Drug Interactions between Benylin Multi-Symptom and thioridazine

Using thioridazine together with diphenhydrAMINE is not recommended. Combining these medications may increase the blood levels of thioridazine to dangerous levels and cause an irregular heart rhythm that may be serious and potentially life-threatening. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment with thioridazine. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

GENERALLY AVOID: Phenothiazines may antagonize the pharmacologic effects of amphetamine, amphetamine derivatives, and other centrally-acting sympathomimetic agents (i.e., CNS stimulants). Conversely, these agents may diminish the neuroleptic efficacy of phenothiazines. The exact mechanism of interaction is unknown but may involve opposing effects on dopaminergic activity. Several clinical studies have demonstrated the reduction or lack of effect of amphetamines on weight loss in obese psychiatric patients treated with chlorpromazine and other neuroleptic agents. In one of these studies, dextroamphetamine also had no effect on sleep patterns. As for the reverse interaction, it is uncertain whether CNS stimulants actually antagonize the neuroleptic effect of phenothiazines, since CNS stimulants alone have been reported to cause or aggravate preexisting psychotic symptoms. Finally, it is conceivable that, because of their sympathomimetic effects, CNS stimulants may also potentiate the arrhythmogenicity of phenothiazines. A case of fatal ventricular arrhythmia was reported in a patient treated chronically with thioridazine who ingested a single capsule containing phenylpropanolamine 50 mg and chlorpheniramine 4 mg. However, a causal relationship was not established.

MANAGEMENT: Amphetamine, amphetamine derivatives, and other CNS stimulants should generally not be used, particularly for weight reduction, in patients treated with phenothiazines.