Retrospective population-based analysis of the dose-response (fecal fat excretion) relationship of orlistat in normal and obese volunteers

[Current status of the treatment of type 2 diabetes mellitus. The revival of insulin-resistance drugs]

The relief of insulin resistance is one of the two therapeutic targets of the treatment of type 2 diabetes. Insulin-sensitizers are therefore complemental with other oral diabetic drugs. The treatment of insulin resistance was for a long time limited to dietary and exercise programmes, a biguanide, metformine, and benfluorex, a phenylethylamine derivative; the mechanisms of action of both drugs are now better understood and their indications more precisely targeted. A new therapeutic class, the thiazolidinediones (troglitazone, rosiglitazone, pioglitazone) has recently completed the family of insulin-sensitizing agents. These drugs, which should be soon available in France, act by a different way than metformin, which has been recently identified as the peroxisomes proliferator-activated receptor. The role of antilipolytic agents, which might increase glucose uptake by reducing free fatty acid production and oxidation is under evaluation, as well as the potential benefit of orlistat, an inhibitor of lipid digestion which has been proved effective, in addition to hypocaloric diet, in the management of obese patients.

Current concepts in the pharmacological management of obesity

The pharmacological management of obesity has gained increasing attention as new weight loss treatments are approved and a significant proportion of the public strives to lose weight. Obesity is associated with a high mortality rate, multiple chronic medical conditions, and carries an enormous financial burden. Obesity is a multifactorial condition, most often due to an imbalance in energy intake and expenditure. Despite the greater focus on management of obesity, weight loss remains a difficult goal to achieve. Obesity is a chronic medical condition that may require long term treatment, therefore the risks and benefits of all pharmacological agents must be carefully considered. Noradrenergic appetite suppressants (ie. phenyl-propanolamine, phentermine) result in weight loss but stimulatory effects limit their use. The serotonergic agents (fenfluramine, dexfenfluramine) were effective weight loss drugs, but were voluntarily withdrawn from the US market last year because of cardiovascular and pulmonary complications. The combination noradrenergic/serotonergic agent sibutramine is indicated for the management of obesity, particularly in the presence of other cardiovascular risk factors. Modest weight loss is achieved with sibutramine, although weight gain is significant after discontinuation. In addition, long term safety data are not yet available. The thermogenic combination of ephedrine plus caffeine is minimally effective, and adverse effects are usually transient. Other thermogenic agents, such as beta3-agonists, are still under investigation. Agents may alter digestion through lipase inhibition (orlistat) or fat substitution (olestra). Orlistat decreases systemic absorption of dietary fat, decreasing body weight and cholesterol. Olestra is a fat substitute that has been incorporated into snack foods. Olestra substitution for dietary fat has not been studied as a weight loss strategy, although olestra has no caloric value and may be beneficial. The use of orlistat and olestra may be limited by gastrointestinal adverse effects. Finally, the manipulation of leptin and neuropeptide Y are under investigation for the treatment of obesity. Pharmacological agents should be used as an aid to a structured diet and exercise regimen in the treatment of obesity. Weight loss agents may result in initial weight loss, but sustained weight loss is not always achieved even with continuation of treatment. The effect of weight loss obtained while using pharmacotherapeutic agents on morbidity and mortality has not been established. Therefore, diet and exercise should be the focus of any weight loss programme. There is a continued need for safe and effective pharmacotherapeutic agents for the treatment of obesity.

Orlistat, a lipase inhibitor, for weight maintenance after conventional dieting: a 1-y study

BACKGROUND

Long-term maintenance of weight loss remains a therapeutic challenge in obesity treatment.

OBJECTIVE

This multicenter, double-blind, placebo-controlled study was designed to test the hypothesis that orlistat, a gastrointestinal lipase inhibitor, is significantly more effective than a placebo in preventing weight regain.

DESIGN

Obese subjects who lost > or = 8% of their initial body weight during a 6-mo lead-in of a prescribed hypoenergetic diet (4180-kJ/d deficit) with no adjunctive pharmacotherapy were randomly assigned to receive placebo, 30 mg orlistat, 60 mg orlistat, or 120 mg orlistat 3 times daily for 1 y in combination with a maintenance diet to help prevent weight regain. Of 1313 recruited subjects [body mass index (in kg/m2): 28-43], 729 subjects lost > or =8% of their initial body weight during the 6-mo weight-loss lead-in period and were enrolled in the double-blind phase.

