Lack of a pharmacokinetic interaction between treprostinil diolamine and sildenafil in healthy adult volunteers.

Treprostinil, a stable prostacyclin analogue used in the treatment of pulmonary arterial hypertension, is in development as a sustained release oral tablet, treprostinil diolamine (United Therapeutics Corp, Research Triangle Park, NC). As combination therapy yields additional benefit in pulmonary arterial hypertension, treprostinil diolamine may be used with sildenafil, a phosphodiesterase-5 inhibitor. This study was designed to evaluate the presence of a pharmacokinetic drug interaction between treprostinil diolamine and sildenafil. Treprostinil is primarily metabolized by cytochrome (CYP) P450 2C8 with minor contribution from CYP2C9. Sildenafil is metabolized by CYP3A4 with minor contribution from CYP2C9. Eighteen healthy volunteers were randomized to receive 4.5 days each of (1) treprostinil diolamine alone, (2) sildenafil alone, and (3) combination treprostinil diolamine and sildenafil in an open-label, 3-period, 3-sequence crossover study. The geometric mean ratio (90% confidence intervals) for combination/agent alone of steady state area under the concentration-time curve and peak concentration (Cmax) were 0.972 (0.824-1.145) and 1.030 (0.900, 1.1-9), respectively, for treprostinil diolamine and were 0.881 (0.804-0.966) and 0.910 (0.876-0.946), respectively, for sildenafil. The results suggest lack of a metabolic interaction between treprostinil diolamine and sildenafil, as geometric mean ratio 90% confidence intervals were within 0.8-1.25. Combination therapy was well tolerated but had slightly higher rates of nausea, headache, and extremity pain than monotherapy.

Treatment satisfaction is associated with improved quality of life in patients treated with inhaled treprostinil for pulmonary arterial hypertension.

BACKGROUND: Patient treatment satisfaction is likely to be a highly relevant outcome measure in pulmonary arterial hypertension (PAH), a condition for which the benefits of treatment must be weighed against frequent, undesirable side effects, inconvenience, and complications associated with therapy. In this study, we sought to evaluate the psychometric properties of a patient-reported treatment satisfaction measure and its relationship to quality of life (QoL) among patients transitioning from inhaled iloprost (iILO) to inhaled treprostinil (iTRE). METHODS: We studied treatment satisfaction among 66 subjects with PAH in a single-arm, open-label, multi-center trial of iTRE following transition from iILO. Treatment satisfaction was assessed using the Treatment Satisfaction Questionnaire for Medication (TSQM, version 1.4) administered to subjects immediately before and 12 weeks after transition of inhaled therapy. The TSQM is comprised of 4 domains: effectiveness, side effects, convenience, and global satisfaction. Scores range from 0 to 100 with higher scores indicating greater satisfaction. Six-minute walk distance (6MWD), functional class, adverse events, drug administration time, and PAH-specific QoL (CAMPHOR) were concurrently assessed. RESULTS: Domains of the TSQM demonstrated evidence of strong internal consistency at baseline and at 12 weeks (Cronbach α = 0.88-0.93). Transition from iILO to iTRE was associated with an improvement in 3 of 4 TSQM domains: effectiveness (+20 ± 21, p < 0.0001), side effects (0 ± 22, p = 0.97), convenience (+39 ± 26, p < 0.0001), and global satisfaction (+20 ± 24, p = 0.0005). Change in effectiveness scores correlated with change in 6MWD (r = 0.43, p = 0.0004) and side effects scores at 12 weeks correlated inversely with number of severity-weighted treatment-emergent adverse events (r = -0.44, p = 0.0002). In multiple regression models adjusted for baseline characteristics, changes in effectiveness and convenience satisfaction scores were significantly associated with improvement in PAH-specific QoL (p = 0.002 and p = 0.01). CONCLUSIONS: The TSQM demonstrated acceptable performance characteristics in patients with PAH. Changes in treatment satisfaction resulting from transitioning from iILO to iTRE were associated with improvements in PAH-specific QoL.

Lack of a pharmacokinetic interaction between oral treprostinil and bosentan in healthy adult volunteers.

