Proximal myopathy during beta-blockade

Drug-Induced Myopathies: A Comprehensive Review and Update

Drug-induced myopathies are a common cause of muscle pain, and the range of drugs that can cause muscle side effects is constantly expanding. In this article, the authors comprehensively discuss the diagnostic and therapeutic process in patients with myalgia, and present the spectrum of drug-induced myopathies. The review provides a detailed analysis of the literature on the incidence of myopathy during treatment with hypolipemic drugs, beta-blockers, amiodarone, colchicine, glucocorticosteroids, antimalarials, cyclosporine, zidovudine, and checkpoint inhibitors, a group of drugs increasingly used in the treatment of malignancies. The article considers the clinical course of the different types of myopathies, their pathogenesis, histopathological features, and treatment methods of these disorders. The aim of this paper is to gather from the latest available literature up-to-date information on the course, pathophysiology, and therapeutic options of drug-induced myopathies, to systematize the knowledge of drug-induced myopathies and to draw the attention of internists to the fact that these clinical issues are an important therapeutic problem.

Evaluation of antihypertensive drugs in combination with enzyme replacement therapy in mice with Pompe disease

Pompe disease is caused by the deficiency of lysosomal acid α-glucosidase (GAA) leading to progressive myopathy. Enzyme replacement therapy (ERT) with recombinant human (rh) GAA has limitations, including inefficient uptake of rhGAA in skeletal muscle linked to low cation-independent mannose-6-phosphate receptor (CI-MPR) expression.

PURPOSE

To test the hypothesis that antihypertensive agents causing muscle hypertrophy by increasing insulin-like growth factor 1 expression can increase CI-MPR-mediated uptake of recombinant enzyme with therapeutic effects in skeletal muscle.

METHODS

Three such agents were evaluated in mice with Pompe disease (carvedilol, losartan, and propranolol), either with or without concurrent ERT.

RESULTS

Carvedilol, a selective β-blocker, increased muscle strength but reduced biochemical correction from ERT. Administration of drugs alone had minimal effect, with the exception of losartan that increased glycogen storage and mortality either by itself or in combination with ERT.

CONCLUSION

The β-blocker carvedilol had beneficial effects during ERT in mice with Pompe disease, in comparison with propranolol or losartan. Caution is warranted when prescribing antihypertensive drugs in Pompe disease.

Propranolol and the risk of hospitalized myopathy: translating chemical genomics findings into population-level hypotheses

BACKGROUND

A recent large-scale, chemical screening study raised the hypothesis that propranolol may increase the risk of myopathy. We tested this hypothesis in a large population to assess whether (1) propranolol use is associated with an increased risk of myopathy and (2) the concurrent use of propranolol with a statin may further increase risk of myopathy.

METHODS

New users of propranolol and other beta-blockers (BBs) aged >/=65 were identified using data from Medicare and drug benefit programs in 2 states (1994-2005). The primary end point studied was hospitalization for myopathy or rhabdomyolysis. We used stratified Cox proportional hazards regression to estimate the multivariate-adjusted effect of propranolol compared to other BBs and controlled for demographic variables, risk factors for myopathy, other comorbidities, and health service use measures. We also assessed whether co-use of propranolol and statin further increases the risk, by including an interaction term for use of propranolol and statins.

RESULTS

We identified 9,304 initiators of propranolol and 130,070 initiators of other BBs and found 30 cases of hospitalized myopathy in 15,477 person-years (PYs) of propranolol use and 523 in 343,132 PYs of other BB use. Comparing propranolol with other BB users, the adjusted hazard ratio was 1.45 (95% CI 1.00-2.11) for myopathy and 1.48 (95% CI 0.82-2.67) for rhabdomyolysis. We could not detect interaction between propranolol and statins due to limited power. Similar results were observed when propranolol users were compared to other antihypertensive drug users.

CONCLUSIONS

Propranolol may be associated with a 45% increased risk of hospitalized myopathy in the elderly. Our study illustrates how results from in vitro chemical screens can be translated into hypotheses about drug toxicity at the population level.

