Exploitation of the intestinal oligopeptide transporter to enhance drug absorption

Influence of enhancers on the absorption and on the pharmacokinetics of cefodizime using in-vitro and in-vivo models

In the development of novel antibiotics, more and more compounds have been found that cannot be absorbed orally and, therefore, must be administered intravenously or intramuscularly. Because of the obvious drawbacks of drug delivery by injection, the development of alternatives with enhanced oral bioavailability has received much attention in pharmaceutical research. Cefodizime, a novel third-generation cephalosporin with significant advantages in the parenteral treatment of common infections, was used as a model drug. Cefodizime behaves as a highly hydrophilic compound, as shown from its extremely low partition coefficient. The effect of cationic absorption enhancers (hexadecyldimethyl-benzylammonium chloride, N-hexadecylpyridinium bromide, dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide) on the lipophilicity of cefodizime was investigated by means of the n-octanol/water system. Results showed that the counter-ions had a positive influence on the solubility of cefodizime. These results on partitioning coefficients in the n-octanol/buffer system were confirmed using an in-vitro transport model with artificial and biological membranes (Caco-2-cells). Furthermore, the physiological compatibility of the absorption enhancers was investigated using the active d-glucose transport. The pharmacokinetic profile of cefodizime was evaluated in rabbits after intraduodenal administration with and without an absorption enhancer.

Reducing dosing frequency of carbidopa/levodopa: double-blind crossover study comparing twice-daily bilayer formulation of carbidopa/levodopa (IPX054) versus 4 daily doses of standard carbidopa/levodopa in stable Parkinson disease patients

OBJECTIVE

We compared IPX054, a bilayer tablet of immediate- and extended-release carbidopa/levodopa (CD/LD) given twice daily to standard CD/LD given 4 times daily in patients with stable Parkinson disease (PD).

METHODS

Twelve PD patients with no or mild fluctuations on CD/LD 25/100 mg 4 times daily were randomized to a double-blind crossover comparison with IPX054 (50/200 mg) twice daily. At the end of each 2-week treatment, patients were video recorded while performing a modified Unified Parkinson's Disease Rating Scale motor examination and Rush Dyskinesia Rating Scale at 30-minute intervals over 8.5 hours. The primary outcome measure was the number of videotape epochs rated as "ON" without troublesome dyskinesia by a blinded observer (Wilcoxon signed rank tests).

RESULTS

The 9 men and 3 women had a mean age of 69 years and mean PD duration of 6 years. IPX054 and CD/LD showed no significant differences in the primary outcome measure (mean number of video epochs rated as ON without troublesome dyskinesia; P = 0.14). The mean time to ON was improved with IPX054 (P = 0.014), and the mean modified Unified Parkinson's Disease Rating Scale scores slightly favored IPX054 (14.4 vs 16.9; P = 0.052). Mean Rush Dyskinesia Rating Scale scores were not significantly different between IPX054 and CD/LD (0.45 vs 0.69; P = 0.25). No patient developed troublesome dyskinesias.

CONCLUSIONS

In stable PD patients, no difference was detected between twice-daily treatment with IPX054 and CD/LD given 4 times daily. In this group, substitution with IPX054 reduced dosing frequency while maintaining CD/LD efficacy. In clinical practice, this ease of administration may offer improved treatment compliance.

In-vitro and in-vivo studies of cefpirom using bile salts as absorption enhancers

Cephalosporins have to be administered by injection because of the poor intestinal absorption of the orally delivered drugs. Because of the obvious drawbacks of drug delivery by injection, the development of alternatives with enhanced oral bioavailability is receiving much attention in pharmaceutical research. Cefpirom (Cp) is a new semi-synthetic amino-2-thiazolyl-methoxyimino cephalosporin that has been substituted in position 3 with a cyclopenteno-pyridinium group in order to create a zwitterionic compound. It exhibits highly hydrophilic properties, as shown from its extremely low partition coefficient, and therefore its lipophilicity was increased using bile salts. The effect of this on the partition coefficients determined in the n-octanol/buffer system was confirmed using an in-vitro transport model with artificial and biological membranes. The pharmacokinetic properties of Cp were investigated in rabbits after intraduodenal administration with and without bile salts. Furthermore, the physiological compatibility of the bile salts was investigated using active D-glucose transport.