Rhadbdomyolysis after coronary artery bypass grafting in a patient receiving simvastatin

Low Myopathy Rates Associated with Statins as Monotherapy or Combination Therapy with Interacting Drugs in a Group Model Health Maintenance Organization

STUDY OBJECTIVE

Because the risk for myopathy increases when 3-hydroxy-3-methylglutaryl coenzyme A inhibitors (statins) are used with other agents known to inhibit cytochrome P450 3A4 in patients with dyslipidemia, we sought to quantify this risk in a diverse, real-world sample of patients receiving statin therapy.

DESIGN

Retrospective chart review.

SETTING

Kaiser Permanente Colorado (KPCO), a group model health maintenance organization with approximately 360,000 members.

PATIENTS

Four hundred sixty-eight patients who were identified as having a diagnosis of myopathy over a 4-year period using KPCO computerized data systems.

MEASUREMENTS AND MAIN RESULTS

Medical records were reviewed to confirm myopathy cases associated with statin therapy. Of the 468 patients, 61 had received statin therapy before their diagnosis, and 41 (67%) of these patients had confirmed myopathy (documented creatine kinase level>or=1000 IU/L). The prevalence of myopathy was 0.12% with statin monotherapy and 0.22% with statins in combination with interacting drugs. Only 17 of the 41 (41%) patients had confirmed myopathy with no other plausible clinical explanation, such as a muscle injury. Increased risk of myopathy associated with statin therapy in combination with interacting drugs approached statistical significance (p=0.052) but was of minimal clinical significance.

CONCLUSION

The prevalence of confirmed myopathy in patients receiving statin therapy is low (<1%). Combining statin therapy with interacting drugs (e.g., fibrates) was not associated with a clinically important increase in the prevalence of myopathy. The risk of developing myopathy during statin therapy is outweighed by the benefits derived from the therapeutic effects of the therapy.

Drug-induced myopathy and neuropathy

We review the drugs that are known to induce muscle and/or nerve toxicity, describe the commonly encountered signs and symptoms, and discuss the mechanisms believed to be behind these iatrogenic effects. The diagnostic approach to patients suspected of having drug-induced neuromuscular disorders includes a comprehensive history and physical examination, proper blood workup, electrophysiological studies, and, if necessary, muscle or nerve biopsy. A lot of controversial issues continue to prevail when reviewing such a topic, secondary to the greatly variable levels of certainty for the association between drugs and their neuromuscular toxicity. We focus on drugs that are proven to cause these adverse effects, with less emphasis on the anecdotally suspected agents for which coincidence has not been eliminated.

Malignant hyperthermia and myotonic disorders

Advances in physiology and molecular genetics have promoted greater understanding of the various clinical manifestations of muscle disorders. For example, myotonia or profound weakness may be observed in sodium channel disease (e.g., paramyotonia congenita or hyperkalemic periodic paralysis), depending on the specific channel defect or with slight changes in membrane potential. Observed effects of anesthetic techniques have been essential to elucidating the primary muscular nature of myotonia. Commonly used anesthetic medications have potentially lethal (e.g., MH) or serious (e.g., myotonic dystrophy) adverse effects. Conversely, lidocaine or propofol may have therapeutic benefit for patients with skeletal muscle sodium channel disorders. Additional investigation is required to improve our understanding of how age, gender, or other factors determine the phenotypic expression of malignant hyperthermia. Future research holds the promise for more accurate pre-anesthetic identification of persons with heritable myopathies, especially those who are asymptomatic. Enhanced awareness of multiple organ system involvement in myotonic dystrophy is essential for planning perioperative care. Patients with periodic paralysis require that we know factors that incite or inhibit the development of their attacks. Advances in bench research and detailed clinical studies will further improve our ability to provide optimal care for patients with muscle disorders.

Rhabdomyolysis and HMG-CoA reductase inhibitors

OBJECTIVE

To review rhabdomyolysis and discuss the role of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) and their interactions with other agents in precipitating this condition, and to present case reports of statin-induced rhabdomyolysis.

DATA SOURCE

Relevant clinical literature was accessed using MEDLINE (January 1985-October 2000). The following search terms were used: rhabdomyolysis, adverse events, drug interactions, statins, and HMG-CoA reductase inhibitors.

DISCUSSION

Rhabdomyolysis occurs when extensive muscle damage results in the release of cellular contents into systemic circulation. Major complications include acute renal failure, cardiac abnormalities, and compartment syndrome. Treatment of rhabdomyolysis is supportive, with the primary aim of preventing renal and cardiac complications. Statin monotherapy or combination therapy may result in myopathy, which rarely progresses to rhabdomyolysis. The mechanism for drug interactions with the statins involves their property of lipid or water solubility. This characteristic determines the degree of hepatoenteric or renal metabolism of the statins. All statins except pravastatin undergo metabolism via the cytochrome P450 enzyme system. Other pharmacologic agents that are also metabolized via this pathway may interact with the statins and cause rhabdomyolysis. The risk of statin-induced rhabdomyolysis is increased significantly when statins are used concomitantly with such drugs as fibrates, cyclosporine, macrolide antibiotics, and azole antifungals.

CONCLUSIONS

Rhabdomyolysis is a rare but clinically important adverse event of statin monotherapy or combination therapy. Thorough understanding of this condition may help prevent or minimize adverse health outcomes in patents receiving statin therapy.

The effects of toxins on muscle

Substances known to be myotoxic are reviewed, including descriptions of the resultant clinical syndromes and the mechanisms important in their development. Certain host characteristics such as altered immune and metabolic regulation are known to modulate the effects of individual myotoxins, producing varied clinical syndromes. Evaluation procedures important in identifying a toxin-induced myopathy are described.

Low-density lipoprotein-independent effects of statins

Statins have pleiotropic properties that complement their cholesterol-lowering effects. These properties may partly account for their established benefit in the prevention of coronary artery disease beyond the reduction of LDL-cholesterol levels. The most widely recognized properties are reviewed here. They include: (i) nitric oxide-mediated improvement of endothelial dysfunction and upregulation of endothelin-1 expression; (ii) antioxidant effects; (iii) anti-inflammatory properties; (iv) inhibition of cell proliferation with anticarcinogenic actions in animals; (v) stabilization of atherosclerotic plaques; (vi) anticoagulant effects; and (vii) inhibition of graft rejection after heart and kidney transplantation. As advances are made in our knowledge, new properties are steadily being uncovered. Pleiotropic effects are currently being given consideration when instituting combination therapy for patients at high cardiovascular risk. Some pleiotropic effects are negative, and may account for occasional untoward drug interactions. For many of these new properties, the clinical relevance has not been established. The challenge for the future will be to design and carry out appropriate clinical trials to establish their relative importance in the prevention of coronary artery disease.