RESULTS

After 1 y, subjects treated with 120 mg orlistat 3 times daily regained less weight than did placebo-treated subjects (32.8 +/- 4.5% compared with 58.7 +/- 5.8% regain of lost weight; P < 0.001). Moreover, more subjects in the 120-mg orlistat group than in the placebo group regained < or = 25% of lost weight (47.5% of subjects compared with 29.9%). In addition, orlistat treatment (120 mg 3 times daily) was associated with significantly greater reductions in total and LDL-cholesterol concentrations than was placebo (P < 0.001).

CONCLUSION

The use of orlistat during periods of attempted weight maintenance minimizes weight readjustment and facilitates long-term improvement in obesity-related disease risk factors.

Insulin resistance, impaired glucose tolerance and non-insulin-dependent diabetes, pathologic mechanisms and treatment: current status and therapeutic possibilities

Impaired glucose tolerance and non-insulin-dependent diabetes (NIDDM) are the pathologic consequence of two co-incident and interacting conditions, namely insulin resistance and relative insulin deficiency. Recognised by the World Health Authority as a global health problem there are at 1995 estimates at least 110 million diagnosed diabetics world wide with at least the same number undiagnosed. Diabetes is the 4th leading cause of death in developed countries and its management exerts a vast economic and social burden. Insulin resistance is established as the characteristic pathologic feature of patients with glucose intolerance and NIDDM describing a state in which insulin stimulated glucose uptake and utilisation in liver, skeletal muscle and adipose tissue is impaired and coupled to impaired suppression of hepatic glucose output. Although the biochemical mechanisms underpinning both defects are becoming better understood, the genetic and molecular causes remain elusive; and whether insulin resistance or relative insulin deficiency represents the primary defect in patients with NIDDM is the matter of some debate. In this article we review the biochemical and molecular nature of the defects in insulin sensitivity and glucose uptake, and discuss some of the potential causative mechanisms. The genetic and environmental basis of insulin resistance is reviewed and presented, and potential therapeutic targets including thiazolidinediones are discussed.

Long-term systemic exposure of orlistat, a lipase inhibitor, and its metabolites in obese patients

Orlistat, a lipase inhibitor, acts locally in the gastrointestinal tract; its systemic exposure is not required for its efficacy. However, knowledge of the extent of its systemic exposure is important for its safe use in obese patients, the intended target population. Pharmacokinetic screening in obese patients was carried out by monitoring plasma concentrations of unchanged orlistat and its metabolites in five key double-blind, placebo-controlled phase II/III studies. Results of these studies involving the monitoring of plasma samples indicate that detection of intact orlistat in plasma was sporadic, and measurable concentrations were low (< 10 ng/mL or 0.02 microM) without evidence of accumulation, which is consistent with minimal absorption. It is concluded that systemic exposure of orlistat is negligible; at a clinically efficacious dose level, orlistat is unlikely to produce systemic lipase inhibition.

Obesity medications and the treatment of type 2 diabetes

Obesity is a chronic disease and requires ongoing treatment. Type 2 diabetes is associated with obesity and improves with weight loss. Diets of 800 kcal/d induce twice the weight loss induced by weight loss medications. The strength of weight loss medication, which should be used with diet and a lifestyle change program, is the maintenance of weight loss. Sibutramine and orlistat are the only two medications approved for the long-term treatment of obesity. Orlistat gives a reduction of low-density lipoprotein (LDL) cholesterol in excess of that expected with weight loss, and the drop in blood pressure expected with weight loss is not seen with sibutramine. Except in newly diagnosed patients with diabetes subjects, patients with diabetes lose half the weight of subjects who do not have diabetes when treated with weight loss medications. Metformin and, to a lesser extent, acarbose cause weight loss, making them attractive choices for the treatment of obese type 2 diabetic subjects. Repaglinide appears to be weight-neutral, but other medications for patients with diabetes can be associated with weight gain. Many new medications are in development for the treatment of obesity. These new medications act through a variety of mechanisms and will surely play an increasingly important role in the treatment of obese patients with type 2 diabetes.