Mitochondrial Disorder Aggravated by Propranolol

Although there are indications that beta-blockers affect the skeletal muscle in therapeutic dosages, their influence on mitochondrial disorders is unknown. A 52-year-old woman developed double vision, myalgias, muscle cramps, and hip and thigh muscle stiffness. Clinical neurologic examination revealed ptosis, dysarthria, sore neck muscles, weakness and wasting of the thighs, and generally brisk tendon reflexes. Lactate stress testing was significantly abnormal. Needle electromyography was nonspecifically abnormal and myopathic. Muscle biopsy showed mild myopathic changes, target fibers, and a single COX-negative fiber. Probable mitochondrial disorder was diagnosed. The patient had been on 30 mg of propranolol during 7 years for arterial hypertension. Shortly after discontinuation of the drug, her double vision gradually disappeared, myalgias and muscle cramps gradually resolved, and the patient reported an increase in muscle mass on repeated follow-ups. Long-term administration of propranolol may aggravate a mitochondrial disorder. Discontinuation of propranolol may result in a gradual resolution of these adverse reactions.

Iatrogenic and toxic myopathies

There has been increasing awareness of the adverse effects of therapeutic agents and exogenous toxins on the structure and function of muscle. The resulting clinical syndrome varies from one characterized by muscle pain to profound myalgia, paralysis, and myoglobinuria. Because toxic myopathies are potentially reversible, their prompt recognition may reduce their damaging effects or prevent a fatal outcome. Interest in the toxic myopathies, however, derives not only from their clinical importance but also from the fact that they serve as useful experimental models in muscle research. Morphological and biochemical studies have increased our understanding of the basic cellular mechanisms of myotoxicity. Toxins may produce, for instance, necrotizing, lysosomal-related, inflammatory, anti-microtubular, mitochondrial, hypokalemia-related, or protein synthesis-related muscle damage.

Muscle cramps and elevated serum creatine phosphokinase levels induced by beta-adrenoceptor blockers

We have assessed the propensity of beta-adrenoceptor blockers to cause muscle cramps and to raise the serum creatine phosphokinase (CPK) level in 78 patients with essential hypertension. After a control period, a beta-adrenoceptor blocker without intrinsic sympathomimetic activity (ISA; propranolol, metoprolol or arotinolol) was administered for three months. Thereafter, the patients were randomised to receive a beta-adrenoceptor blocker with ISA (pindolol or carteolol) for three months or a beta-adrenoceptor blocker without ISA for a further three months. This pattern was continued until all beta-adrenoceptor blockers had been given. At the end of each period, CPK and CPK-MB levels were measured. Of the 78 subjects, muscle cramps occurred in 27 during treatment with pindolol and 32 during treatment with carteolol. No complaints were made by subjects treated with propranolol and arotinolol, but muscle cramps were reported in 2 treated with metoprolol. While muscle cramps were caused both by pindolol and carteolol in 16 subjects, they were caused by either of these drugs in the remainder of the subjects. Muscle cramp occurred mainly in the calves when the patients were in bed at night. Serum CPK and CPK-MB levels increased significantly during treatment with pindolol (control period vs pindolol, CPK = 96 vs 133 IU.ml-1, CPK-MB = 14 vs 18 IU.ml-1) or carteolol (CPK = 117 IU.ml-1, CPK-MB = 18 IU.ml-1) while the levels during treatment with propranolol, arotinolol and metoprolol did not change from those in the control period.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective beta-adrenoceptor partial agonist effects of pindolol and xamoterol on skeletal muscle assessed by plasma creatine kinase changes in healthy subjects

1. The effects of selective beta-adrenoceptor partial agonist activity on plasma creatine kinase (CK) and skeletal muscle symptoms were studied in normal volunteers. 2. A drug with beta 1-selective partial agonist activity (xamoterol) and one with partial agonist activity acting mainly through beta 2-adrenoceptors (pindolol) were each given for 3 weeks in a randomised double-blind crossover study in 10 subjects. Five additional subjects received only one drug. Plasma CK levels were monitored during a baseline placebo run-in phase, the active treatment period and a placebo washout phase which continued until CK levels returned to baseline. 3. The degree of beta-adrenoceptor antagonism was determined by the inhibition of exercise-induced tachycardia and was similar for the two drug doses used. 4. During pindolol administration plasma CK levels rose compared with pretreatment baseline levels and with levels during xamoterol administration which did not rise. After pindolol was withdrawn CK levels reached higher peaks in some subjects after 1-5 days. 5. Muscle cramps were reported by five subjects during pindolol administration and by one of these subjects but to a lesser extent during xamoterol administration. 6. Pindolol may produce this effect, which was not seen with xamoterol, because of its specific beta 2-adrenoceptor partial agonist activity. Elevations in plasma CK produced by this type of drug or its withdrawal may cause confusion in the diagnosis of muscle disease or myocardial infarction unless the myocardial isoenzyme is measured.

