Drug interactions
Lamivudine + Trimethoprim
Severity: Minor
Lamivudine and Trimethoprim: minor 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
Trimethoprim, usually given as co-trimoxazole, raises lamivudine exposure by roughly a third in studies. The increase is generally modest and not clinically important when renal function is normal.
What this interaction means in plain words
Lamivudine and Trimethoprim have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Lamivudine belongs to Anti Virals; Trimethoprim belongs to Anti Bacterial.
Why it happens
Trimethoprim competes with lamivudine for renal tubular cationic secretion (OCT2/MATE), reducing lamivudine renal clearance.
What to do
No dose change is needed with normal renal function, including standard-dose co-trimoxazole. Consider reviewing lamivudine dosing if high-dose trimethoprim is used or the patient has renal impairment.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Lamivudine
Other interactions of Trimethoprim
Frequently asked questions
Can I take Lamivudine with Trimethoprim?
MediHelp rates the interaction as minor. Lamivudine and Trimethoprim have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Trimethoprim, usually given as co-trimoxazole, raises lamivudine exposure by roughly a third in studies. The increase is generally modest and not clinically important when renal function is normal.
How serious is the interaction between Lamivudine and Trimethoprim?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No dose change is needed with normal renal function, including standard-dose co-trimoxazole. Consider reviewing lamivudine dosing if high-dose trimethoprim is used or the patient has renal impairment.
What other medicines interact with Lamivudine?
MediHelp also lists interactions of Lamivudine with, for example, Elvitegravir / cobicistat / emtricitabine / tenofovir df, Atidarsagene autotemcel, Betibeglogene autotemcel. The full list is on the Lamivudine page.
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