Interactions : אינטראקציות

4.5 Interaction with other medicinal products and other forms of interaction
Phenergan will enhance the action of any anticholinergic agent, tricyclic anti- depressant, sedative or hypnotic.

Alcohol should be avoided during treatment. Combination with alcohol enhances the sedative effects of H1 antihistamines.

Phenergan may cause hypotension, and dosage adjustment of antihypertensive therapy may therefore be required.
Phenergan may lower the convulsive threshold, and dosage adjustment of anticonvulsant medication may therefore be required.

Phenergan may interfere with immunological urine pregnancy tests to produce false-positive or false-negative results.

Phenergan should be discontinued at least 72 hours before the start of skin tests as it may inhibit the cutaneous histamine response thus producing false- negative results.


Special caution is required when promethazine is used concurrently with drugs known to cause QT prolongation (such as antiarrhythmics, antimicrobials, antidepressants, antipsychotics) to avoid exacerbation of risk of QT prolongation.

Cytochrome P450 2D6 Metabolism: Some phenothiazines are moderate inhibitors of CYP2D6. There is a possible pharmacokinetic interaction between inhibitors of CYP2D6, such as phenothiazines, and CYP2D6 substrates. Co administration of promethazine with amitriptyline/amitriptylinoxide, a CYP2D6 substrate, may lead to an increase in the plasma levels of amitriptyline/amitriptylinoxide. Monitor patients for dose-dependent adverse reactions associated with amitriptyline/amitriptylinoxide.

Phenergan should be avoided in patients taking monoamine oxidase inhibitors within the previous 14 days, and monoamine oxidase inhibitors should be avoided while using Phenergan.

Seizure threshold-lowering drugs: Concomitant use of seizure-inducing drugs or seizure threshold-lowering drugs should be carefully considered due to the severity of the risk for the patient (see section 4.4).

Gastro-intestinal agents that are not absorbed (magnesium, aluminium and calcium salts, oxides and hydroxides): Reduced gastro-intestinal absorption of phenothiazines may occur. Such gastro-intestinal agents should not be taken at the same time as phenothiazines (at least 2 hours apart, if possible).

Drugs with anticholinergic properties: Concomitant use of Phenergan with drugs with anticholinergic properties enhances the anticholinergic effect.