Treatment with orlistat reduces cardiovascular risk in obese patients

OBJECTIVE

To study the efficacy of orlistat, as an adjunct to dietary modification, in weight reduction and modification of cardiovascular risk factors in obese patients after 1 year of treatment

DESIGN

A total of 3132 obese patients (body mass index 28-43 kg/m2) were evaluated in an analysis of pooled data from five randomized, double-blind, placebo-controlled trials of orlistat in conjunction with a hypocaloric diet. All studies included a 4-week, single-blind, placebo lead-in period during which patients followed a mildly hypocaloric diet, after which they were randomized to double-blind treatment with orlistat 120 mg three times a day (tid) or placebo for 1 year.

RESULTS

After 1 year, orlistat 120 mg tid produced significantly more weight loss than placebo (9.2% vs 5.8%; P< 0.001). Furthermore, a greater proportion of orlistat-treated patients lost >5% or >10% of their initial body weight compared to placebo (69.6% vs 51.9%; P< 0.001 and 42.1% vs 22.7%; P< 0.001, respectively). Improvements in cardiovascular risk factors were observed during a 4-week placebo lead-in period. However, following randomization, orlistat-treated patients had significantly greater improvements than placebo-treated patients in several lipid parameters including total cholesterol, low-density lipoprotein-cholesterol, triglycerides, and apolipoprotein B. In addition, orlistat had a beneficial effect on oral glucose tolerance tests status, waist circumference and systolic and diastolic blood pressure. Orlistat was well tolerated and had a similar safety profile to placebo.

Randomised placebo-controlled trial of orlistat for weight loss and prevention of weight regain in obese patients. European Multicentre Orlistat Study Group

BACKGROUND

We undertook a randomised controlled trial to assess the efficacy and tolerability of orlistat, a gastrointestinal lipase inhibitor, in promoting weight loss and preventing weight regain in obese patients over a 2-year period.

METHODS

743 patients (body-mass index 28-47 kg/m2), recruited at 15 European centres, entered a 4-week, single-blind, placebo lead-in period on a slightly hypocaloric diet (600 kcal/day deficit). 688 patients who completed the lead-in were assigned double-blind treatment with orlistat 120 mg (three times a day) or placebo for 1 year in conjunction with the hypocaloric diet. In a second 52-week double-blind period patients were reassigned orlistat or placebo with a weight maintenance (eucaloric) diet.

FINDINGS

From the start of lead-in to the end of year 1, the orlistat group lost, on average, more bodyweight than the placebo group (10.2% [10.3 kg] vs 6.1% [6.1 kg]; LSM difference 3.9 kg [p<0.001] from randomisation to the end of year 1). During year 2, patients who continued with orlistat regained, on average, half as much weight as those patients switched to placebo (p<0.001). Patients switched from placebo to orlistat lost an additional 0.9 kg during year 2, compared with a mean regain of 2.5 kg in patients who continued on placebo (p<0.001). Total cholesterol, low-density lipoprotein (LDL) cholesterol, LDL/high-density lipoprotein ratio, and concentrations of glucose and insulin decreased more in the orlistat group than in the placebo group. Gastrointestinal adverse events were more common in the orlistat group. Other adverse symptoms occurred at a similar frequency during both treatments.

INTERPRETATION

Orlistat taken with an appropriate diet promotes clinically significant weight loss and reduces weight regain in obese patients over a 2-year period. The use of orlistat beyond 2 years needs careful monitoring with respect to efficacy and adverse events.

Update on the pharmacotherapy of obesity

OBJECTIVE

To review recent developments in the pharmacotherapy of obesity, including the agents currently approved for use in the management of obesity and those under development.

DATA SOURCES

A MEDLINE search from January 1990 to July 1997 was conducted to identify English literature available on the pharmacotherapy of obesity. The search was supplemented by a review of the bibliographies of identified literature.

STUDY SELECTION

All controlled and uncontrolled trials were reviewed. When available, double-blind, placebo-controlled trials were used preferentially.

DATA EXTRACTION

Agents were reviewed with regard to mechanism of action, clinical trial data regarding efficacy, adverse effects, pharmacokinetics, drug interactions, and contraindications where information was available. Study design, selected population, results, and adverse effect information were included.

