Effect of prucalopride on the pharmacokinetics of oral contraceptives in healthy women.

BACKGROUND: Prucalopride is a selective, high-affinity, 5-hydroxytryptamine 4 (5-HT4) receptor agonist, which is approved for the symptomatic treatment of chronic constipation in women in whom laxatives fail to provide adequate relief. Women of childbearing potential, many of whom will be using oral contraceptives, comprise a large proportion of patients seeking medical therapy for constipation. OBJECTIVE: The aim of this study was to evaluate the effect of prucalopride on the absorption and steady-state pharmacokinetics of oral contraceptives in healthy women. METHODS: Sixteen women (aged 18-45 years) were enrolled in this open-label, two-way crossover trial (ClinicalTrials.gov identifier: NCT01036893) and given two 5-day treatments with a once-daily oral contraceptive (ethinylestradiol 0.035 mg + norethisterone 1 mg), alone and in combination with prucalopride 2 mg once daily. Treatments were separated by a 7 ± 2-day washout period. On days 1 and 5, blood samples were obtained pre-dose and at regular intervals post-dose up to 24 and 48 hours, respectively, to determine ethinylestradiol and norethisterone plasma concentrations. Prucalopride plasma concentrations were determined pre-dose and 3 hours post-dose on days 1 and 5, and 24 hours post-dose on day 6. Safety was assessed. RESULTS: Thirteen participants completed the study. One participant was thought to be non-compliant on days 3 and/or 4, and was excluded from the day 5 analysis. On days 1 and 5, maximum plasma concentrations of both oral contraceptive constituents were attained in ~1 hour and were unaffected by prucalopride administration. On day 5, steady-state prucalopride and oral contraceptive concentrations had been achieved. Prucalopride did not affect the pharmacokinetics of the oral contraceptives: point estimates for the maximum plasma concentration and area under the plasma concentration-time curve values and their associated 90 % confidence intervals were contained within predefined equivalence limits (80-125 %). Prucalopride was well tolerated, with a safety profile consistent with those observed in previous studies. CONCLUSION: Co-administration of prucalopride with an oral contraceptive did not result in any clinically meaningful pharmacokinetic interactions and was well tolerated.

Recommendations on bioanalytical method stability implications of co-administered and co-formulated drugs by Global CRO Council for Bioanalysis (GCC).

An open letter written by the Global CRO Council for Bioanalysis (GCC) describing the GCC survey results on stability data from co-administered and co-formulated drugs was sent to multiple regulatory authorities on 14 December 2011. This letter and further discussions at different GCC meetings led to subsequent recommendations on this topic of widespread interest within the bioanalytical community over the past 2 years.

Differential Rho-kinase dependency of full and partial muscarinic receptor agonists in airway smooth muscle contraction.

In airway smooth muscle (ASM), full and partial muscarinic receptor agonists have been described to have large differences in their ability to induce signal transduction, including Ca2+-mobilization. Despite these differences, partial agonists are capable of inducing a submaximal to maximal ASM contraction. To further elucidate transductional differences between full and partial muscarinic receptor agonists, we investigated the contribution of Rho-kinase (an important regulator of Ca2+-sensitization) to methacholine-, pilocarpine- and McN-A-343-induced bovine tracheal smooth muscle (BTSM) contraction, using the selective Rho-kinase inhibitor Y-27632. In addition, we measured Ca2+-mobilization and -influx in BTSM cells in response to these agonists in the absence and presence of Y-27632. Whereas treatment with Y-27632 (1 microM) significantly decreased potency (pEC50) for all agonists, maximal contraction (Emax) was reduced by 23.4+/-2.8 and 50.4+/-7.9% for the partial agonists pilocarpine and McN-A-343, respectively, but was unaffected for the full agonist methacholine. However, Emax of methacholine became Rho-kinase dependent after taking away its receptor reserve using the irreversible muscarinic receptor antagonist propylbenzilylcholine mustard. Pilocarpine and McN-A-343 induced a very small Ca2+-mobilization and -influx as compared to methacholine. In addition, an inverse relationship of these two parameters with the Rho-kinase dependency was observed. Interestingly, no inhibitory effects of Y-27632 were observed on Ca2+-mobilization and-influx for all three agonists, indicating that the effects of Y-27632 on contraction are most likely on the level of Ca2+-sensitization. In conclusion, in contrast to the full agonist methacholine, the partial muscarinic receptor agonists pilocarpine and McN-A-343 are dependent on Rho-kinase for their maximal contractile effects, presumably as a consequence of differences in transductional reserve, indicating an agonist-dependent role for Rho-kinase in ASM contraction. Moreover, an inverse relationship exists between Rho-kinase dependency and both Ca2+-mobilization and Ca2+-influx for these agonists.

