Determination of rofecoxib in human plasma and breast milk by high-performance liquid chromatographic assay

Chromatographic techniques in analysis of cyclooxygenase-2 inhibitors in drugs and biological samples

Non-steroidal anti-inflammatory drugs, as a therapeutic class, are among the most often used active pharmaceutical ingredients in heath care in the world. They are mostly available without prescription and often used for treatment of fever and pain. An extensive research of the literature published in analytical and pharmaceutical chemistry journals has been conducted and the chromatographic methods which were used for the purity, stability and pharmacokinetic studies of the cyclooxygenase-2 inhibitors, in formulations and biological materials have been reviewed. The methodology for the analysis of selected drugs is very well documented and many examples are available in the literature. The common use of chromatographic techniques with various detection attachments provide possibility for monitoring of drugs in therapy.

Transfer of rofecoxib into human milk

OBJECTIVE

To determine the milk-to-plasma (M/P) concentration ratio of rofecoxib in lactating mothers and estimate likely infant exposure.

METHODS

Rofecoxib 25 mg was given to six lactating women at weaning. Blood and milk were sampled up to 72 h post-dose for determination of rofecoxib concentrations. M/P ratios were derived from the respective area under the concentration-time curves. The infant 'dose' in milk was estimated and expressed as a percentage of the maternal dose, corrected for weight.

RESULTS

The median (range) M/P ratio and infant 'dose' were 0.25 (0.16-0.32) and 2.1% (1.8-3.2%), respectively.

CONCLUSIONS

The use of rofecoxib during breastfeeding is unlikely to pose harm to the suckling infant on the basis of low transfer into human milk.

Pre-column derivatization of rofecoxib for determination in serum by HPLC

An HPLC method for determination of rofecoxib in human serum is presented. The method is based on pre-column derivatization of analyte to a phenanthrene derivative of the drug. Rofecoxib and the internal standard were extracted from serum using liquid-liquid extraction. Upon exposure to UV light, the drug was found to undergo a photocyclization reaction, giving a species with high absorbance. Validation of the method has been studied in the concentration range 10-500 ng ml(-1).