Similar rivastigmine pharmacokinetics and pharmacodynamics in Japanese and white healthy participants following the application of novel rivastigmine patch.

The pharmacokinetics and pharmacodynamics of rivastigmine were compared in Japanese and white healthy participants who were given ascending single doses of the novel rivastigmine transdermal patch. Rivastigmine patch strengths were 4.6 mg/24 h (5 cm2, 9 mg rivastigmine loaded dose), 9.5 mg/24 h (10 cm2, 18 mg), and 13.3 mg/24 h (15 cm2, 27 mg) (per label) or 7.0 mg/24 h (7.5 cm2, 13.5 mg) as a fall-back dose. No relevant ethnic differences in the noncompartmental pharmacokinetics (parent and metabolite NAP226-90) and pharmacodynamics (plasma BuChE activity) of the rivastigmine patch were observed between Japanese and whites. However, drug exposure was slightly higher and inhibition of BuChE slightly more pronounced in Japanese participants than in whites, which was attributed to the lower body weight (ca. 11% less on average) of Japanese participants. Treatments were similarly well tolerated in both ethnic groups. In conclusion, no relevant ethnic differences in the intrinsic disposition or effects of rivastigmine delivered via transdermal route are expected between Japanese and white patients. The possible effect of body weight on drug exposure suggests that special attention should be paid to patients with very low body weight during up-titration.

Simultaneous determination of metronidazole and spiramycin I in human plasma, saliva and gingival crevicular fluid by LC-MS/MS.

An analytical validation of a new liquid chromatographic-mass spectrometric (LC-MS/MS) method for simultaneous determination of metronidazole and spiramycin I concentrations in human plasma, saliva and gingival crevicular fluid (GCF) is presented. Ornidazole was used as an internal standard, and sample pre-treatment consisted of a liquid-liquid extraction. Chromatographic separation was achieved on a 5 microm Kromasil C18 column (150 mm x 4.6 mm i.d., particle size 5 microm), with a gradient using acetonitrile, water and formic acid at a flow rate of 0.9 ml/min. The methods were validated in terms of intra- and inter-batch precision (<7.1% in plasma, 12% in saliva and 9.2% in GCF, respectively) and accuracy (within +/-8.7% in plasma, within +/-8.7%, except LDQ level within +/-15.4% in saliva and within +/-10.7% in GCF), linearity, specificity, recovery (extraction efficiency), matrix effect, dilution process, stability in human plasma and saliva after three freeze-thaw cycles, stability in human plasma and saliva at ambient temperature and stability of the extracts in the automatic injector of the HPLC system. The methods are applicable for accurate and simultaneous monitoring of the plasma, saliva and gingival crevicular fluid levels of metronidazole and spiramycin I from pharmacokinetic studies.