DATA SYNTHESIS

The anorexiants currently available or under development for the management of obesity regulate food intake and satiety via the adrenergic and/or serotonergic pathways. Clinical trials have shown a 10-15% weight loss can typically be anticipated; however, little long-term safety and efficacy data are available. Adverse events tend to be mild and self-limiting, but serious adverse events can occur. Treatment options under development include thermogenic agents, digestive inhibitors, and analogs and antagonists of hormones that regulate food intake and satiety.

CONCLUSIONS

Several mechanisms to control weight are currently under investigation for the management of obesity. Since obesity is a chronic condition, further studies should be conducted to evaluate the long-term safety and efficacy of these agents and the role of combination therapy using different modalities.

Metabolic profiles of minimally absorbed orlistat in obese/overweight volunteers

To determine the metabolic profile of minimally absorbed orlistat in obese/overweight patients, an open-label, single-dose study was performed in eight obese/overweight volunteers between 23 and 68 years of age. Each subject received a single oral dose of 360 mg orlistat containing approximately 400 muCi of 14C-labeled orlistat. Serial blood samples were collected at specified times over 10 hours after administration of orlistat for determination of total radioactivity, unchanged orlistat, and major metabolites in the plasma. Urine samples were collected over 24 hours and analyzed to evaluate the urinary recovery of total radioactivity and the profile of orlistat metabolites in the urine. In addition, all fecal samples were collected and analyzed for total radioactivity. Urinary and fecal recovery of the administered dose of total radioactivity were 1.13 +/- 0.50% (24-hour data only) and 96.4 +/- 18.1% (n = 7), respectively. Maximum observed concentration (Cmax) and time to Cmax (tmax) values of plasma total radioactivity were 150 +/- 51 ng.eq/mL and 6.8 +/- 1.5 hrs, respectively. All these parameters obtained in obese/ overweight subjects were similar to those reported previously in healthy subjects. On the basis of the area under the concentration-time curve from 0 to 10 hours (AUC0-10), two major metabolites comprise a total of approximately 42% of the total radioactivity in plasma. The primary metabolite (M1) has a short half-life (approximately 2 hours), whereas the secondary metabolite (M3) disappeared at a slower rate. No strikingly apparent difference in the urinary metabolic profile was observed between two gender groups. It is concluded that the disposition of orlistat appears to be similar between normal and obese/overweight subjects. Of the minimal fraction of the dose that was absorbed systemically, the presence of two major metabolites accounts for approximately 42%.

The effect of orlistat on the pharmacokinetics of phenytoin in healthy volunteers

To assess the effect of an orlistat-induced reduction in dietary fat absorption on the pharmacokinetics of phenytoin, a third-party blind, placebo-controlled, randomized, two-way crossover study was performed in 12 healthy volunteers. Each participant received single 300-mg oral doses of phenytoin administered on the fourth day of treatment with 120 mg orlistat (treatment A) or placebo (treatment B) three times a day for 7 days. The two treatments were separated by a 2-week washout period. Serial blood samples were collected before and up to 96 hours after each dose of phenytoin to determine serum concentrations of phenytoin. The 90% confidence intervals (CI) for the ratio of geometric least-squares means for maximum concentration (Cmax) and area under the concentration-time curve (AUC) and for the difference of arithmetic least-squares means for time of maximum concentration (tmax) and elimination rate constant (lambda z) showed the two treatments of phenytoin to be equal by analysis of variance. An approximately 30% reduction in dietary fat absorption induced by orlistat administered at doses of 120 mg three times daily did not significantly alter the pharmacokinetics of a single 300-mg oral dose of phenytoin in healthy volunteers.

