Ultrastructural pathology in emetine-induced myopathy

Muscle Toxicity of Drugs: When Drugs Turn Physiology into Pathophysiology

Drugs are prescribed to manage or prevent symptoms and diseases, but may sometimes cause unexpected toxicity to muscles. The symptomatology and clinical manifestations of the myotoxic reaction can vary significantly between drugs and between patients on the same drug. This poses a challenge on how to recognize and prevent the occurrence of drug-induced muscle toxicity. The key to appropriate management of myotoxicity is prompt recognition that symptoms of patients may be drug related and to be aware that inter-individual differences in susceptibility to drug-induced toxicity exist. The most prevalent and well-documented drug class with unintended myotoxicity are the statins, but even today new classes of drugs with unintended myotoxicity are being discovered. This review will start off by explaining the principles of drug-induced myotoxicity and the different terminologies used to distinguish between grades of toxicity. The main part of the review will focus on the most important pathogenic mechanisms by which drugs can cause muscle toxicity, which will be exemplified by drugs with high risk of muscle toxicity. This will be done by providing information on key clinical and laboratory aspects, muscle electromyography patterns and biopsy results, and pathological mechanism and management for a specific drug from each pathogenic classification. In addition, rather new classes of drugs with unintended myotoxicity will be highlighted. Furthermore, we will explain why it is so difficult to diagnose drug-induced myotoxicity, and which tests can be used as a diagnostic aid. Lastly, a brief description will be given of how to manage and treat drug-induced myotoxicity.

Pediatric Toxicology

Pediatric patients present unique concerns in the field of medical toxicology. First, there are medicines that are potentially dangerous to small children, even when they are exposed to very small amounts. Clinicians should be wary of these drugs even when young patients present with accidental ingestions of apparently insignificant amounts. Next, over-the-counter laxatives and syrup of ipecac, although not commonly considered abused substances, may be misused in both the setting of Munchausen's syndrome by proxy and in adolescents who have eating disorders. Their use should be considered in any gastrointestinal illness of uncertain origin. Finally, as the use of syrup of ipecac at home now has been discouraged by many, some have explored using activated charcoal at home as a new method of prehospital gastrointestinal decontamination. The literature examining activated charcoal and its use in this capacity is discussed.

Ipecac syrup abuse, morbidity, and mortality: isn't it time to repeal its over-the-counter status?

PURPOSE

To review and address the abuse of ipecac, describing its epidemiology, toxicity, clinical characteristics, and laboratory assessment.

METHODS

A Medline search (1980-2003) for Ipecac abuse and Ipecac toxicity, n = 34.

RESULTS

Ipecac abuse occurs predominantly among adolescent and young adult females who are either experimenting with purging or have an eating disorder. Psychiatric comorbidity is common. Death can occur and is usually of cardiac origin. Morbidity includes myocarditis with arrhythmias, myositis, gastroesophageal pathology, including Mallory Weiss tears, diarrhea, and metabolic abnormalities (alkalosis, hypokalemia, dehydration). The injuries can reverse with cessation of ipecac use. A high index of suspicion is needed for early detection. Classic findings are abnormal EKG and echocardiography and/or elevation of muscle enzymes (CPK, adolase). Emetine, the alkaloid in ipecac, can be confirmed in serum, urine, and tissue by high performance liquid chromatography.

CONCLUSIONS

Ipecac abuse is dangerous, even deadly. However, if abuse is discontinued, cardiac and muscle damage tends to reverse. Were ipecac syrup to remain an over- the-counter medication, or become a prescription medication, more stringent warning labels ought to be included and further education be provided about its toxicity and potential for abuse. Removing ipecac from the over-the-counter category would best eliminate its potential for abuse.

