Pharmacokinetics of intravenous and oral midazolam in plasma and saliva in humans: usefulness of saliva as matrix for CYP3A phenotyping.

AIMS: To compare midazolam kinetics between plasma and saliva and to find out whether saliva is suitable for CYP3A phenotyping. METHODS: This was a two way cross-over study in eight subjects treated with 2 mg midazolam IV or 7.5 mg orally under basal conditions and after CYP3A induction with rifampicin. RESULTS: Under basal conditions and IV administration, midazolam and 1'-hydroxymidazolam (plasma, saliva), 4-hydroxymidazolam and 1'-hydroxymidazolam-glucuronide (plasma) were detectable. After rifampicin, the AUC of midazolam [mean differences plasma 53.7 (95% CI 4.6, 102.9) and saliva 0.83 (95% CI 0.52, 1.14) ng ml(-1) h] and 1'-hydroxymidazolam [mean difference plasma 11.8 (95% CI 7.9 , 15.7) ng ml(-1) h] had decreased significantly. There was a significant correlation between the midazolam concentrations in plasma and saliva (basal conditions: r = 0.864, P < 0.0001; after rifampicin: r = 0.842, P < 0.0001). After oral administration and basal conditions, midazolam, 1'-hydroxymidazolam and 4-hydroxymidazolam were detectable in plasma and saliva. After treatment with rifampicin, the AUC of midazolam [mean difference plasma 104.5 (95% CI 74.1, 134.9) ng ml(-1) h] and 1'-hydroxymidazolam [mean differences plasma 51.9 (95% CI 34.8, 69.1) and saliva 2.3 (95% CI 1.9, 2.7) ng ml(-1) h] had decreased significantly. The parameters separating best between basal conditions and post-rifampicin were: (1'-hydroxymidazolam + 1'-hydroxymidazolam-glucuronide)/midazolam at 20-30 min (plasma) and the AUC of midazolam (saliva) after IV, and the AUC of midazolam (plasma) and of 1'-hydroxymidazolam (plasma and saliva) after oral administration. CONCLUSIONS: Saliva appears to be a suitable matrix for non-invasive CYP3A phenotyping using midazolam as a probe drug, but sensitive analytical methods are required.

Pharmacokinetics and pharmacodynamics of sildenafil in a patient treated with human immunodeficiency virus protease inhibitors.

We describe a 44-year-old male patient with human immunodeficiency virus (HIV) infection and pulmonary arterial hypertension who was treated with several protease inhibitors and with sildenafil. In order to guide treatment with sildenafil, the pharmacokinetics and dynamics of sildenafil were monitored at various time points. In comparison with healthy subjects, the maximal concentration in plasma (Cmax), area under the curve (AUC), and elimination half-life of sildenafil were approximately doubled in the patient. After increasing the sildenafil dose to ensure therapeutic drug levels over 24 hours, the pulmonary arterial hypertension and physical performance of the patient improved significantly. We conclude that the elimination of sildenafil is impaired in patients treated with protease inhibitors, but to a lesser extent than predicted from single-dose studies reported in the literature. Patients treated concomitantly with protease inhibitors and sildenafil need close monitoring of plasma levels, pharmacodynamics, and toxicity of sildenafil in order to be treated optimally.