Drug interactions
Methamphetamine + Thioridazine
Severity: Major
Methamphetamine and Thioridazine: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Thioridazine strongly prolongs the QT interval and inhibits CYP2D6, which can raise methamphetamine levels. Stimulant-induced tachycardia and sympathetic activation add to the risk of torsades de pointes and sudden cardiac death.
What this interaction means in plain words
Methamphetamine and Thioridazine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Methamphetamine belongs to Central Nervous System; Thioridazine belongs to Central Nervous System.
Why it happens
CYP2D6 inhibition by thioridazine, additive cardiac effects including QT prolongation, and opposing dopaminergic actions.
What to do
Avoid the combination if possible and choose a lower-risk antipsychotic. If unavoidable, monitor ECG and electrolytes and watch for syncope or palpitations.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Methamphetamine
- Isocarboxazid + Methamphetamine Contraindicated
- Linezolid + Methamphetamine Contraindicated
- Methamphetamine + Phenelzine Contraindicated
- Methamphetamine + Procarbazine Contraindicated
- Methamphetamine + Rasagiline Contraindicated
- Methamphetamine + Safinamide Contraindicated
Other interactions of Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Frequently asked questions
Can I take Methamphetamine with Thioridazine?
MediHelp rates the interaction as major. Methamphetamine and Thioridazine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Thioridazine strongly prolongs the QT interval and inhibits CYP2D6, which can raise methamphetamine levels. Stimulant-induced tachycardia and sympathetic activation add to the risk of torsades de pointes and sudden cardiac death.
How serious is the interaction between Methamphetamine and Thioridazine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination if possible and choose a lower-risk antipsychotic. If unavoidable, monitor ECG and electrolytes and watch for syncope or palpitations.
What other medicines interact with Methamphetamine?
MediHelp also lists interactions of Methamphetamine with, for example, Isocarboxazid, Linezolid, Phenelzine. The full list is on the Methamphetamine page.
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