Losartan Does Not Cause False-Positive Drug Tests
Losartan, an angiotensin II receptor blocker (ARB), is not associated with false-positive results on standard urine drug screens. This is based on the available evidence regarding medications that cross-react with immunoassay drug testing panels.
Evidence on False-Positive Drug Screens
The most comprehensive guideline on drug testing in clinical practice discusses false-positive results extensively but does not identify losartan or any ARBs as causative agents 1. The American Academy of Pediatrics guidelines specifically note that:
- False-positive results occur due to cross-reactivity with immunoassay screening tests 1
- Examples of medications causing false-positives include fluoroquinolone antibiotics (cross-reacting with opiate screens) 1
- Prescription medications like amphetamine/dextroamphetamine for ADHD will test positive for amphetamines, but this represents appropriate medication use rather than a true false-positive 1
Medications That DO Cause False-Positives
A systematic review of commonly prescribed medications identified specific agents associated with false-positive urine drug screens, including antihistamines (brompheniramine, diphenhydramine), antidepressants (bupropion, sertraline, trazodone, venlafaxine), antibiotics (quinolones like ofloxacin and gatifloxacin), analgesics (ibuprofen, naproxen), antipsychotics (quetiapine, chlorpromazine), and other agents like ranitidine and verapamil 2. Notably, losartan and other ARBs are absent from this comprehensive list 2.
Clinical Implications for Losartan Use
Losartan is extensively studied and well-characterized pharmacologically:
- Losartan is metabolized primarily by CYP3A4, 2C9, and 2C10 isoenzymes to its active metabolite E-3174 3
- The drug has a favorable drug-drug interaction profile with no clinically relevant interactions with most medications 3
- Losartan is well-tolerated with dizziness being the only drug-related adverse effect reported more frequently than placebo 4, 5
Practical Guidance
If a patient taking losartan has a positive drug screen:
- The positive result is NOT attributable to losartan 2
- Investigate other medications, supplements, or substances the patient may be taking 1, 2
- Consider confirmatory testing with gas chromatography-mass spectrometry to identify the true causative substance 1, 2
- Review the patient's complete medication list, including over-the-counter medications and herbal supplements 1
Common pitfall to avoid: Do not assume that all prescription medications can cause false-positive drug screens. Only specific classes of medications have documented cross-reactivity with immunoassay testing 2.