Phez Drug Interactions

Concomitant administration of Phenylephrine with cycloplegic antimuscarinic drugs such as atropine sulfate, cyclopentolate hydrochloride, homatropine hydrobromide, or scopolamine hydrobromide produces increased dilation of the pupil which is of clinical value.
Phenylephrine must be administered under careful supervision and in reduced dosage if used within 21 days after the patient has received a monoamine oxidase inhibitor (MAOI) because potentiation of the pressor effects of phenylephrine may result. There is an increased risk of hypertension when used concurrently with the administration of MAOIs.
The pressor response to Phenylephrine may be potentiated if a tricyclic antidepressant is administered concomitantly. The risk of raised blood pressure and cardiac arrhythmia may also be potentiated.
If Phenylephrine is administered to a patient undergoing chronic oral therapy with guanethidine, the pupillary response to Phenylephrine is greatly increased and the pressor response may also be potentiated. There is an increased risk of hypertension when used concurrently with the administration of guanethidine. Phenylephrine should be administered cautiously to patients receiving guanethidine.
The mydriatic response to Phenylephrine is decreased in patients receiving levodopa.
Because of the increased risk of cardiovascular effects, Phenylephrine should be used with caution during general anaesthesia with anaesthetic agents.