The role of cytochrome P450-mediated drug-drug interactions in determining the safety of statins

The objectives of this review are to discuss the role of cytochrome P450 (CYP450) isoforms in drug metabolism, to explain differences in metabolism among the HMG-CoA reductase inhibitors (HMGs, statins), to review drug-drug and drug-food interaction studies dealing with the HMGs, to present case reports dealing with HMG-related myopathy, to discuss major clinical implications of these case reports and to express an opinion of use of HMGs in clinical practice.     

Potential role of coenzyme Q10 in facilitating recovery from statin‐induced rhabdomyolysis

Rhabdomyolysis is a rare, but serious complication of statin therapy, and represents the most severe end of the spectrum of statin‐induced myotoxicity. We report a case where coenzyme Q10 facilitated recovery from statin‐induced rhabdomyolysis and acute renal failure, which had initially persisted despite statin cessation and haemodialysis. This observation is biologically plausible due to the recognised importance of coenzyme Q10 in mitochondrial bioenergetics within myocytes, and the fact that statins inhibit farnesyl pyrophosphate production, a biochemical step crucial for coenzyme Q10 synthesis. Coenzyme Q10 is generally well tolerated, and may potentially benefit patients with statin‐induced rhabdomyolysis.     

Status spasticus and psoas muscle edema due to anti-GAD antibody associated stiff-man syndrome

Severe muscle rigidity and spasms are uncommon causes of Intensive Care Unit (ICU) admissions. Stiff-man syndrome (SMS) is a rare disorder characterized by continuous muscle spasms, axial muscle rigidity, “tin soldier gait,” and continuous motor unit activity on electromyography. There are three clinical variants of SMS; stiff-limb syndrome, classical SMS, and paraneoplastic encephalomyelitis with rigidity and myoclonus. Three types of antibodies have been associated with SMS; however, anti-glutamic acid decarboxylase (GAD) antibodies are the most frequent and are seen in the idiopathic type of SMS. The spasms of SMS can be very disabling and severe enough to cause muscle ruptures and skeletal fractures. We present a case of anti-GAD positive SMS with “status spasticus” causing bilateral psoas myoedema and rhabdomyolysis due to repeated axial muscle jerking in a 64-year-old man and discuss the differential diagnosis of a “jerking patient in the ICU.”     

An inherited disorder characterized by repeated episodes of bilateral ballism: a case report.

This case report describes two siblings with a dyskinetic form of cerebral palsy who had repeated episodes of fever-induced bilateral ballistic movements. The boy and his sister experienced the first episodes during early childhood. The movements developed over several hours and required rapid intervention. Electroencephalograms during the attacks showed no paroxysms, and brain magnetic resonance imaging scans revealed no lesions. The brother died of acute renal failure at age 5 due to rhabdomyolysis after his fifth episode of prolonged bilateral ballistic movements. This is the first report of an inherited disorder characterized by repeated episodes of violent movements.     

Myoglobinuria masquerading as acute rejection in a renal allograft recipient with recurrent post transplant diabetic nephropathy

Rhabdomyolysis contributes to 7–10% of total AKI cases. Myoglobinuria as a cause of acute renal allograft dysfunction is extremely uncommon. Renal allograft recipient on cyclosporine or tacrolimus can develop myoglobinuria in presence of other precipitating factors. Present case describes an interesting report of myoglobinuria in a patient with post transplant diabetic nephropathy mimicking acute graft rejection. Clinically myoglobinuria presenting as renal allograft dysfunction is diagnosis of exclusion and renal biopsy is extremely important in making a correct diagnosis and planning optimal management in such cases.     

Antibody reactivities to skeletal muscle proteins in a patient with λ light chain secreting multiple myeloma, generalised amyloidosis and rhabdomyolysis

Rhabdomyolysis is a rare complication in haematological malignancies, and a diverse range of factors has been implicated in the etiology of the syndrome. In the present study we analysed muscle morphology and antibody reactivities to skeletal muscle proteins in a patient diagnosed with lambda (lambda) light chain-secreting multiple myeloma (MM) and amyloidosis, who developed a progressive rhabdomyolysis. The muscle tissue analysis showed focal amyloid depositions and a low degree of atrophy and inflammation. Antibody reactivities against muscle proteins of approximately 42, 51 and 66 kD, respectively, were present in the patient's serum. The antibody specificities were revealed by lambda light chain- or IgM-specific antibodies. The results indicate a possible etiologic link between antibody reactivities towards muscle proteins and muscle tissue disorder in a patient with the unique combination of rhabdomyolysis, amyloidosis and MM of the light chain type.     

The mechanism of cyclosporine toxicity induced by clarithromycin

Aims Recently a number of case reports have described the interaction of clarithromycin with cyclosporine A, resulting in cyclosporine toxicity. This interaction is presumed to take place via the hepatic cytochrome P450 enzyme system.
Methods Following a case of cyclosporine toxicity and acute renal failure in a transplant patient started on clarithromycin, we investigated the effect of oral clarithromycin on the hepatic P450 system in five healthy normal male volunteers, by means of the erythromycin breath test.
Results Cytochrome P4503A (CYP3A) activity was reduced in all subjects by a mean level of 26% following clarithromycin treatment. This would result in a significant reduction in cyclosporine clearance in patients receiving clarithromycin.
Conclusions As clarithromycin was shown to inhibit CYP3A activity in all subjects tested, we recommend that a high degree of caution be exercised when clarithromycin is administered to patients receiving cyclosporine therapy or other drugs known to be eliminated by CYP3A-mediated metabolism.