Treprostinil diethanolamine is an oral prostacyclin analog currently being evaluated for the treatment of pulmonary arterial hypertension (PAH). Treprostinil is metabolized primarily by cytochrome P450 (CYP) 2C8 with minor contribution from CYP2C9. It is expected that oral treprostinil will be administered with bosentan, approved for the treatment of PAH and known to induce CYP2C9 and 3A4. This study evaluated whether a drug interaction exists between oral treprostinil, bosentan, and its active metabolite Ro 48-5033 during co-administration. Twenty-four participants were randomized in a 3-way crossover study to oral treprostinil 1 mg twice daily, bosentan 125 mg twice daily, and oral treprostinil 1 mg twice daily and bosentan 125 mg twice daily. Treprostinil geometric mean ratios (GMRs) (90% confidence interval [CIs]) for steady-state AUC(0-12) and C(max) (combination/treprostinil) were 0.92 (0.83, 1.03) and 0.96 (0.83, 1.11), respectively, whereas bosentan GMRs (combination/bosentan) were 1.02 (0.95, 1.10) and 1.04 (0.94, 1.15), respectively, and Ro 48-5033 GMRs were 0.99 (0.93, 1.06) and 1.03 (0.94, 1.13). In conclusion, because the GMR and 90% CI are within the equivalence interval of 0.8 to 1.25, co-administration of oral treprostinil and bosentan did not result in a pharmacokinetic interaction for either agent.

Poor correlation between 6beta-hydroxycortisol:cortisol molar ratios and midazolam clearance as measure of hepatic CYP3A activity.

AIMS: A non-invasive proposed method for measuring CYP3A activity is the urinary 6beta-hydroxycortisol:cortisol ratio. This ratio has been used as an indicator of CYP3A induction and inhibition, with mixed results. This investigation evaluated the relationship between a validated, biomarker, intravenous midazolam clearance and the urinary cortisol ratio under constitutive conditions and with the influence of a moderate CYP3A inhibitor. METHODS: This was a sequential, cross-over study design. Intravenous midazolam 0.025 mg kg(-1) was administered to 10 male and 10 female subjects once every 14 days for 4 months. Fluvoxamine 150 mg day(-1) was given to all subjects during the last two visits. Total body clearance of midazolam and urinary 6beta-hydroxycortisol:cortisol molar ratio were used as biomarkers of hepatic CYP3A activity. RESULTS: No significant correlations were found between these two markers (r(2) < 0.5, P > 0.05). Larger interindividual and intra-individual variability in CYP3A activity was observed in 6beta-hydroxycortisol:cortisol ratios compared with midazolam clearances. With fluvoxamine therapy, midazolam clearance values decreased approximately 1.5-fold and cortisol ratios decreased approximately 1.9-fold. CONCLUSIONS: The high intra-individual variability of the urinary cortisol ratio, compared with midazolam, makes this a suboptimal CYP3A phenotyping tool.

Pharmacokinetic and pharmacodynamic investigation of efavirenz in the semen and blood of human immunodeficiency virus type 1-infected men.

Therapeutic concentrations of antiretroviral agents in seminal plasma (SP) may reduce virus burden and influence sexual transmission of human immunodeficiency virus (HIV) type 1. This study compared the pharmacokinetic, pharmacodynamic, and dose responses of efavirenz (EFV) in SP versus those in blood plasma (BP). A total of 431 BP samples and 157 SP samples were obtained over a period of 40 days, from 9 EFV-naive men (i.e., men about to receive EFV for the first time) and from 12 EFV-experienced men (i.e., men already receiving EFV as part of an antiretroviral regimen). Overall, median EFV exposure in SP was 3.4% (range, 2.0%-5.0%) of that in BP. However, all EFV concentrations in SP were >/=40-fold higher than the wild-type IC(90) (IC(90)(WT)) for HIV-1. During the dosing interval, no single SPrcolon;BP EFV-concentration ratio was significantly predictive of the absolute measure of exposure in SP. By day 40, HIV-1 RNA in SP was undetectable in 8 (89%) of 9 EFV-naive men and remained undetectable in 10 (83%) of 12 EFV-experienced men. In SP, EFV reaches concentrations above the HIV-1 IC(90)(WT) throughout the dosing interval. EFV-containing regimens effectively suppress HIV-1 RNA in SP.