Clinical pharmacology of promethazine/ dextromethorphan:
Promethazine is an H1 receptor blocking agent that provides an antihistaminic effect. Promethazine blocks mesolimbic dopamine receptors and alpha-adrenergic receptors in the brain. It gives 25% bioavailability and has a duration time of 4-6 hours with an onset duration of 20 mins. It has a 93% protein binding ratio. Promethazine metabolizes in the liver and excreted from urine and feces. Dextromethorphan is derivative of levorphanol and acts on the cough center in medulla with an onset period of 15-30 min and has a duration of action of 3 to 6 hours along with peak plasma time of 2 to 3 hours. Its half-life is about 24 hr with poor metabolizer and 2 to 4 hr with extensive metabolizer.
Dosage and administration:
Promethazine/dextromethorphan (6.25mg/ 15mg) 5 mL administered orally. The maximum dose for 24 hr is 30ml. Read more
|Children age 2 years to 6 years.||1/4 to 1/2 teaspoonful (1.5 ml to 2.5 ) every 4 to 6 hours.
Not to exceed 10 ml in 24 hours.
|Children of age 6 years to 12 years||1/2 to 1 teaspoonful (2.5 ml to 5 ml) every 4 to 6 hours.
Not to exceed 20 ml in 24 hours.
|Adults||1 teaspoonful (5ml) every 4 to 6 hours.
Not to exceed 30 ml in 24 hours.
|Children less than 2 years||Contraindicated
- Promethazine DM syrup is prescribed in case of following diseases or purposes.
- Allergic rhinitis (runny nose and watery eyes)
- Allergic conjunctivitis (redness of eyes)
- Rashes on skin or hives.
- Allergic reactions to blood or plasma.
- It can also be used in combination with epinephrine to treat severe allergic reactions(anaphylaxis).
- Promethazine is also used for sedation and to prevent motion sickness disease.
- It is also used to prevent nausea, vomiting, and linked with anesthesia.
- It is also used intravenously for special surgical situations.
- It can also be prescribed to pregnant women because a controlled study proved it does not harm fetal.
- Promethazine should not be used in patients receiving MAO inhibitor.
- Contraindicated for treatment of lower respiratory tract syndrome e.g asthma.
- It is also contraindicated for hypersensitive persons.
- Contraindicated through subcutaneous or intraarterial administration.
- Contraindicated for patients of narrow-angle glaucoma.
- Should not be prescribed to patients of severe CNS depression.
- It can cause cardiovascular disease and also contraindicated for bone marrow disease or lung diseases.
Dry mouth, drowsiness, nausea, vomiting, constipation, blurred vision may occur. To minimize dizziness get up slowly while sitting or lying down. If you feel uncomfortable walking or felt sleepy stop using this medication. Nightmare is a common side effect of promethazine. Sometimes it may cause hallucination (hearing of voices that do not exist in reality or seeing such things that do not exist in real life.) it cause uncontrolled eye movement. It can also cause confusion to the patient. Side effects of promethazine include unusual bruising or bleeding. It may cause unmanageable fear or emotion and sometimes slower the heartbeat.