The effect of orlistat on the pharmacokinetics and pharmacodynamics of warfarin in healthy volunteers

To assess the effect of orlistat on the pharmacokinetics and pharmacodynamics of warfarin, a third-party blind, placebo-controlled, randomized, two-way crossover study was performed in 12 healthy volunteers. Each participant received single 30-mg oral doses of racemic warfarin sodium (Coumadin; DuPont Pharma, Wilmington, DE) administered on the eleventh day of treatment with 120 mg orlistat (treatment A) and placebo (treatment B) three times a day for 16 days; the two treatments were separated by a 3-week washout period. Serial blood samples were collected before and at appropriate intervals after each dose of warfarin to determine plasma concentrations of R-warfarin and S-warfarin and blood prothrombin time (PT) and plasma Factor VII concentration. In addition, serum concentrations of vitamin K1 and its epoxide and of osteocalcin and its undercarboxylated form were measured before breakfast on days -7, 1, 4, 6, and 10. Equivalent results between treatments with orlistat and placebo were found with regard to all pharmacokinetic parameters of R- and S-warfarin (except for time to maximum concentration of R-warfarin). Pharmacodynamic parameters of warfarin (PT and Factor VII) and vitamin K nutritional status parameters (ratios of vitamin K1 to vitamin K1 epoxide and undercarboxylated osteocalcin to osteocalcin) also were unaltered by orlistat. Orlistat administered at doses of 120 mg three times daily did not significantly alter the pharmacokinetics and pharmacodynamics of a single 30-mg oral dose of warfarin in healthy volunteers.

The effect of orlistat, an inhibitor of dietary fat absorption, on the absorption of vitamins A and E in healthy volunteers

An open-label, placebo-controlled, randomized, two-way crossover study was performed in 12 healthy volunteers (between 20 and 44 years of age) to assess the effect of orlistat, a gastrointestinal lipase inhibitor that reduces dietary fat absorption and is being developed for weight control in obesity, on the absorption of vitamins A and E. Each participant received a single oral dose of 25,000 IU vitamin A followed 24 hours later by a single oral dose of 400 IU vitamin E on two separate occasions: during oral administration of 120 mg orlistat or placebo three times daily for 9 days. The two treatments were separated by a washout period of at least 2 weeks. Serial blood samples for pharmacokinetic analysis were collected at specified times over 24 hours after each dose of vitamin A for determination of serum concentrations of retinol, and over a period of 5 days after each dose of vitamin E for determination of serum concentrations of alpha-tocopherol, total cholesterol, and triglycerides. Orlistat significantly reduced the absorption of vitamin E (approximately 43% according to maximum concentration and approximately 60% according to area under the concentration-time curve), but not that of vitamin A, at the dose levels studied. The results of this study will aid in the implementation of a vitamin supplementation strategy, should vitamin deficiency occur in patients undergoing orlistat therapy.

Lack of effect of orlistat on the bioavailability of a single dose of nifedipine extended-release tablets (Procardia XL) in healthy volunteers

Orlistat, a lipase inhibitor, reduces dietary fat absorption, and thus could potentially alter the absorption of some concomitantly administered drugs, such as the nifedipine gastrointestinal therapeutic system (GITS). To assess the effect of orlistat on the bioavailability of nifedipine GITS, a third party-blind, placebo-controlled, randomized, two-way crossover study was performed in 18 healthy volunteers. Each participant received single 60-mg oral doses of nifedipine GITS (Procardia XL; Pfizer Labs, New York, NY) on the fourth day of treatment with 120 mg of orlistat or placebo three times a day for 6 days. The two treatments were separated by a washout period of at least 1 week. Serial blood samples were collected before and at appropriate intervals after each nifedipine dose to determine plasma concentrations of nifedipine. The 90% confidence intervals for the ratio of geometric least-square means for maximum concentration (C(max)) and area under the concentration-time curve (AUCo-t) and for the difference of arithmetic least-square means for time to maximum concentration (t(max)) indicate that the bioavailability of nifedipine was not altered by treatment with orlistat. Therapeutic doses of 120 mg of orlistat three times daily do not significantly alter the bioavailability of a single 60-mg oral dose of nifedipine GITS in healthy volunteers.

