Interaction between orlistat and antihypertensive drugs

The safety profiles of orlistat and sibutramine: results of prescription-event monitoring studies in England

INTRODUCTION

Observational cohort studies were conducted using prescription-event monitoring (PEM) to examine the safety profiles of the anti-obesity agents orlistat and sibutramine. Adverse events reported as case reports were also evaluated to determine whether these events were also identified by PEM.

RESEARCH METHODS AND PROCEDURES

Patients were identified from dispensed prescriptions written by general practitioners (GPs) in England for orlistat or sibutramine. Patient demographic and clinical event information, including reasons for stopping and adverse drug reactions, were requested on questionnaires posted to GPs at least 6 months after the first prescription for individual patients. Event incidence densities (IDs) (number of first reports of event/1000 patient-months treatment) were calculated for month 1 (ID(1)) and months 2-3 (ID(2-3)). Published case reports were identified by searching Medline and Embase.

RESULTS

The cohorts comprised 16,021 and 12,336 patients prescribed orlistat and sibutramine, respectively. Both cohorts had a median age of 45 years, and approximately 80% were female. The most common reason for stopping orlistat within 3 months was diarrhea (332 patients; 2.1% cohort), and for stopping sibutramine it was hypertension (203 patients; 1.6%). Clinical events significantly associated with taking orlistat were mainly gastrointestinal and those for sibutramine included central nervous system effects, nausea/vomiting, palpitation, and sweating. We identified 8 published case reports for orlistat and 10 for sibutramine that had equivalent or similar events assessed as causally related in the PEM studies.

CONCLUSIONS

The PEM studies highlighted different adverse event profiles for orlistat and sibutramine that were consistent with their distinct pharmacological mechanisms and other published information.

Safety of drug therapies used for weight loss and treatment of obesity

Some of the medications used for weight loss in the management of obesity have been associated with unacceptable morbidity and mortality. Safety concerns have led to the withdrawal of aminorex, followed by the fenfluramines in 1997, and phenylpropanolamine (norephedrine) in 2000. Aminorex was associated with an increased prevalence of primary pulmonary hypertension (PPH), fenfluramines with an increased prevalence of PPH and valvulopathy, and phenylpropanolamine with an increased risk of haemorrhagic stroke. Several studies have investigated the safety of the fenfluramines, yet the benefit-risk profile has not been conclusively quantified. This is due to several deficiencies in the published studies, including a lack of data on the baseline prevalences of comorbid conditions in obese subjects, and potential confounders and biases in the study designs. Although several studies and systematic reviews support an increased risk of PPH and valvulopathy in patients who have taken fenfluramines, without knowledge of the background prevalence it is not possible to determine if the exposure preceded the outcome. The population at higher risk of these adverse effects includes those taking higher doses or with a longer duration of exposure to fenfluramines and those with pre-existing cardiac disease or a genetic predisposition. Patients exposed to fenfluramines continue to be monitored, with some follow-up studies indicating no overall worsening in valvulopathy over time. There are limited efficacy and safety data for amfepramone (diethylpropion) and phentermine and their approval for the management of obesity is limited to short-term use. Orlistat and sibutramine are the only currently approved medications for long-term management of obesity. Although the benefit-risk profiles of sibutramine and orlistat appear positive, sibutramine continues to be monitored because of long-term safety concerns. The safety and efficacy of currently approved drug therapies have not been evaluated in children and elderly patient populations and there is limited information in adolescents, whilst the long-term safety of current and potential new drug therapies in adults will require several years of postmarketing surveillance to fully elucidate their adverse effect profiles.

Orlistat use in type 2 diabetes

OBJECTIVE

To review the use of orlistat in type 2 diabetes.

DATA SOURCES

A MEDLINE search of the English-language literature (1990-August 2001) was performed using the key terms orlistat, obesity, glucose, and diabetes.

DATA EXTRACTION

All articles pertaining to orlistat were considered for inclusion, with emphasis placed on randomized, placebo-controlled, double-blind clinical trials.

DATA SYNTHESIS

In April 1999, orlistat was approved by the Food and Drug Administration for the treatment of obesity. Of 13 randomized, placebo-controlled studies, only 2 reported specific data in individuals with type 2 diabetes. Both reported significant weight reduction and improved glycemic control over placebo.

CONCLUSIONS

Since weight loss is a difficult goal to achieve in patients with type 2 diabetes, orlistat can be a safe, effective addition to a multidisciplinary approach.