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Clin Pharmacokinet. 2001;40(5):375-82.

Application of a gamma model of absorption to oral cyclosporin.

Author information

1
Service de Pharmacologie-Toxicologie, Hĵpital Dupuytren, Limoges, France. debord@unilim.fr

Abstract

BACKGROUND:

Some drugs, such as cyclosporin, exhibit flat and delayed absorption profiles, with a correlation between the delay and the peak width. Such profiles can be described by an absorption model in which the absorption rate is derived from a gamma distribution (of which the classical first-order absorption model is a special case).

OBJECTIVE:

To develop a model for the pharmacokinetics of extravascular administration of cyclosporin and apply it to a study of the pharmacokinetics of cyclosporin microemulsion in stable renal transplant recipients.

PATIENTS AND PARTICIPANTS:

21 renal transplant patients receiving oral cyclosporin microemulsion 75 to 175 mg twice daily.

METHODS:

The equation of the plasma concentration-time curve after oral administration was expressed as a convolution product between the absorption rate and a multi-exponential impulse response. The convolution integral was computed analytically and expressed in terms of the incomplete gamma function. Cyclosporin was assayed by liquid chromatography/mass spectrophotometry. The model was fitted by nonlinear regression, using a specially developed program.

RESULTS:

The gamma model yielded a good fit in all of the 21 patients studied. Attempts to fit the same data by a classical exponential with lag-time model failed in most patients.

CONCLUSIONS:

This model could simplify the Bayesian monitoring of cyclosporin therapy.

[Indexed for MEDLINE]

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