Absorption Of Fexofenadine Research Articles

Fexofenadine in horses: pharmacokinetics, pharmacodynamics and effect of ivermectin pretreatment

The pharmacokinetics and the effects on inhibition of histamine-induced cutaneous wheal formation of the histamine H1-antagonist fexofenadine were studied in horse. The effect of ivermectin pretreatment on the pharmacokinetics of fexofenadine was also examined. After intravenous infusion of fexofenadine at 0.7 mg/kg bw the mean terminal half-life was 2.4 h (range: 2.0-2.7 h), the apparent volume of distribution 0.8 L/kg (0.5-0.9 L/kg), and the total body clearance 0.8 L/h/kg (0.6-1.2 L/h/kg). After oral administration of fexofenadine at 10 mg/kg bw bioavailability was 2.6% (1.9-2.9%). Ivermectin pretreatment (0.2 mg/kg, p.o.) 12 h before oral fexofenadine decreased the bioavailability to 1.5% (1.4-2.1%). In addition, the area under the plasma concentration-time curve decreased 27%. Ivermectin did not affect the pharmacokinetics of i.v. administered fexofenadine. Ivermectin may influence fexofenadine absorption by interfering in intestinal efflux and influx pumps, such as P-glycoprotein and the organic anion transport polypeptide family. Oral and i.v. fexofenadine significantly decreased histamine-induced wheal formation, with a maximal duration of 6 h. A pharmacokinetic/pharmacodynamic link model indicated that fexofenadine in horse has antihistaminic effects at low plasma concentrations (EC50 = 16 ng/mL). However, oral treatments of horses with fexofenadine may not be suitable due to the low bioavailability.

Effect of erythromycin on the absorption of fexofenadine in the jejunum, ileum and colon determined using local intubation in healthy volunteers

To investigate the in vivo intestinal absorption mechanism(s) and systemic availability of fexofenadine in the jejunum, ileum and colon in humans. A single dose of fexofenadine hydrochloride (60 mg as solution) was applied under fasting conditions, either alone or directly after a solution of erythromycin lactobionate (corresponding to a dose of 250 mg erythromycin), to the jejunum, ileum and colon in 6 healthy volunteers (3 male and 3 female) using a regional intubation dosing technology (Bioperm AB, Lund, Sweden). A total of 36 fexofenadine administrations were performed. The administration of fexofenadine to the specified location either alone or in combination with erythromycin was conducted in a randomized manner on 2 consecutive days with a 5-day washout period between doses. The plasma AUC for fexofenadine (mean +/- SEM) was higher (2.7-to 2.3-fold, p < 0.001) after application to the jejunum (1090 +/- 134 h x ng/ml) than to the ileum (404 +/- 102 h x ng/ml) or colon (476 +/- 212 h x ng/ml). No significant differences were found between application to the ileum and colon. The administration of erythromycin affected the absorption rate after jejunal application with a prolonged tmax from a median of 40 min (range 10-90 min) to a median of 3 hours (range 10-180 min) (p = 0.009). A change in tmax was not observed with application to the ileum and colon. The concomitant administration of erythromycin in the jejunum tended to increase the plasma AUC of fexofenadine from 1090 +/- 134 to 1750 +/- 305 h x ng/ml (p = 0.069). The systemic availability of fexofenadine was significantly higher after jejunal administration in accordance with a low permeability compound. The effects of erythromycin suggest that absorption of fexofenadine involves an uptake transport in addition to passive diffusion in the jejunum and predominantly passive diffusion in the ileum and colon.

Transporter-mediated Intestinal Absorption of Fexofenadine in Rats

Both influx and efflux transporters are thought to be involved in the intestinal absorption of fexofenadine. The present study examined the influx transporter-mediated intestinal absorption of fexofenadine in rats, focusing on the role of rat oatp3 (Oatp1a5). The intestinal permeability of fexofenadine was evaluated by means of the Ussing chamber method in the presence of a P-glycoprotein inhibitor to block efflux transport. The permeability of fexofenadine from the mucosal to the serosal side was higher than that from the serosal side to the mucosal side. Transport of fexofenadine was saturable, and was significantly decreased by an organic anion transporting polypeptide (oatp) inhibitor. Furthermore, uptake of fexofenadine by Xenopus oocytes expressing rat oatp3 was significantly greater than that by water-injected oocytes, and the affinity of oatp3 for fexofenadine (Km) was about 60 microM, which is comparable with the value obtained by the Ussing chamber method using rat intestinal tissues. These results indicate that oatp3 plays a role as an influx transporter in the intestinal absorption of fexofenadine in rats.

