Evaluation of pharmacokinetic interaction between cetirizine and ritonavir, an HIV-1 protease inhibitor, in healthy male volunteers.

BACKGROUND: Serious adverse effects have been observed with some non-sedative H1-antihistamines (terfenadine and astemizole) when they were associated with drugs known to inhibit their metabolism. However, this is not a class effect, and this interaction should be considered on a case-by-case basis. The aim of this study was to evaluate the potential of pharmacokinetic interaction between cetirizine and ritonavir, the most potent cytochrome P450 (CYP) inhibitor. METHODS: An open-label, single-center, one-sequence crossover pharmacokinetic study was conducted in three running periods: cetirizine (CTZ) alone, ritonavir (RTV) alone and then CTZ plus RTV. For each period, steady-state pharmacokinetics were obtained. RTV and CTZ plasma concentrations were determined using validated liquid chromatography methods. The statistical method was based on a 90% confidence interval (CI) for the ratio of population geometric means (combination/drug alone) for each drug and for each parameter [area under the plasma concentration versus time curve (AUC(0-tau,ss)), value of maximum plasma concentration (C(max,ss))] and compared to bioequivalence ranges 80-125% and 70-143% for AUC(0-tau,ss) and C(max,ss), respectively. RESULTS: Among the 17 male subjects enrolled (26.4 +/- 8.6 years), 16 completed the study (1 withdrawal after the first period). The RTV pharmacokinetic parameter values were not affected by CTZ co-treatment. With RTV, a 42% increase in the CTZ AUC(0-tau,ss) (3406 versus 4840 microgh/l, 90% CI of 128-158%), a 53% increase in the CTZ elimination half-life (7.8 h versus 11.9 h, P = 0.001), a slight increase (15%) in the CTZ apparent volume of distribution (V(d,ss)/f) (34.7 l versus 39.8 l, P = 0.035), a 29% decrease in the CTZ apparent total body clearance (49.9 ml/min versus 35.3 ml/min, P < 0.001) and bioequivalent C(max,ss) (374 microg/l versus 408 microg/l) were observed. No serious drug related adverse effects were notified. CONCLUSIONS: CTZ does not significantly affect the pharmacokinetic parameters of RTV, and the association does not, thus, require a modification of the dosage of the protease inhibitor. The increased extent of exposure to CTZ in healthy subjects, in the presence of RTV administered at high doses, remained in the same range as previously observed in the elderly or in mildly renally impaired subjects.

Effect of tumour necrosis factor alpha on rat blastocyst growth and glucose metabolism.

Tumour necrosis factor alpha (TNF-alpha) synthesis has recently been described in the uterus during the preimplantation phase of pregnancy. The present study was undertaken to determine whether preimplantation embryos are a potential target for TNF-alpha in rats. First, the expression of TNF-alpha receptors by blastocysts was demonstrated by ligand binding assay with human 125I-labelled TNF-alpha and reverse transcription-amplification for the p60 receptor form. The functionality of these receptors was then assessed by incubating blastocysts with 3 nmol mouse TNF-alpha l-1 in vitro and determining their morphology and the number of cells after 24 h. At that concentration, cell proliferation in blastocysts was inhibited by TNF-alpha but this was not accompanied by any change in the morphology of the embryos. Similar results were obtained when lower doses of TNF-alpha (30 and 300 pmol l-1) were tested. The rate of glucose consumption of rat blastocysts exposed to 3 nmol TNF-alpha l-1 was not altered when they were incubated with the cytokine for 4 h, but the rate of glucose incorporation decreased over the same period. Our data indicate that rat blastocysts are responsive to physiological concentration of TNF-alpha and that this cytokine has the potential to influence the preimplantation development of rats.