Guideline on the use of ipecac syrup in the out-of-hospital management of ingested poisons

The use of gastric emptying techniques, including ipecac-induced emesis, in the management of poisoned patients has declined significantly in recent years. Historically, poison centers used ipecac syrup in two ways. Ipecac syrup was administered to patients prior to referral to the emergency department in attempts to start the gastric emptying process as early as possible. Additionally, poison centers used ipecac syrup in attempts to keep patients from requiring referral to medical facilities. In these situations, ipecac syrup was administered in the home and poison center staff performed follow-up telephone calls to gauge progress and outcome. Studies to determine the effectiveness of ipecac syrup demonstrate that it induces vomiting in a high percentage of people to whom it is administered and that it decreases the gastrointestinal absorption of ingested substances in a time-dependent fashion. However, the effectiveness of ipecac syrup in affecting patient outcome has not been studied in adequate clinical trials. Its effectiveness in preventing drug absorption has only been documented for a limited number of substances and is substantially reduced if it is given more than 30-90 minutes following ingestion of the toxic material. There are potentially significant contraindications, adverse effects and related problems associated with the use of ipecac syrup. It is the consensus of the panel that the circumstances in which ipecac-induced emesis is the appropriate or desired method of gastric decontamination are rare. The panel concluded that the use of ipecac syrup might have an acceptable benefit-to-risk ratio in rare situations in which: there is no contraindication to the use of ipecac syrup; and there is substantial risk of serious toxicity to the victim; and there is no alternative therapy available or effective to decrease gastrointestinal absorption (e.g., activated charcoal); and there will be a delay of greater than 1 hour before the patient will arrive at an emergency medical facility and ipecac syrup can be administered within 30-90 minutes of the ingestion; and ipecac syrup administration will not adversely affect more definitive treatment that might be provided at a hospital. In such circumstances, the administration of ipecac syrup should occur only in response to a specific recommendation from a poison center, emergency department physician, or other qualified medical personnel. The panel decided not to address the issue of whether ipecac should remain a nonprescription, over-the-counter product. The panel does not support the routine stocking of ipecac in all households with young children but was unable to reach consensus on which households with young children might benefit from stocking ipecac. Instead, the panel concluded that individual practitioners and poison control centers are best able to determine the particular patient population, geographic and other variables that might influence the decision to recommend having ipecac on hand.

Position paper: Ipecac syrup

Syrup of ipecac should not be administered routinely in the management of poisoned patients. In experimental studies the amount of marker removed by ipecac was highly variable and diminished with time. There is no evidence from clinical studies that ipecac improves the outcome of poisoned patients and its routine administration in the emergency department should be abandoned. There are insufficient data to support or exclude ipecac administration soon after poison ingestion. Ipecac may delay the administration or reduce the effectiveness of activated charcoal, oral antidotes, and whole bowel irrigation. Ipecac should not be administered to a patient who has a decreased level or impending loss of consciousness or who has ingested a corrosive substance or hydrocarbon with high aspiration potential. A review of the literature since the preparation of the 1997 Ipecac Syrup Position Statement revealed no new evidence that would require a revision of the conclusions of that Statement.

Congenital myopathies at their molecular dawning

The introduction and application of molecular techniques have commenced to influence and alter the nosology of congenital myopathies. Long-known entities such as nemaline myopathies, core diseases, and desmin-related myopathies have now been found to be caused by unequivocal mutations. Several of these mutations and their genes have been identified by analyzing aggregates of proteins within muscle fibers as a morphological hallmark as in desminopathy and actinopathy, the latter a subtype among the nemaline myopathies. Immunohistochemistry has played a crucial role in recognizing this new group of protein aggregate myopathies within the spectrum of congenital myopathies. It is to be expected that other congenital myopathies marked by inclusion bodies may turn out to be such protein aggregate myopathies, depending on analysis of individual proteins within these protein aggregates and their association with putative gene mutations.

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.

Absorption, distribution and excretion of 3H-labeled cephaeline- and emetine-spiked ipecac syrup in rats

