| name | Promethazine |
| Classification | Antihistamine, Antiemetic, Anticholinergic, Sedative |
| Pharmacokinetics | Promethazine is rapidly absorbed after oral administration. Peak plasma concentrations are typically reached within 1-4 hours. It is extensively metabolized in the liver, primarily by CYP2D6 and CYP3A4. The major metabolite, N-desmethylpromethazine, also exhibits antihistaminic and antiemetic activity. Elimination half-life varies, typically ranging from 6-15 hours, depending on the individual and specific formulation. Promethazine crosses the blood-brain barrier and placental barrier. |
| suggested dosage | Dosage varies greatly depending on the specific indication (e.g., allergy, nausea, cough). Consult with a healthcare professional for appropriate dosage in a male patient aged 25 with a weight of 70 kg. Dosage should be tailored to individual needs and monitored closely by a doctor. |
| indications | | 1 | Allergic rhinitis | | 2 | Urticaria | | 3 | Motion sickness | | 4 | Nausea and vomiting | | 5 | Postoperative nausea and vomiting | | 6 | Cough | | 7 | Mild to moderate pain |
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| Safety in pregnancy | Promethazine crosses the placenta. It is categorized as a Pregnancy Category B in the US, meaning animal studies have not shown a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women. However, due to potential risks, it's best avoided in pregnancy, especially during the first trimester, unless the benefit outweighs the risk, under direct medical supervision. |
| Safety in breastfeeding | Promethazine is excreted in breast milk. Due to potential side effects in the infant, the use of Promethazine during breastfeeding is generally not recommended, unless the potential benefit for the mother outweighs the potential risk to the infant, under direct medical supervision. |
| side effects | | 1 | Sedation | | 2 | Drowsiness | | 3 | Dry mouth | | 4 | Constipation | | 5 | Blurred vision | | 6 | Urinary retention | | 7 | Orthostatic hypotension | | 8 | Cardiac arrhythmias (rare) | | 9 | Confusion | | 10 | Hallucinations (rare) | | 11 | Photosensitivity | | 12 | Skin rash |
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| alternatives | |
| contraindications | | 1 | Known hypersensitivity to promethazine or related compounds | | 2 | Severe hepatic impairment | | 3 | Narrow-angle glaucoma | | 4 | Prostatic hypertrophy | | 5 | Respiratory depression | | 6 | Patients with a history of significant cardiac arrhythmias or other cardiovascular disease |
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| interactions | Promethazine may interact with several medications, including CNS depressants (e.g., alcohol, opioids), anticholinergics, and certain drugs metabolized by CYP2D6. Consult a doctor about any medications the patient is currently taking. |
| warnings and precautions | | 1 | Use caution in patients with a history of seizures or epilepsy. | | 2 | Use caution in patients with pre-existing respiratory issues. | | 3 | Avoid driving or operating machinery while taking promethazine due to drowsiness. | | 4 | Monitor for signs of paradoxical reactions (e.g., agitation or excitation), especially in children. | | 5 | Long-term use should be avoided unless under close medical supervision. |
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| additional information | | 1 | Available in various formulations (e.g., oral tablets, syrup, injections). | | 2 | Overdose can lead to serious complications; seek immediate medical attention if an overdose is suspected. |
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