How the interaction occurs:
When these two medicines are taken together, your body may process the medicines differently.
What might happen:
The effects of your barbiturate may increase and cause increased drowsiness, slowed breathing, and a decrease in blood pressure. The effects of your phenothiazine may decrease and it may not work as well.
What you should do about this interaction:
If you experience excessive drowsiness, slowed breathing, weakness, fatigue, or dizziness, contact your doctor. It may be necessary to monitor your blood pressure and breathing rate. Let your doctor know if your symptoms worsen. Your doctor may need to adjust the dose of your medicines.Your healthcare professionals (e.g. doctor or pharmacist) may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Phenergan (promethazine hydrochloride) US prescribing information. Baxter Healthcare Corporation December, 2006.
2.Chlorpromazine hydrochloride US prescribing information. Baxter Healthcare Corporation October, 2006.
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