The maximum plasma radioactivity levels of tritium (3H)-labeled cephaeline, (24.3, 28.7 and 40.6 ng eq./mL) were reached at 2.00-3.33 hours following oral dosing of ipecac syrup. The maximum plasma radioactivity levels of 3H-emetine (2.71, 6.47 and 9.62 ng eq./mL) were reached at 1.08-2.33 hours following ipecac syrup administration. The Cmax values of 3H-cephaeline were followed by a biexponential decrease with half-lives t 1/2(lambda z) of 3.45-9.40 hours. On the other hand, the t 1/2 (lambda z)of 3H-emetine were 65.4-163 hours, which revealed a biexponential decrease. The radioactivity of both tritium-labeled compounds was distrbuted maximally in most tissues at 24 hours. For 3H-cephaeline, the maximum radioactivity levels in tissues were approximately 100-150 times greater than in plasma. For 3H-emetine, the radioactivity levels in tissues were approximately 1000-3000 times greater than in plasma. Tissue radioactivity levels decreased at a substantially slower rate than that observed in plasma. Tissue radioactivity of 3H-emetine decreased more slowly than that of 3H-cephaeline. For 3H-cephaeline, the cumulative biliary excretion of radioactivity was 57.5% at 48 hours. The cumulative urinary and fecal excretion of radioactivity in these rats was 16.5% and 29.1%, respectively, of the dose at 48 hours following dosing. For 3H-emetine, the cumulative biliary excretion of radioactivity was 12.5% at 48 hours. The cumulative urinary and fecal excretion of radioactivity was 9.4% and 34.1%, respectively, of the administered dose at 48 hours. The radioactivity level of 3H-emetine remaining in the carcasses at 48 hours was equivalent to approximately 50% of the dose. A portion of each tritium-labeled compound was subjected to entero-hepatic circulation. Thus, the absorption rate of 3H-cephaeline and 3H-emetine was estimated to be approximately 70% on the basis of the data obtained from excretion studies. There was no difference in the absorption process between these two compounds. However, the difference was admitted in the biliary clearance, which is the main excretion route of both compounds. Delayed excretion of 3H-emetine may be primarily due to its resorption as related to entero-hepatic circulation and tissue retention. This study has determined the absorption, distribution and excretion of 3H-cephaeline and 3H-emetine in rats.

Biotransformation of the ipecac alkaloids cephaeline and emetine from ipecac syrup in rats

The metabolism of cephaeline and emetine, which are the primary active components of ipecac syrup, were investigated in rats. Cephaeline-6'-O-glucuronide was found to be a biliary metabolite of cephaeline. Cephaeline (6'-O-demethylemetine) and 9-O-demethylemetine were observed to be enzyme-hydrolyzed biliary metabolites of emetine. Cephaeline was conjugated to glucuronide, while emetine was demethylated to cephaeline and 9-0-demethylemetine, and may be conjugated to glucuronides afterwards. Urine, feces and bile were collected from rats within 48 hours following the administration of ipecac syrup containing tritium (3H)--labeled cephaeline or emetine. Metabolites were separated and quantified by thin layer chromatography (TLC) or high-performance liquid chromatography (HPLC). Biliary and urinary excretion rates of 3H-cephaeline were 57.5% and 16.5% of the dose, respectively. Cephaeline-6'-O-glucuronide was comprised 79.5% of biliary radioactivity and 84.3% of urinary radioactivity. Unchanged cephaeline was detected in 42.4% of the dose in feces. Biliary excretion rate of 3H-emetine was 6.9% of the dose. Emetine, cephaeline and 9-0-demethylemetine comprised 5.8%, 43.2% and 13.6% in hydrolyzed bile, respectively. There were no emetine-derived metabolites in urine or feces. The occurrence of unchanged emetine was 6.8% and 19.7% of the dose in urine and feces, respectively.

Metabolic abnormalities associated with skeletal myopathy in severe anorexia nervosa

The aim of this study was to characterize the metabolic disturbance associated with the skeletal myopathy resulting from extreme weight loss in anorexia nervosa. Muscle function was examined in eight female patients with severe (40%) weight loss due to anorexia nervosa and histologically confirmed myopathy. A wide range of biochemical and hematologic investigations were carried out, including serum enzymes and the response of plasma lactate to ischemic exercise of forearm muscles. All patients showed proximal muscular weakness. A diminished lactate response to ischemic exercise was a consistent finding, and a reduction of serum carnosinase activity was also found. There were no other consistent biochemical or hematologic abnormalities apart from lymphopenia of no clinical consequence. These findings contribute to our understanding of severe protein-energy malnutrition on the musculoskeletal system. The resulting disorder is a metabolic myopathy from which the patients recover rapidly as their nutrition improves. Although the patients admitted to a variety of abnormal eating behaviors, no correlation was found between a specific type of abnormal eating behavior and subsequent biochemical abnormalities. Reinstating appropriate eating behavior will treat the myopathy.