Protein kinase C potentiates homologous desensitization of the beta2-adrenoceptor in bovine tracheal smooth muscle.

Preincubation (30 min) of bovine tracheal smooth muscle with various concentrations (0.1, 1 and 10 microM) of fenoterol decreased isoprenaline-induced maximal relaxation (E(max)) of methacholine-contracted preparations in a concentration dependent fashion, indicating desensitization of the beta(2)-adrenoceptor. Preincubation with 1 microM of the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) caused a small but significant decrease in isoprenaline-induced E(max), indicating activated PKC-mediated heterologous beta(2)-adrenoceptor desensitization. To investigate the capacity of activated PKC to regulate homologous desensitization, we incubated the smooth muscle strips with the combination of both 1 microM PMA and 1 microM fenoterol. This combined treatment synergistically decreased the isoprenaline-induced maximal relaxation, as compared to the individual effects of PMA and fenoterol alone, indicating a common pathway for heterologous and homologous desensitization. Moreover, the specific PKC-inhibitor 2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl) maleimide (GF 109203X) markedly increased the potency and E(max) of isoprenaline for all conditions used, including control conditions, and the synergistic effects of PMA and fenoterol were completely prevented. In conclusion, the present study demonstrates that homologous desensitization of the beta(2)-adrenergic receptor can be enhanced by PKC activation. For the first time we have provided evidence that this concept is functionally operative in airway smooth muscle, and it may explain the reduced bronchodilator response to beta(2)-adrenoceptor agonists in patients with asthma during a severe exacerbation.

Potentiation of beta-adrenoceptor function in bovine tracheal smooth muscle by inhibition of protein kinase C.

To examine the role of contractile agonist-induced activation of protein kinase C (PKC) in functional antagonism of airway smooth muscle contraction by beta-adrenoceptor agonists, we examined the effects of the specific PKC-inhibitor GF 109203X (2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl) maleimide) on isoprenaline-induced relaxation of bovine tracheal smooth muscle contracted by various concentrations of methacholine and histamine. In the absence of GF 109203X, the potency of isoprenaline (pD(2)) was gradually reduced at increasing methacholine- and histamine-induced smooth muscle tones, but the maximal relaxation (E(max)) was decreased only at higher concentrations of methacholine. In the presence of GF 109203X, pD(2) values were significantly increased for both methacholine- and histamine-induced contractions. Moreover, isoprenaline E(max) values in the presence of high concentrations of methacholine were also increased. Although both methacholine- and histamine-induced contractions were slightly reduced by GF 109203X, the changes in isoprenaline pD(2) could only partially be explained by reduced contractile tone. In contrast to isoprenaline, forskolin-induced relaxations were not affected by GF 109203X. The results indicate that PKC activation contributes to the reduced beta-adrenergic responsiveness induced by methacholine and histamine, which may involve uncoupling of the beta-adrenoceptor from the effector system. Since many mediators and neurotransmitters in allergic airway inflammation can activate PKC, this cross talk may be important in the reduced bronchodilator response of patients with severe asthma.