Effect of phenothiazines, disodium ethylenediaminetetraacetic acid and diethyl maleate on in vitro rat colonic transport of cefmetazole and inulin

Intestinal permeation enhancers for oral peptide delivery

Intestinal permeation enhancers (PEs) are one of the most widely tested strategies to improve oral delivery of therapeutic peptides. This article assesses the intestinal permeation enhancement action of over 250 PEs that have been tested in intestinal delivery models. In depth analysis of pre-clinical data is presented for PEs as components of proprietary delivery systems that have progressed to clinical trials. Given the importance of co-presentation of sufficiently high concentrations of PE and peptide at the small intestinal epithelium, there is an emphasis on studies where PEs have been formulated with poorly permeable molecules in solid dosage forms and lipoidal dispersions.

Absorption enhancers in pulmonary protein delivery

Extensive research efforts have been directed towards the systemic administration of therapeutic proteins and poorly absorbed macromolecules via various nontraditional, injection-free administration sites such as the lung. As a portal for noninvasive delivery, pulmonary administration possesses several attractive features including a large surface area for drug absorption. Nevertheless, achieving substantial bioavailability of proteins and macromolecules by this route has remained a challenge, chiefly due to poor absorption across the epithelium. The lungs are relatively impermeable to most drugs when formulated without an absorption enhancer/promoter. In an attempt to circumvent this problem, many novel absorption promoters have been tested for enhancing the systemic availability of drugs from the lungs. Various protease inhibitors, surfactants, lipids, polymers and agents from other classes have been tested for their efficacy in improving the systemic availability of protein and macromolecular drugs after pulmonary administration. The purpose of this article is to provide the reader with a summary of recent advances made in the field of pulmonary protein delivery utilizing absorption enhancers. This report reviews the various agents used to increase the bioavailability of these drugs from the lungs, their mechanisms of action and effectiveness, and their potential for toxicity.

In vitro permeation study of a mucoadhesive drug delivery system for controlled delivery of nonoxynol-9

A carbopol 934P-based drug delivery system (AmDDS) was developed to achieve the dual-controlled delivery of Nonoxynol-9 (N-9), a spermicidal agent, and EDTA, a potentiator of spermicidal activity. This gel-type system made intimate contact with vaginal mucosa and maintained an effective drug concentration within the vagina for a prolonged period of time. An existing mathematical model, based on a unilayer diffusion membrane, was applied for describing permeation of N-9 through vaginal mucosa. Vaginal permeation of N-9 from AmDDS was negligible over the initial 5 hr, then increased in a Q versus t pattern, but remained low. A relationship was observed between the permeation rate (Js) of drug through vaginal mucosa and the release flux (Q/t1/2) from AmDDS, which showed that the permeation rate (Js) increased with increased square of the release flux [(Q/t1/2)2] in a hyperbolic manner. This result indicated that release of N-9 from AmDDS is still the rate-limiting step at doses within the tested range. EDTA, at concentration of up to 0.32%, did not change the permeation rate of N-9 through vaginal mucosa. It is thus concluded that the developed AmDDS can control the intravaginal delivery of N-9 as well as its permeation through vaginal mucosa.

Efficacy of cefmetazole in the treatment of active syphilis in the rabbit model

Cefmetazole, a cephamycin-type antibiotic, was shown to be as effective as standard benzathine penicillin for therapy of active syphilis in the rabbit model. Four groups of six adult male rabbits were inoculated intradermally with 10(6) Treponema pallidum per site, producing primary syphilitic lesions. One week following infection, groups of rabbits were treated with benzathine penicillin (200,000 U intramuscularly weekly for 2 weeks) or cefmetazole (20 or 40 mg/kg per day intramuscularly in four divided doses for 15 days); one group was untreated. Daily dark-field microscopic examination of lesion aspirates demonstrated that the mean times to dark-field negativity were the same for benzathine penicillin- and two cefmetazole-treated groups (1.0. 1.0, and 1.17 days, respectively), while all untreated animals remained dark-field positive for greater than 15 days. Mean maximum lesion diameters in cefmetazole-treated animals (8.7 +/- 1.3 and 8.1 +/- 1.3 mm) were equivalent to those in penicillin-treated animals (8.6 +/- 1.6 mm) and were smaller than observed in untreated animals (12.4 +/- 2.2 mm; P less than 0.01); fewer lesions ulcerated in penicillin- or cefmetazole-treated rabbits than in untreated rabbits (P less than 0.001). Persistent infection was documented in lymph nodes of untreated rabbits; no evidence of latent infection was found in penicillin- or cefmetazole-treated animals.

3-Amino-1-hydroxypropylidene-1,1-diphosphonate (APD): a novel enhancer of rectal cefoxitin absorption in rats

The promoting action of the calcium chelating compound EDTA on intestinal drug absorption is supposed to be based on Ca2+ depletion, inducing widening of tight junctions. The aim of the present study was to evaluate the effects of the calcium-binding agent 3-amino-1-hydroxypropylidene-1,1-diphosphonate disodium salt (APD) on rectal cefoxitin absorption in rats. The extent of rectal cefoxitin absorption was enhanced by 0.5 to 6% w/v of APD, on rectal infusion as well as on bolus delivery, the latter regimen tending to result in lower bioavailabilities. A maximal cefoxitin bioavailability of 85 +/- 10% was achieved by infusion with 4% w/v of APD, compared with 14 +/- 12% without APD.

Site dependence of absorption-promoting actions of laureth-9, Na salicylate, Na2EDTA, and aprotinin on rectal, nasal, and buccal insulin delivery

The site dependence of the absorption-promoting actions of laureth-9, Na salicylate, Na2EDTA, and aprotinin was studied in rats. Insulin absorption was estimated on the basis of the cumulative hypoglycemic response from 0 to 4 hr postdose, relative to that after intramuscular insulin. Insulin was administered with or without adjuvants to isolated rectal, nasal, and buccal absorption sites. Laureth-9, a nonionic surfactant which irreversibly removes membrane proteins or lipids, promoted insulin absorption from each site. The rectal, nasal, and buccal routes were 30% as effective as the i.m. route. The enhancing effects of Na salicylate and Na2EDTA, which have reversible mechanisms of permeability enhancement, were specific for rectal absorption. With these adjuvants, rectal insulin was 30-40% as effective as i.m. insulin, but nasal and buccal doses were less than 5% as effective as i.m. doses. This specificity can be at least partly explained by considering the site-to-site differences in membrane histology, although differences in pore size and membrane biochemistry might also contribute. The protease inhibitor aprotinin was ineffective in increasing insulin efficacy via each route, either alone or in combination with laureth-9.