Desmin-related neuromuscular disorders

Desmin, the intermediate filament protein of skeletal muscle fibers, cardiac myocytes, and certain smooth muscle cells, is a member of the cytoskeleton linking Z-bands with the plasmalemma and the nucleus. The pathology of desmin in human neuromuscular disorders is always marked by increased amounts, diffusely or focally. Desmin is highly expressed in immature muscle fibers, both during fetal life and regeneration as well as in certain congenital myopathies, together with vimentin. Desmin is also enriched in neonatal myotonic dystrophy and small fibers in infantile spinal muscular atrophy. Focal accretion of desmin may be twofold, in conjunction with certain inclusion bodies, cytoplasmic and spheroid bodies, and in a more patchy fashion, granulofilamentous material. Both lesions have been found in certain families, affected by a myopathy and/or cardiomyopathy. Other proteins, e.g., dystrophin, vimentin, actin, ubiquitin, and alpha-B crystallin, may also be overexpressed. Desmin pathology may be genetically regulated or may merely reflect profoundly impaired metabolism of several proteins within myofibers.

Emetine myopathy in a patient with an eating disorder

OBJECTIVE

To alert physicians to the dangers of a readily available, non-prescription drug by describing the clinical and pathological features of myopathy due to chronic poisoning with ipecac syrup in a patient with an eating disorder.

CLINICAL FEATURES

A 27-year-old woman presented in 1991 with a right foot drop, followed a few months later by progressive severe neck and limb weakness associated with dysphagia, faecal incontinence and diffuse body ache. It emerged that she had been consuming increasing quantities of ipecac syrup (up to 200 mL per week) for three months to induce vomiting and weight loss. The serum creatine kinase activity was slightly elevated and electromyographic examination results were in keeping with a necrotising proximal myopathic process. Muscle biopsy showed vacuolar degeneration with myofibrilolysis and fine cytoplasmic body formation, consistent with a diagnosis of emetine myopathy.

INTERVENTION AND OUTCOME

The patient was advised to stop taking ipecac and observed for the next few months. The symptoms resolved gradually and strength returned to normal in four months.

CONCLUSION

Chronic emetine toxicity, with its potentially catastrophic consequences, should be remembered in the evaluation of neuromuscular symptoms in young women, in whom eating disorders are common and often unrecognised.

Ipecac myopathy and cardiomyopathy

Two cases of ipecac myopathy, one with associated cardiomyopathy are reported. Both patients were young women with eating disorders who came to medical attention because of diffuse muscle weakness. Clinical and electromyographic data suggested ipecac myopathy and muscle biopsies confirmed this diagnosis. One patient had associated clinical and echocardiographic evidence of significant cardiomyopathy. The myopathy resolved and the echocardiogram returned to normal after discontinuing the use of ipecac.

Experimental emetine myopathy: enzyme histochemical, electron microscopic, and immunomorphological studies

Ipecac, containing emetine hydrochloride, is used by patients with anorexia nervosa to induce vomiting. Its chronic usage may result in a myopathy and a cardiomyopathy, the former marked by cytoplasmic bodies. We studied myopathological changes after daily injections of female Wistar rats with emetine hydrochloride intraperitoneally for periods of 4, 5, 9, and 10 weeks. The extensor digitorum longus muscle and the soleus muscle showed core-like lesions, streaming of the z-discs, nemaline bodies, cytoplasmic bodies, and spheroid cytoplasmic bodies. Immunomorphological studies revealed increased amounts of desmin. During a period of repair, i.e., 2, 4, and 6 weeks after termination of emetine application, these myopathological alterations faded while proliferation of the T-tubular system, i.e., honeycomb structures, was more often prevalent. Pathological features completely disappeared between 6 and 12 weeks of recovery.

