Can olmesartan (angiotensin II receptor antagonist) cause myositis?

Olmesartan and Myositis: Association and Risk Assessment

Based on the available evidence, olmesartan is not known to cause myositis as an adverse effect. There is no documented association between olmesartan (an angiotensin II receptor antagonist) and the development of inflammatory muscle disease in the current medical literature.

Understanding Myositis

Myositis is characterized by:

• Muscle weakness (primarily in proximal extremities)
• Elevated muscle enzymes (particularly creatine kinase/CK)
• Inflammatory changes on diagnostic testing
• Potential myalgia (muscle pain) in severe cases 1

Known Causes of Myositis

The primary documented causes of drug-induced myositis include:

1. Immune checkpoint inhibitors (ICPis): Particularly PD-1/PD-L1 inhibitors, which are more commonly associated with myositis than CTLA-4 inhibitors 2
2. Statins: Well-established cause of myopathy and myositis
3. Other medications: Not including angiotensin II receptor antagonists like olmesartan

Olmesartan's Known Adverse Effects

Olmesartan has been associated with:

• Enteropathy with gastrointestinal symptoms 3
• Angioedema (rare) 4
• Beneficial effects in experimental autoimmune myocarditis models 5, 6, 7

Diagnostic Approach for Suspected Myositis

If a patient on olmesartan presents with muscle symptoms:

1. Differentiate between myalgia and myositis:

   • Myalgia: Pain without weakness, normal CK
   • Myositis: Weakness with or without pain, elevated CK

2. Laboratory evaluation:

   • Muscle enzymes (CK, AST, ALT, LDH, aldolase)
   • Inflammatory markers (ESR, CRP)
   • Consider myositis-specific antibodies

3. Consider other causes:

   • Other medications (particularly statins)
   • Autoimmune conditions
   • Viral infections
   • Malignancy

Management Considerations

If a patient on olmesartan develops confirmed myositis:

• The myositis is likely due to another cause rather than olmesartan
• Consider other medications the patient may be taking
• Evaluate for underlying autoimmune conditions or malignancy
• Treatment should follow standard myositis protocols with corticosteroids and potentially other immunosuppressants 1

Clinical Implications

• Olmesartan can be continued in patients who develop myositis, as there is no evidence linking it to muscle inflammation
• Focus diagnostic efforts on identifying other potential causes of myositis
• Consider the possibility that the patient may have been prescribed a statin concurrently for cardiovascular risk reduction, which is a more likely cause of myositis

In conclusion, when evaluating a patient on olmesartan with muscle symptoms, clinicians should consider other etiologies for myositis rather than attributing it to olmesartan therapy.