The effect of orlistat, an inhibitor of dietary fat absorption, on the pharmacokinetics of beta-carotene in healthy volunteers

To assess the influence of orlistat, a lipase inhibitor, on the absorption of beta-carotene, an open-label, parallel, placebo-controlled, randomized, two-way crossover study was performed in 48 healthy volunteers between the ages of 19 and 58 years. Each subject received a single oral dose of 0, 30, 60, or 120 mg beta-carotene (12 subjects per dose level) on the fourth day of treatment with orlistat (120 mg) or placebo 3 times a day for 6 days. The treatments were separated by a washout period of at least 5 weeks. Serial blood samples were collected before and at appropriate intervals after administration of beta-carotene to determine plasma concentrations of unchanged beta-carotene. Short-term (3 to 6 days) treatment with orlistat did not alter endogenous profiles of beta-carotene in plasma. When beta-carotene was given during orlistat treatment, its absorption was reduced by approximately one-third. This reduction was consistent for all three dose levels of beta-carotene studied; however, the results for the 30-mg dose level were subject to greater variability, particularly for area under the concentration-time curve (AUC). It was concluded that two thirds of a supplemental dose of beta-carotene will be absorbed during orlistat treatment; this may be sufficient to achieve physiologic levels of beta-carotene with an appropriate dose of beta-carotene, should supplementation be needed in obese patients who have developed beta-carotene deficiency during therapy with orlistat.

Review of limited systemic absorption of orlistat, a lipase inhibitor, in healthy human volunteers

Orlistat, a lipase inhibitor, acts locally in the gastrointestinal tract. Systemic absorption is not required for its efficacy, but knowledge of the extent of its systemic absorption is important for its safe use in obese patients, the intended target population. Pharmacokinetic screening was carried out by monitoring plasma concentrations of unchanged orlistat in 25 phase 1 studies (including two mass balance studies) in normal and obese healthy volunteers. The results of these studies indicate an extremely low degree of systemic absorption for orlistat when administered with a hypocaloric, well-balanced diet with 20% to 30% of calories derived from fat (50-80 gm). To further characterize the pharmacokinetics and excretion pathways of orlistat, two mass balance studies using 14C-labeled orlistat were conducted. After oral dosing of radiolabeled orlistat with a fatty meal (28-30 gm fat), almost the entire dose was recovered from fecal samples; little was found in plasma and urine. It is concluded that systemic absorption of orlistat is negligible; at a clinically efficacious dose level, orlistat is unlikely to produce systemic lipase inhibition.

The influence of reduced dietary fat absorption induced by orlistat on the pharmacokinetics of digoxin in healthy volunteers

To assess the influence of an orlistat-induced reduction in dietary fat absorption on the pharmacokinetics of digoxin, an open-label, placebo-controlled, randomized, two-way crossover study was performed in 12 healthy volunteers. Each subject received single 0.4-mg doses of digoxin (soft gelatin capsules) administered orally on the fourth day of orlistat (120 mg three times daily for 6 days) and placebo (three times daily for 6 days) treatment, separated by at least an 11-day washout period. Serial blood samples were collected before and at appropriate intervals after each digoxin dose to determine plasma concentrations of unchanged digoxin. The 90% confidence intervals for the ratio of geometric least-squares means (for Cmax, AUC0-48, AUC0-t, and AUC) and for the difference of arithmetic least-squares means (for tmax and lambda z) indicate that the pharmacokinetics of digoxin was not altered by treatment with orlistat. This results suggests that a approximately 30% reduction in dietary fat absorption will not change the efficacy of digoxin in cardiac patients.

The influence of orlistat on the pharmacokinetics and pharmacodynamics of glyburide in healthy volunteers

To assess the influence of orlistat on the pharmacokinetics and pharmacodynamics (the blood glucose-lowering effect) of glyburide, an open-label, placebo-controlled, randomized, two-way crossover study was done in 12 healthy male volunteers. Each subject received single 5-mg oral doses of glyburide (Micronase; The Upjohn Company, Kalamazoo, MI) on the fifth day of treatment with placebo (treatment A) and 80-mg orlistat (treatment B) three times a day for 4 1/3 days; the two treatments were separated by a five-day washout period. Serial blood samples were collected before and at appropriate intervals after each glyburide dose to determine plasma concentrations and blood glucose levels. Values of Cmax and AUC of glyburide showed an equality of the two treatments by the analysis of variance. There was an apparent correlation between blood glucose level and the logarithm of plasma glyburide concentration; this relationship appeared to not be altered when glyburide was administered with orlistat. In conclusion, orlistat administered at doses of 80-mg three times daily does not significantly alter the pharmacokinetics and blood glucose-lowering effect of a single 5-mg oral dose of glyburide in healthy volunteers.