Statin-Induced Myopathy

Pathophysiology

Overview

Statin-induced myopathy encompasses a spectrum from mild myalgia to severe rhabdomyolysis, caused by HMG-CoA reductase inhibitor medications. Symptoms typically begin within weeks to months of starting or increasing statin dose and resolve with dose reduction or cessation.

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Medically Managed — Refer Early

This condition is primarily medically managed. Osteopathic care may play a supportive role — refer early if suspected.

Typical Presentation

Site

Proximal limb muscles, bilateral and symmetrical; thighs and calves common

Quality

Aching, cramping, heaviness; weakness in severe cases

Intensity

Variable; mild myalgia to severe weakness depending on spectrum

Aggravating

Exercise, recent dose increase, concurrent use of CYP3A4 inhibitors

Relieving

Dose reduction or cessation of statin (under GP guidance)

Associated

Medication history of statin use; symptoms may follow dose change

⚠ Red Flags

  • •Dark urine or markedly elevated CK (>10x upper limit of normal) suggesting rhabdomyolysis — emergency referral
  • •Rapid progressive weakness suggesting immune-mediated necrotising myopathy (IMNM)
  • •Symptoms persisting after statin cessation suggesting IMNM

⚡ Yellow Flags

  • •Patient self-managing by stopping statins without GP involvement
  • •Statin non-adherence due to myalgia without discussing alternatives with GP

Referral Criteria

  • •GP referral for CK testing and medication review — statin dose reduction or substitution
  • •Emergency referral if rhabdomyolysis suspected
  • •Rheumatology if IMNM suspected (weakness persisting after cessation)