Can Olmesartan Cause Leukopenia?
No, olmesartan does not cause leukopenia, but it is well-documented to cause a severe sprue-like enteropathy with villous atrophy that can mimic celiac disease. This is a critical adverse effect that clinicians must recognize, as it can lead to severe chronic diarrhea, weight loss, and malabsorption requiring drug discontinuation.
The Established Adverse Effect: Olmesartan-Induced Enteropathy
Olmesartan is specifically listed as a medication that causes seronegative enteropathy with villous atrophy, not leukopenia. 1 This enteropathy presents with:
- Severe chronic diarrhea and substantial weight loss
- Duodenal villous atrophy on biopsy that mimics celiac disease
- Negative celiac serologies (tissue transglutaminase antibodies, endomysial antibodies)
- Resolution of symptoms after olmesartan discontinuation 1
The British Society of Gastroenterology explicitly includes olmesartan in their differential diagnosis table for histological mimics of celiac disease in seronegative patients, categorizing it under "Drugs" as a cause of villous atrophy. 1 The American Gastroenterological Association similarly emphasizes that clinicians should obtain a thorough medication history to determine whether a patient is taking olmesartan when evaluating seronegative enteropathy. 1
Hematologic Effects: What Actually Occurs
There is no evidence in the provided guidelines or research that olmesartan causes leukopenia. The documented adverse effects of olmesartan include:
- Hyperkalemia (9.2% incidence in clinical trials), which is more frequent than placebo (5.3%) 2
- Standard angiotensin receptor blocker side effects such as hypotension and renal dysfunction 1
- Photosensitivity reactions (olmesartan is listed among ARBs that can cause drug-induced photosensitivity) 1
Clinical Implications for Cardiovascular Patients
For patients with cardiovascular disease taking olmesartan, the primary concerns are:
- Cardiovascular safety: One study showed an unexpected higher rate of fatal cardiovascular events with olmesartan compared to placebo among patients with pre-existing cardiovascular disease, though this finding requires careful interpretation in context. 1
- Renal monitoring: When olmesartan is used, serum creatinine and potassium levels must be monitored for hyperkalemia and changes in renal function. 1
- Enteropathy surveillance: Patients developing unexplained chronic diarrhea, weight loss, or malabsorption symptoms should have olmesartan discontinued and undergo evaluation for drug-induced enteropathy. 1
What to Monitor Instead of Leukopenia
The critical monitoring parameters for olmesartan are:
- Serum potassium levels (risk of hyperkalemia, especially when combined with other RAAS inhibitors) 1, 2
- Renal function (serum creatinine, eGFR) 1
- Gastrointestinal symptoms (chronic diarrhea, weight loss suggesting enteropathy) 1
- Blood pressure response and cardiovascular outcomes 2
There is no indication to monitor white blood cell counts specifically for olmesartan therapy based on the available evidence, as leukopenia is not a recognized adverse effect of this medication.