Congenital myopathies

About forty different congenital myopathies (CM) are defined by clinical and morphological criteria. Classical types like central core disease, centronuclear myopathy, and nemaline/rod myopathy are now well established and recognized as neuromuscular conditions. Clinical subtypes as infantile, juvenile, and adult forms have been recognized in several CM. Not infrequently, different disease-specific morphological features may occur in muscle tissue of the same patient combined. Other CM are marked by aggregates of desmin filaments indicating the importance of recent immunohistochemical techniques. Modern myopathological techniques enabled nosological separation of CM, immunohistochemistry, actually, may usher in a new period of research in and understanding of CM. However, application of molecular genetic and molecular biological methods to CM may clarify still unsolved aspects of gene localisation for which the hereditary nature of many CM is particularly conducive, aspects of heterogeneity versus homogeneity of certain CM or clinical variants, of prenatal diagnosis of CM, of pathogenetic and nosological significance of muscle fiber proteins in CM, and of a new nosological classification of CM.

Desmin and actin associated with cytoplasmic bodies in skeletal muscle fibers: immunocytochemical and fine structural studies, with a note on unusual 18- to 20-nm filaments

In a fine structural and immunocytochemical study, the latter performed on semithin sections of epoxy resin embedded skeletal muscle fibers, three types of cytoplasmic bodies were identified in a case of cytoplasmic body myopathy: (1) The first type, the classical type, showed a central core and a light halo with radiating actin filaments at the periphery. (2) The second type, the spheroid body was characterized by irregularly arranged granular masses associated with intermediate filaments. Desmin immunoreactivity occurred in the central and peripheral parts, where filaments of intermediate size were visualized by electron microscopy. Desmin immunoreactivity was noted also at the Z-bands of striated annulets, within areas of disordered myofibrils, such as sarcoplasmic masses, and in atrophic muscle fibers. (3) The third type of the cytoplasmic body was composed mainly of large masses of uneven granularity and electron density. The center of this type reacted to anti-actin antibody suggesting that the 5- to 6-nm filaments, which ultrastructurally proved to be a major component, were of the actin type. By contrast, neither intermediate filaments nor actin microfilaments were found by electron microscopy in cytoplasmic bodies in a second case where no immunoreaction to desmin or actin occurred. Anti-vimentin antibody stained only the cytoplasm of endomysial cells, but not the inclusion bodies. Some other, unusual inclusions with 18- to 20-nm tubulo-filamentous structures have to be distinguished from the various types of filaments in cytoplasmic bodies. It is concluded, that pleomorphism and heterogeneity of "cytoplasmic bodies" have to be taken into consideration when classifying cytoplasmic body myopathies.

Transient cytoplasmic bodies in muscle of three infants with Werdnig-Hoffmann disease

We present three instances in which cytoplasmic bodies in muscle fibers were associated with Werdnig-Hoffmann disease. The children presented within the first 6 weeks of life with clinical symptoms and laboratory studies indicative of infantile spinomuscular atrophy (ISMA). Initial muscle biopsies in each case revealed signs of muscle immaturity and cytoplasmic bodies but lacked features of denervation. Follow-up biopsies in 2 cases revealed changes typical of ISMA, but cytoplasmic bodies were no longer present. A follow-up biopsy was not available in the third child who also had a clinical course consistent with ISMA. We discuss the pathogenesis of cytoplasmic bodies and their significance in association with Werdnig-Hoffmann disease.

Reversible emetine-induced myopathy with ECG abnormalities: a toxic myopathy

A young anorexic woman is described with a history of progressive muscle weakness following chronic ingestion of syrup of ipecac that was used in an attempt at weight control. Electrocardiogram (ECG) showed T-wave inversion in all leads and prolongation of the Q-T interval. Electromyography was abnormal. Muscle biopsy revealed a randomized, generalized, predominantly type-2 fibre atrophy and structural alterations in oxidative enzyme stains, such as targetoid and moth-eaten fibres. A few necrotic cells were actively phagocytosed. Electron microscopy revealed severe sarcomeric abnormalities with Z-line streaming, myofibrillar disorganization and increased lysosomal activity. After discontinuation of ipecac syrup, the patient noted a gradual improvement in her condition. The ECG became normal. Emetine and related drug-induced myopathies are uncommon but are of experimental interest because of their effects on mitochondria and the light they shed on autophagic mechanisms in muscle.