Effect of Fruit Juices on the Oral Bioavailability of Fexofenadine in Rats

Fexofenadine has been identified as a substrate for both the efflux transporter, P-glycoprotein (P-gp), as well as the influx transporter, organic anion transporting polypeptide (OATP). Clinical studies in humans showed that fruit juices reduced the oral bioavailability of fexofenadine by preferentially inhibiting OATP over P-gp. The objective of this study was to investigate the effects of fruit juices on the oral absorption of fexofenadine in rats to establish a preclinical fruit juice–drug interaction model. In rats, fexofenadine was excreted unchanged in the urine, bile, and gastrointestinal tract, indicating minimal metabolism, making it an ideal probe to study transport processes. Coadministration of fexofenadine with ketoconazole, a P-gp inhibitor, increased the oral exposure of fexofenadine by 187%. In contrast, coadministration of fexofenadine with orange juice or apple juice to rats decreased the oral exposure of fexofenadine by 31 and 22%, respectively. Increasing the quantity of orange or apple juice administered further decreased the oral exposure of fexofenadine, by 40 and 28%, respectively. This reduction in fexofenadine bioavailability was moderate compared to that seen in humans. These findings suggest that in rats fruit juices may also preferentially inhibit OATP rather than P-gp–mediated transport in fexofenadine oral absorption, albeit to a lesser extent than observed in humans. This fruit juice–drug interaction rat model may be useful in prediction of potential food–drug interactions in humans for drug candidates.

The effect of ketoconazole on the in vivo intestinal permeability of fexofenadine using a regional perfusion technique.

To investigate whether the drug-drug interaction between fexofenadine and ketoconazole is localized to efflux transport proteins of the small intestine, and to determine and classify the effective jejunal permeability (Peff) of fexofenadine according to the Biopharmaceutics Classification System (BCS). Two separate jejunal perfusion experiments were performed using the Loc-I-Gut technique in eight healthy volunteers. During treatment 1 (T1), we investigated the acute effect of ketoconazole on the Peff and plasma pharmacokinetics of fexofenadine. In treatment 2 (T2) we examined the effect of oral pretreatment with ketoconazole (200 mg daily for 5 days) on the same absorption parameters. Each experiment was divided into two periods of 100 min and the jejunal segment was perfused with 93 micro m fexofenadine during both periods. In period 2 of each treatment, fexofenadine was coadministered with 94 micro m ketoconazole. The concentrations of fexofenadine in intestinal perfusate and plasma were measured by liquid chromatography with mass detection. During T1, the mean (+/- s.d.) Peff of fexofenadine was low according to the BCS (0.11 +/- 0.11 and 0.04 +/- 0.13 x 10(-4) cm s(-1) in periods 1 and 2, respectively), and the coadministration of ketoconazole in period 2 had no significant acute effect on Peff (95% confidence interval (CI) on the difference -0.37, 0.51). After pretreatment with ketoconazole (T2), the jejunal Peff of fexofenadine increased to 0.29 +/- 0.47 and 0.22 +/- 0.31 x 10-4 cm s(-1) in both periods 1 and 2, respectively, but the change was not statistically significant when compared with T1 (95% CI on the difference -0.62, 0.27 for T1 0-100 min vs T2 0-100 min; -0.54, 0.34 for T1 0-100 min vs T2 100-200 min). Fexofenadine plasma AUC from 0-100 mg showed no significant difference after pretreatment with ketoconazole (55 +/- 101 and 51 +/- 33 micro g ml(-1) min(-1) respectively; 95% CI on the difference -108, 115). Total plasma AUC (0-720 min) was 318 +/- 426 and 426 +/- 232 ng ml(-1) min in T1 and T2, respectively (95% CI on the difference -622, 405). No significant effect of acute coadministration or pretreatment with ketoconazole on the in vivo intestinal absorption of fexofenadine was detected in this study.