if needed. For succeeding days of travel, 25 mg is recommended upon arising and again before the evening meal. For **Children (2 years and older)**: Dosage should be adjusted to the smallest amount adequate to relieve symptoms after initiation of treatment. |
Safety & Warnings
Common Side Effects
- Common central nervous system effects include drowsiness, sedation, somnolence, dizziness, headache, fatigue, lassitude, blurred vision, confusion, disorientation, euphoria, nervousness, diplopia, insomnia, tinnitus, incoordination, tremors, excitation, and hysteria.
- Anticholinergic effects may include dry mouth and constipation.
- Serious neurological effects reported are convulsions/convulsive seizures, hyperexcitability (particularly in children), extrapyramidal reactions (e.
- g.
- , oculogyric crisis, torticollis, tongue protrusion), catatonic-like states, hallucinations, and Neuroleptic Malignant Syndrome (potentially fatal).
- Cardiovascular effects can include increased or decreased blood pressure, tachycardia, bradycardia, and faintness.
- Dermatologic reactions include photosensitivity, dermatitis, and urticaria.
- Hematologic side effects may involve leukopenia, thrombocytopenia, thrombocytopenic purpura, and agranulocytosis.
- Gastrointestinal effects can include nausea, vomiting, and jaundice.
- Respiratory issues such as asthma, nasal stuffiness, respiratory depression (potentially fatal), and apnea (potentially fatal) have been reported.
- Other adverse effects include angioneurotic edema.
Serious Warnings
- Black Box Warning: Promethazine is contraindicated for use in pediatric patients less than two years of age due to the potential for fatal respiratory depression. Extreme caution should be exercised when administering promethazine to pediatric patients 2 years of age and older, and the lowest effective dose should be used. There is also a risk of severe chemical irritation and damage to tissues, including gangrene, with inappropriate intravenous administration.
- Promethazine can cause significant drowsiness, dizziness, and blurred vision; therefore, patients should avoid driving or operating machinery and refrain from consuming alcohol during treatment.
- Use with caution in patients with a history of asthma, bronchitis, bronchiectasis, coronary artery disease, glaucoma, brain disorders (such as Reye’s syndrome or epilepsy), or difficulty urinating.
- Pregnancy data is not definite; caution is advised, and consultation with a doctor is recommended.
- Respiratory depression, potentially fatal, has been reported with promethazine, especially in pediatric patients.
- Neuroleptic Malignant Syndrome (NMS), a potentially fatal condition, has also been reported.
How it Works (Mechanism of Action)
Not explicitly provided in the available data. Promethazine is an H1-receptor blocking antihistamine with sedative, antiemetic, and anticholinergic properties.