Drug interactions
Lithium + Promethazine
Severity: Moderate
Lithium and Promethazine: moderate 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
Phenothiazines combined with lithium have been associated with neurotoxicity, including confusion, tremor and extrapyramidal signs, and in rare cases encephalopathy. Promethazine can also mask early features of lithium toxicity such as nausea and vomiting because of its antiemetic action.
What this interaction means in plain words
Lithium and Promethazine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Lithium belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive central neurotoxicity and dopamine blockade; antiemetic effect may mask lithium toxicity symptoms.
What to do
Monitor for neurological symptoms and check serum lithium levels if toxicity is suspected. Do not rely on absence of nausea to exclude lithium toxicity.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Other interactions of Lithium
- Lithium + Thioridazine Contraindicated
- Lithium + Vandetanib Contraindicated
- Aceclofenac + Lithium Major
- Acemetacin + Lithium Major
- Amisulpride + Lithium Major
- Amlodipine-benazepril + Lithium Major
Frequently asked questions
Can I take Lithium with Promethazine?
MediHelp rates the interaction as moderate. Lithium and Promethazine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenothiazines combined with lithium have been associated with neurotoxicity, including confusion, tremor and extrapyramidal signs, and in rare cases encephalopathy. Promethazine can also mask early features of lithium toxicity such as nausea and vomiting because of its antiemetic action.
How serious is the interaction between Lithium and Promethazine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for neurological symptoms and check serum lithium levels if toxicity is suspected. Do not rely on absence of nausea to exclude lithium toxicity.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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