Influence of ionic strength on rectal absorption of gentamicin sulfate in the presence and absence of sodium salicylate

Feasibility Study for the Rectal Route of Administration for Gentamicin Evaluated in the Neonatal Minipig Model

Neonatal infections are a major cause of newborn mortality in low- and middle-income countries, particularly in areas without access to inpatient care. To address this, the World Health Organization developed guidelines for delivering simplified antibiotic regimens (oral amoxicillin and intramuscular gentamicin) in outpatient settings to young infants with suspected serious bacterial infection when referral is not feasible. However, there are still limitations to access, as the regimen requires a health care provider trained in giving intramuscular injections to infants. To provide a needle-free, simplified alternate to intramuscular delivery, PATH investigated the feasibility of the rectal administration of gentamicin. Potential formulations were screened by in vitro testing, and 2 liquid enema formulations and a cocoa butter suppository were developed and evaluated in a preclinical study of the rectal uptake of gentamicin in a neonatal minipig model. Sera samples from the control group, dosed by intramuscular injection, resulted in expected sera concentrations of gentamicin, but no gentamicin was detected in the sera of groups rectally dosed with the test formulations. The results of this study did not provide evidence to support the therapeutic feasibility of rectally absorbed gentamicin.

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 enhancement of rectally infused cefoxitin sodium by medium-chain fatty acids in conscious rats: concentration-effect relationship

The objective of this study was to assess the relative absorption promoting potency in terms of concentration-effect relationships of the medium-chain fatty acids hexanoic acid, octanoic acid, decanoic acid, and dodecanoic acid in conscious rats, using cefoxitin sodium as the rectally delivered model compound. Rectal uptake of cefoxitin, which was absorbed to a limited extent without enhancer (30 +/- 25%), proved to be significantly enhanced by 2.0 M sodium hexanoate, 0.69 M sodium octanoate, and 0.22 M sodium decanoate, resulting in mean bioavailabilities of 102 +/- 24, 68 +/- 25, and 68 +/- 10%, respectively. Thus, increasing fatty acid chain length results in increased enhancing potency from hexanoic acid to decanoic acid. However, using dodecanoate a statistically significant effect could not be reached, because of its limited aqueous solubility. Optimal chain length for absorption enhancement by medium-chain fatty acids is probably determined by interplay of intrinsic effects on mucosal permeability and solubility of the medium-chain fatty acid.

Rate-controlled absorption enhancement of rectally administered cefazolin in rats by a glyceride mixture (MGK)

The enhancing effect of the medium chain glyceride preparation MGK on the rectal absorption of the cephalosporin antibiotic cefazolin sodium was evaluated in relation to the rate of delivery. Cefazolin sodium proved to be absorbed to a small extent (15 to 27%) after rectal administration without MGK. Bolus administration with MGK enhanced rate and extent of cefazolin sodium absorption, resulting in a bioavailability of 57 +/- 26%. Linear infusion of 3 mg cefazolin sodium with MGK in 32 min produced complete absorption of the antibiotic (102 +/- 7%), but absorption occurred slower in comparison with bolus delivery. The rate of administration proved to be an important variable of the absorption enhancing effect of MGK.

Absorption of iothalamate after oral administration and absorption enhancement by amino acids in dogs and rats

The oral absorption of iothalamate and the effect of amino acids on its absorption were studied in 6 dogs and 6 rats using a simple HPLC assay. The results showed that iothalamate was absorbed in dogs, averaging 9.9, 8.5, and 10.0 per cent following the administration of 40 and 100 mg kg-1 of iothalamic acid capsules and 50 mg kg-1 of sodium iothalamate solution, respectively. The absorption from the capsule was slower and more sustained than that from the solution. In rats, the absorption appeared to be dose-independent (averaging about 4.2 per cent) in the dose range of 20-800 mg kg-1. The low bioavailability obtained was mainly due to the high polarity of iothalamate molecules as suggested by the GI recovery and in vitro partition studies. Among several amino acids tested as possible ion-pair formers, only homoarginine hydrochloride increased the partition of iothalamate into chloroform layer. However, both homoarginine hydrochloride and arginine hydrochloride at the amino acid/iothalamate molar ratio of 25 were found to significantly enhance (about 70 per cent) the iothalamate absorption in dogs. The in situ rat small intestinal loop study indicated that the absorption-enhancing effect of arginine was sodium dependent. At the sodium chloride concentration of 0.09 M, no significant increase in the absorption was observed, while at the concentration of 0.3 M or higher, a marked increase (about twofold) was obtained in both upper and lower intestine. Thus, the mechanism of the amino acids in facilitating the iothalamate absorption may be more closely related to the active amino acid transport system rather than the possible increase in lipophilicity of the ion-pair formed. The potential use of such naturally occurring, relatively non-toxic amino acids for increasing the GI absorption of water-soluble weak acids or bases through ion-pair formation remains to be fully investigated.

Use of adjuvants for enhancement of rectal absorption of cefoxitin in humans

The biological availability of cefoxitin administered rectally in the form of suppositories was examined in six human subjects by a cross-over design. Four different suppository systems containing adjuvants expected to enhance the absorption of the drug were studied. The presence of sodium salicylate and a nonionic surface-active agent, Brij 35, gave increased bioavailability as high as 20% compared with 3% for a system without adjuvants. The quantity of sodium salicylate was found to have an influence on the quantity of cefoxitin absorbed, and the salicylate was absorbed over an extended period of time from the rectum. The suppositories were well tolerated, and there were no adverse effects on bowel flora.