Drug interactions between Mellaril and Seroquel
| Results for the following 2 drugs: |
|---|
| Mellaril (thioridazine) |
| Seroquel (quetiapine) |
Interactions between your selected drugs
thioridazine ↔ quetiapine
Applies to:Mellaril (thioridazine) and Seroquel (quetiapine)
CONTRAINDICATED: Thioridazine can cause dose-related prolongation of the QT interval. Theoretically, coadministration with other agents that can prolong the QT interval including other antipsychotic agents may result in additive effects and increased risk of ventricular arrhythmias. Thioridazine treatment alone has been associated with several reported cases of torsade de pointes and sudden death.
Coadministration with thioridazine may decrease the plasma concentrations of quetiapine. The mechanism of interaction is unknown. In one study, thioridazine (200 mg twice a day for 8.5 days) administered to patients stabilized on quetiapine (300 mg twice a day) resulted in decreases in mean quetiapine peak plasma concentration (Cmax), systemic exposure (AUC) and trough plasma concentration (Cmin) by 47%, 40% and 31%, respectively. Quetiapine oral clearance (Cl/F) increased by 68%. Patients in the study reported increases in dizziness, insomnia, and dry mouth during coadministration, while sedation and prolonged sleep duration became worse in more than 25% of the patients. This is consistent with additive anticholinergic and CNS-depressant effects of these agents. Excessive anticholinergic effects can also result in paralytic ileus, hyperthermia, heat stroke, and the anticholinergic intoxication syndrome. Peripheral symptoms of anticholinergic intoxication commonly include mydriasis, blurred vision, flushed face, fever, dry skin and mucous membranes, tachycardia, urinary retention, and constipation. Central symptoms may include memory loss, disorientation, incoherence, hallucinations, psychosis, delirium, hyperactivity, twitching or jerking movements, stereotypy, and seizures. Other adverse effects that may be increased with this combination include orthostatic hypotension, extrapyramidal symptoms, and tardive dyskinesia.
MANAGEMENT: The concurrent use of thioridazine with other medications that can prolong the QT interval is considered contraindicated.
See also...
Drug Interaction Classification
The classifications below are a guideline only. The relevance of a particular drug interaction to a specific patient is difficult to determine using this tool alone given the large number of variables that may apply.
| Major | Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. |
| Moderate | Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. |
| Minor | Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. |
Do not stop taking any medications without consulting your healthcare provider.
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