Effects of orlistat, a lipase inhibitor, on the pharmacokinetics of three highly lipophilic drugs (amiodarone, fluoxetine, and simvastatin) in healthy volunteers

To investigate the effect of orlistat on the pharmacokinetics of three highly lipophilic drugs (amiodarone, fluoxetine, and simvastatin), the authors performed double-blind, placebo-controlled, randomized two-period crossover (for fluoxetine and simvastatin) or parallel (for amiodarone) studies in healthy volunteers ages 18 to 65 years of a body mass index between 18 and 30 kg/m2. During treatment with orlistat or matching placebo for 5 to 13 1/3 days, a single oral dose of highly lipophilic drug was administered, followed by obtaining serial blood samples for measuring plasma (for fluoxetine and simvastatin) or serum (for amiodarone) concentrations of the lipophilic drug and its active metabolite. Treatments were compared for the pharmacokinetic parameters AUC0-infinity, Cmax, tmax, and t 1/2 of highly lipophilic drugs and active metabolites. Analysis of variance was performed to assess the significance of the sequence effect and provide the variance estimate for the 90% confidence intervals. Subjects were also evaluated for adverse events, vital signs, and clinical and laboratory safety. The absorption of amiodarone (and active metabolite) was significantly reduced by approximately one-quarter using parameters of Cmax and AUC, while no inhibition of absorption was observed for fluoxetine and simvastatin as well as their active metabolites. There were no clinically significant differences in t 1/2 and tmax for all three drugs tested. Due to expected gastrointestinal adverse events known to occur with orlistat, there was a higher incidence of adverse events under regimen B (highly lipophilic drugs and orlistat) than under regimen A (highly lipophilic drugs and placebo). Other adverse events were sporadic and unremarkable. There were no clinically relevant changes in vital signs or laboratory values. In conclusion, except for amiodarone, there was no effect of orlistat on the pharmacokinetics of highly lipophilic drugs when these drugs were taken concomitantly with orlistat.

Cerivastatin: a review of its pharmacological properties and therapeutic efficacy in the management of hypercholesterolaemia

Cerivastatin is an HMG-CoA reductase inhibitor used for the treatment of patients with hypercholesterolaemia. The lipid-lowering efficacy of cerivastatin has been demonstrated in a number of large multicentre, randomised clinical trials. Earlier studies used cerivastatin at relatively low dosages of < or =0.3mg orally once daily, but more recent studies have focused on dosages of 0.4 or 0.8 mg/day currently recommended by the US Food and Drug Administration (FDA). Along with modest improvements in serum levels of triglycerides and high density lipoprotein (HDL)-cholesterol, cerivastatin 0.4 to 0.8 mg/day achieved marked reductions in serum levels of low density lipoprotein (LDL)-cholesterol (33.4 to 44.0%) and total cholesterol (23.0 to 30.8%). These ranges included results of a pivotal North American trial in almost 1000 patients with hypercholesterolaemia. In this 8-week study, US National Cholesterol Education Program (Adult Treatment Panel II) [NCEP] target levels for LDL-cholesterol were achieved in 84% of patients randomised to receive cerivastatin 0.8 mg/day, 73% of those treated with cerivastatin 0.4 mg/day and <10% of placebo recipients. Among patients with baseline serum LDL-cholesterol levels meeting NCEP guidelines for starting pharmacotherapy, 75% achieved target LDL-cholesterol levels with cerivastatin 0.8 mg/day. In 90% of all patients receiving cerivastatin 0.8 mg/day, LDL-cholesterol levels were reduced by 23.9 to 58.4% (6th to 95th percentile). Various subanalyses of clinical trials with cerivastatin indicate that the greatest lipid-lowering response can be expected in women and elderly patients. Cerivastatin is generally well tolerated and adverse events have usually been mild and transient. The overall incidence and nature of adverse events reported with cerivastatin in clinical trials was similar to that of placebo. The most frequent adverse events associated with cerivastatin were headache, GI disturbances, asthenia, pharyngitis and rhinitis. In the large pivotal trial, significant elevations in serum levels of creatine kinase and transaminases were reported in a small proportion of patients receiving cerivastatin but not in placebo recipients. As with other HMG-CoA reductase inhibitors, rare reports of myopathy and rhabdomyolysis have occurred with cerivastatin, although gemfibrozil or cyclosporin were administered concomitantly in most cases. Postmarketing surveillance studies in the US have been performed. In 3 mandated formulary switch conversion studies, cerivastatin was either equivalent or superior to other HMG-CoA reductase inhibitors, including atorvastatin, in reducing serum LDL-cholesterol levels or achieving NCEP target levels. Pharmacoeconomic data with cerivastatin are limited, but analyses conducted to date in the US and Italy suggest that cerivastatin compares favourably with other available HMG-CoA reductase inhibitors in terms of its cost per life-year gained.

