Phenylephrineinteractions

Promethazine CNS Depressants Promethazine may increase, prolong, or intensify the sedative action of other central nervous system depressants, such as alcohol, sedatives/hypnotics (including barbiturates), narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and tranquilizers; therefore, such agents should be avoided or administered in reduced dosage to patients receiving promethazine HCl. When given concomitantly with promethazine, the dose of barbiturates should be reduced by at least one-half, and the dose of narcotics should be reduced by one-quarter to one-half. Dosage must be individualized. Excessive amounts of promethazine HCl relative to a narcotic may lead to restlessness and motor hyperactivity in the patient with pain; these symptoms usually disappear with adequate control of the pain. Epinephrine Because of the potential for promethazine to reverse epinephrine's vasopressor effect, epinephrine should NOT be used to treat hypotension associated with promethazine overdose. Anticholinergics Concomitant use of other agents with anticholinergic properties should be undertaken with caution. Monoamine Oxidase Inhibitors (MAOI) Drug interactions, including an increased incidence of extrapyramidal effects, have been reported when some MAOI and phenothiazines are used concomitantly. Phenylephrine Drug Phenylephrine with prior administration of monoamine oxidase inhibitors (MAOI). Effect Cardiac pressor response potentiated. May cause acute hypertensive crisis. Drug Phenylephrine with tricyclic antidepressants. Effect Pressor response increased. Drug Phenylephrine with ergot alkaloids. Effect Excessive rise in blood pressure. Drug Phenylephrine with bronchodilator sympathomimetic agents and with epinephrine or other sympathomimetics. Effect Tachycardia or other arrhythmias may occur. Drug Phenylephrine with atropine sulfate. Effect Reflex bradycardia blocked; pressor response enhanced. Drug Phenylephrine with prior administration of propranolol or other β-adrenergic blockers. Effect Cardiostimulating effects blocked. Drug Phenylephrine with prior administration of phentolamine or other α-adrenergic blockers. Effect Pressor response decreased. Drug Phenylephrine with diet preparations, such as amphetamines or phenylpropanolamine. Effect Synergistic adrenergic response.