A retrospective review of California poison control system data of sibutramine exposures

Sibutramine Associated Cardiac Arrest in a Chinese Healthy Young Lady

Sibutramine is a slimming agent and acts on reducing appetite and increasing satiety. It was withdrawn from the market world-wide, including Hong Kong, since November 2010 due to its side effects on the cardiovascular system. However, sibutramine is still commonly found as adulterant in the slimming medications which could be bought from internet or over-the-counter. A Chinese healthy young lady developing sudden cardiac arrest after taking sibutramine for weight reduction is described.

Transient thyrotoxicosis from thyroiditis induced by sibutramine overdose

Sibutramine is an antiobesity drug that inhibits the reuptake of serotonin and noradrenalin in the hypothalamus. A 37-year-old Korean man presented to the emergency room for the oral intake of 280 mg of sibutramine. The patient was in thyrotoxic state. The 99mTechnetium-pertechnetate thyroid scan showed irregular uptake of radioisotope and thyroid-stimulating hormone receptor antibody and thyroperoxidase antibody were negative. Thyroid function normalized after that. The patient had transient thyrotoxicosis with thyroiditis. We report a case of thyrotoxicosis accompanied by thyroiditis resulting from the intentional overdose of sibutramine.

Serotonin syndrome following overdose of a non-prescription slimming product containing sibutramine: a case report

INTRODUCTION

Non-prescription slimming products are popular and can be easily purchased from the Internet. However, adulteration of these products with undeclared substances including prescription drugs is not uncommon. We report a case of serotonin syndrome after an overdose of a non-prescription product containing sibutramine.

CASE REPORT

A 21-year-old woman presented with somnolence, sinus tachycardia, generalised increase in tone, hyper-reflexia and clonus more prominent in the lower limbs after an intentional overdose of a non-prescription slimming product obtained from the Internet. The product was later found to contain sibutramine and other substances such as animal thyroid tissues, caffeine and phenolphthalein. Quantitative analysis of patient's serum on presentation revealed a sibutramine concentration of 112 ng/mL, which far exceeded the reported peak serum concentration after a single oral dose of 15 mg (the maximum daily recommended dose). No other culpable agent was identified. The overall clinical presentation was compatible with serotonin syndrome associated with sibutramine overdose. The patient made a full recovery after supportive management.

DISCUSSION AND CONCLUSION

This case highlighted the health threat posed by non-prescription slimming products sold over the Internet. Sibutramine overdose can result in serotonin syndrome, as in overdose of other serotonergic agents. Early recognition and timely supportive treatment are essential to ensure a good clinical outcome.

Cardiovascular risk-benefit profile of sibutramine

Sibutramine is a combined norepinephrine and serotonin reuptake inhibitor used as an antiobesity agent to reduce appetite and promote weight loss in combination with diet and exercise. At a daily dose of 10-20 mg, it was initially considered to have a good safety profile, as it does not induce primary pulmonary hypertension or adverse effects on cardiac valves, in contrast to previous reports relating to some other antiobesity agents. However, it exerts disparate effects on cardiovascular risk factors. On the one hand, sibutramine may have antiatherogenic activities, as it improves insulin resistance, glucose metabolism, dyslipidemia, and inflammatory markers, with most of these effects resulting from weight loss rather than from an intrinsic effect of the drug. On the other hand, because of its specific mode of action, sibutramine exerts a peripheral sympathomimetic effect, which induces a moderate increase in heart rate and attenuates the reduction in BP attributable to weight loss or even slightly increases BP. It may also prolong the QT interval, an effect that could induce arrhythmias. Because of these complex effects, it is difficult to conclude what the final impact of sibutramine on cardiovascular outcomes might be. Sibutramine has been shown to exert favorable effects on some surrogate cardiovascular endpoints such as reduction of left ventricular hypertrophy and improvement of endothelial dysfunction. A good cardiovascular safety profile was demonstrated in numerous 1- to 2-year controlled trials, in both diabetic and nondiabetic well selected patients, as well as in several observational studies. However, since 2002, several cardiovascular adverse events (hypertension, tachycardia, arrhythmias, and myocardial infarction) have been reported in sibutramine-treated patients. This led to a contraindication of the use of this antiobesity agent in patients with established coronary heart disease, previous stroke, heart failure, or cardiac arrhythmias. SCOUT (Sibutramine Cardiovascular and Diabetes Outcome Study) was designed to prospectively evaluate the efficacy/safety ratio of sibutramine in a high-risk population. The efficacy/safety results of the first 6-week lead-in open period of treatment with sibutramine 10 mg/day were reassuring in 10 742 overweight/obese high-risk subjects (97% had cardiovascular disease, 88% had hypertension, and 84% had type 2 diabetes mellitus). However, the final results of SCOUT showed that long-term (5 years') treatment with sibutramine (10-15 mg/day) exposed subjects with pre-existing cardiovascular disease to a significantly increased risk for nonfatal myocardial infarction and nonfatal stroke, but not cardiovascular death or all-cause mortality. Because the benefit of sibutramine as a weight-loss aid seems not to outweigh the cardiovascular risks, the European Medicines Agency recommended the suspension of marketing authorizations for sibutramine across the EU. The US FDA stated that the drug should carry a 'black box' warning due to an increased risk of stroke and heart attack in patients with a history of cardiovascular disease. In conclusion, concern still persists about the safety profile of sibutramine regarding cardiovascular outcomes, and the drug should not be prescribed for overweight/obese patients with a high cardiovascular risk profile.