Bucindolol: effects on blood pressure, airways resistance and serum creatine phosphokinase

The effect of bucindolol on pulse, blood pressure and airways resistance was studied in eight patients. One hour after 150 mg bucindolol, a significant decrease in supine, standing and post-exercise blood pressure was observed. No change in blood pressure occurred 10 to 14 h after doses ranging from 50-150 mg indicating that bucindolol has a relatively short duration of action. A dose related inhibition of exercise induced tachycardia was observed consistant with beta-receptor blocking activity. However, there was no change in the resting pulse indicating partial sympathomimetic activity. There was no increase in airways resistance at all doses of bucindolol. Serum creatine phosphokinase increased beyond normal limits in 3 out of 6 patients studied, probably due to a direct effect upon skeletal muscle.

Adverse effects of drugs on muscle

A variety of drugs used in clinical practice may cause myopathy or interfere with neuromuscular transmission. The precise incidence of such disorders is not known, but it is almost certainly higher than is generally suspected. An important aspect of drug-induced muscular disorders is their reversibility if the offending agent is withdrawn, whereas failure to do so may lead to unnecessary morbidity. The study of drug effects on muscle provides a means of investigating the pathological reactions of muscle, and of producing experimental models of naturally occurring myopathies. Drug-induced myopathies may result from a direct toxic effect, which may be local when the drug is injected into a muscle or more diffuse when the drug is taken systemically, or may be secondary to electrolyte disturbances, muscle compression, ischaemia, neural activation or to the development of an immunological reaction directed against muscle. Repeated injections of antibiotics or drugs of addiction may lead to severe muscle fibrosis and contractures. A variety of drugs may cause an acute or subacute painful necrotising myopathy which may be associated with myoglobinuria, at times leading to acute renal failure. Clofibrate and epsilon aminocaproic acid are the drugs most frequently implicated, but a similar syndrome may occur in alcoholics and heroin addicts. Certain hypocholesterolaemic agents may induce myotonia by altering the sterol composition of the muscle cell membrane, while certain drugs including beta-adrenergic blockers and agonists, succinylcholine and diuretics may exacerbate or unmask pre-existing myotonia. In the syndrome of malignant hyperpyrexia, halothane, succinylcholine and various other agents may induce a potentially fatal state of muscular rigidity and hypermetabolism in susceptible individuals as a result of a defect in the calcium transport function of the sarcoplasmic reticulum and possibly of other cellular membranes. In corticosteroid myopathy, which is the most common form of drug-induced myopathy, there is selective atrophy of type 2 muscle fibres and the primary metabolic effect is an inhibition of RNA and protein synthesis, although protein degradation is also increased. Chloroquine and a number of related drugs with amphiphilic cationic properties may induce lysosomal storage myopathy, which may be associated with cardiomyopathy and with a more widespread form of lipidosis.

Adverse effects of antihypertensive drugs

Early essential hypertension is asymptomatic and should remain so throughout treatment. In view of the increasing number of available antihypertensive agents, clinicians need to become familiar with the potential side effects of these drugs. By placing more emphasis on non-pharmacological treatment (sodium restriction, weight loss, exercise) and thoroughly evaluating each case in particular, the pharmacological regimen can be optimally tailored to the patient's needs. Potential side effects should be predicted and can often be avoided; if they become clinically significant they should be rapidly recognised and corrected. These side effects can be easily remembered in most instances, as they fall into 3 broad categories: (a) those caused by an exaggerated therapeutic effect; (b) those due to a non-therapeutic pharmacological effect; and (c) those caused by a non-therapeutic, non-pharmacological effect probably representing idiosyncratic reactions. This review focuses mainly on adverse effects of the second and third kind. Each group of drugs in general shares the common side effects of the first two categories, while each individual drug has its own idiosyncratic side effects.