CONCLUSION

Cerivastatin is a well tolerated and effective lipid-lowering agent for patients with hypercholesterolaemia. When given at dosages currently recommended by the FDA in the US, cerivastatin achieves marked reductions in serum levels of LDL-cholesterol, reaching NCEP target levels in the vast majority of patients. Thus, cerivastatin provides a useful (and potentially cost effective) alternative to other currently available HMG-CoA reductase inhibitors as a first-line agent for hypercholesterolaemia.

Clinical pharmacokinetics of cerivastatin

Cerivastatin sodium, a novel statin, is a synthetic, enantiomerically pure, pyridine derivative that effectively reduces serum cholesterol levels at microgram doses. Cerivastatin is readily and completely absorbed from the gastrointestinal tract, with plasma concentrations reaching a peak 2 to 3 hours postadministration followed by a monoexponential decay with an elimination half-life (t1/2beta) of 2 to 3 hours. Cerivastatin pharmacokinetics are linear: maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) are proportional to the dose over the range of 0.05 to 0.8 mg. No accumulation is observed on repeated administration. Cerivastatin interindividual variability is described by coefficients of variation of approximately 30 to 40% for its primary pharmacokinetic parameters AUC, Cmax and t1/2beta. The mean absolute oral bioavailability of cerivastatin is 60% because of presystemic first-pass effects. Its pharmacokinetics are not influenced by concomitant administration of food nor by the time of day at which the dose is given. Age, gender, ethnicity and concurrent disease also have no clinically significant effects. Cerivastatin is highly bound to plasma proteins (>99%). The volume of distribution at steady state of about 0.3 L/kg indicates that the drug penetrates only moderately into tissue; conversely, preclinical studies have shown a high affinity for liver tissue, the target site of action. Cerivastatin is exclusively cleared via metabolism. No unchanged drug is excreted. Cerivastatin is subject to 2 main oxidative biotransformation reactions: demethylation of the benzylic methyl ether moiety leading to the metabolite M-1 [catalysed by cytochrome P450 (CYP) 2C8 and CYP3A4] and stereoselective hydroxylation of one methyl group of the 6-isopropyl substituent leading to the metabolite M-23 (catalysed by CYP2C8). The product of the combined biotransformation reactions is a secondary minor metabolite, M-24, not detectable in plasma. All 3 metabolites are active inhibitors of hydroxymethylglutaryl-coenzyme A reductase with a similar potency to the parent drug. Approximately 70% of the administered dose is excreted as metabolites in the faeces, and 30% in the urine. Metabolism by 2 distinct CYP isoforms renders cerivastatin relatively resistant to interactions arising from inhibition of CYP. If one of the pathways is blocked, cerivastatin can be effectively metabolised by the alternative route. In addition, on the basis of in vitro investigations, there is no evidence for either cerivastatin or its metabolites having any inducing or inhibitory activity on CYP. The apparent lack of any clinically relevant interactions with a variety of drugs commonly used by patients in the target population supports this favourable drug-drug interaction profile.