Issues in contemporary drug delivery. Part VI: Advanced cardiac drug formulations

Population pharmacokinetic analysis for hydrocodone following the administration of hydrocodone bitartrate extended-release capsules

BACKGROUND AND OBJECTIVE

Hydrocodone is a semi-synthetic narcotic analgesic and antitussive. Although hydrocodone products have been on the market for over 50 years, relatively little is known about its pharmacokinetics. Additionally, there are no published reports of population pharmacokinetic analyses for hydrocodone. Furthermore, current labeling of hydrocodone-containing products provides little guidance in terms of the impact of patient descriptors on the pharmacokinetics of hydrocodone. The objectives of this analysis were to develop a population pharmacokinetic model that characterizes the pharmacokinetics of hydrocodone following single and multiple oral doses of hydrocodone extended-release capsules (hydrocodone bitartrate ER capsules) in healthy subjects and patients, to examine the impact of patient descriptors on pharmacokinetic parameters and to assess the dose-proportionality of hydrocodone pharmacokinetic.

METHODS

A total of 4,714 plasma hydrocodone concentrations from 220 subjects were available for this analysis. The data were extracted from seven studies (five phase 1 and two phase 2 studies). A two-compartment open mamillary model with linear elimination and a complex absorption model was used to fit the data, using NONMEM(®) version 7.1.2 software. The absorption model involved two sequential first-order absorption processes with the delay in the first process accomplished by means of multiple transit compartments. Covariate analysis was performed using standard forward selection followed by backward elimination processes. Model evaluation was performed using a prediction-corrected visual predictive check (pcVPC).

RESULTS

The population estimates of apparent oral central volume of distribution and apparent oral linear clearance were 714 L and 64.4 L/h, respectively. The first absorption process was rapid. Creatinine clearance and body surface area (BSA) were statistically significant predictors of the apparent oral clearance and apparent oral volume of distribution. The pcVPC indicated that the model provided a robust and unbiased fit to the data.

CONCLUSIONS

A linear model for hydrocodone elimination provided an adequate fit to the observed data over the entire dose range, which supports that hydrocodone bitartrate ER capsules exhibit dose-proportional pharmacokinetics. The formulation of hydrocodone bitartrate ER capsules results in absorption profiles that are variable across and within subjects. Despite the variability in absorption profiles, a relatively simple model provided an adequate fit to the data. Creatinine clearance and BSA were statistically significant predictors of the apparent oral clearance and apparent oral volume of distribution. Absorption characteristics of hydrocodone bitartrate ER capsules should still allow effective plasma concentrations of hydrocodone to be reached quickly and for effective concentrations to be maintained for a long period.

Advanced and controlled drug delivery systems in clinical disease management

Advanced and controlled drug delivery systems are important for clinical disease management. In this review the most important new systems which have reached clinical application are highlighted. Microbiologically controlled drug delivery is important for gastrointestinal diseases like ulcerative colitis and distally localized Crohn's disease. In cardiology the more classic controlled release systems have improved patient compliance and decreased side effects. In the treatment of intractable pain the spinal and transdermal route is well documented. In neurology the flattened peak-through levels of antiepileptic drugs and anti Parkinson's drugs represents a more predictable kinetic profile. Tracheal delivery of corticosteroids and sympaticomimetics in asthma and Chronic Obstructive Pulmonary Disease is fully accepted in clinical practice: delivery by this route results in better efficacy and a better safety profile. In gynaecology the delivery of pulsatile hormones (LHRH) is used for pregnancy induction, while transdermal oestrogens are promising in the prevention of osteoporosis. In surgical practice the use of antibiotic impregnated bone cement and antibiotic impregnated biodegradable collagens is well established. To prevent infections intravascular catheters coated with heparin or antibiotics are used. In ophthalmology the Ocusert systems provide a controlled release of different drugs in the eye. Most spectacular is the clinical introduction of the first liposomal drugs; amfotericine B and daunorubicine. Liposomal formulations of these drugs have enhanced activity and decreased toxicity compared to conventional formulations.

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