Rate-controlled rectal absorption enhancement of cefoxitin by co-administration of sodium salicylate or sodium octanoate in healthy volunteers

Safety of surfactant excipients in oral drug formulations

Surfactants are a diverse group of compounds that share the capacity to adsorb at the boundary between distinct phases of matter. They are used as pharmaceutical excipients, food additives, emulsifiers in cosmetics, and as household/industrial detergents. This review outlines the interaction of surfactant-type excipients present in oral pharmaceutical dosage forms with the intestinal epithelium of the gastrointestinal (GI) tract. Many surfactants permitted for human consumption in oral products reduce intestinal epithelial cell viability in vitro and alter barrier integrity in epithelial cell monolayers, isolated GI tissue mucosae, and in animal models. This suggests a degree of mis-match for predicting safety issues in humans from such models. Recent controversial preclinical research also infers that some widely used emulsifiers used in oral products may be linked to ulcerative colitis, some metabolic disorders, and cancers. We review a wide range of surfactant excipients in oral dosage forms regarding their interactions with the GI tract. Safety data is reviewed across in vitro, ex vivo, pre-clinical animal, and human studies. The factors that may mitigate against some of the potentially abrasive effects of surfactants on GI epithelia observed in pre-clinical studies are summarised. We conclude with a perspective on the overall safety of surfactants in oral pharmaceutical dosage forms, which has relevance for delivery system development.

Formulation strategies to improve the efficacy of intestinal permeation enhancers. Adv Drug Deliv Rev 2021;177:113925. [PMID: 34418495 DOI: 10.1016/j.addr.2021.113925]

The use of chemical permeation enhancers (PEs) is the most widely tested approach to improve oral absorption of low permeability active agents, as represented by peptides. Several hundred PEs increase intestinal permeability in preclinical bioassays, yet few have progressed to clinical testing and, of those, only incremental increases in oral bioavailability (BA) have been observed. Still, average BA values of ~1% were sufficient for two recent FDA approvals of semaglutide and octreotide oral formulations. PEs are typically screened in static in vitro and ex-vivo models where co-presentation of active agent and PE in high concentrations allows the PE to alter barrier integrity with sufficient contact time to promote flux across the intestinal epithelium. The capacity to maintain high concentrations of co-presented agents at the epithelium is not reached by standard oral dosage forms in the upper GI tract in vivo due to dilution, interference from luminal components, fast intestinal transit, and possible absorption of the PE per se. The PE-based formulations that have been assessed in clinical trials in either immediate-release or enteric-coated solid dosage forms produce low and variable oral BA due to these uncontrollable physiological factors. For PEs to appreciably increase intestinal permeability from oral dosage forms in vivo, strategies must facilitate co-presentation of PE and active agent at the epithelium for a sustained period at the required concentrations. Focusing on peptides as examples of a macromolecule class, we review physiological impediments to optimal luminal presentation, discuss the efficacy of current PE-based oral dosage forms, and suggest strategies that might be used to improve them.

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.

Do surface-active lipids in food increase the intestinal permeability to toxic substances and allergenic agents?

The incidence of many common diseases has increased during the last decades. High fat intake is a risk factor for many diseases. We propose that some of the negative effects of fat are caused by lipid-induced damage of the gastrointestinal epithelium, thus compromising the epithelial function as a barrier for passage of toxic substances and allergenic agents to the circulatory system. Monoglycerides (MGs), phospholipids and fatty acids (FAs) are surface-active molecules that in pharmaceutical studies act as permeability enhancers for hydrophilic drugs with low absorption. Three possible mechanisms were proposed: (a) lipid-induced alterations in intracellular events may cause destabilization of tight junctions between the GI epithelial cells, (b) lipids may destabilize cell membranes, (c) lipids cause intestinal cell damage, which increase the permeability of the GI epithelium. These "side effects" of lipids may partly explain the association between fat intake and disease observed in epidemiological studies.

The influence of caprate on rectal absorption of phenoxymethylpenicillin: experience from an in-vivo perfusion in humans

The aim of this in-vivo perfusion study in humans was to investigate the influence of a penetration enhancer, sodium caprate, on the rectal absorption of phenoxymethylpenicillin and antipyrine. Six subjects, 3 male and 3 female, were included in two separate studies using perfusion solution of different pH (T1 and T2, respectively). Each in-vivo rectal perfusion investigation lasted for 200 min and consisted of two periods of 100 min, the first serving as a control, and sodium caprate being added in the second period in both T1 and T2. The concentrations of phenoxymethylpenicillin, antipyrine and sodium caprate in the outlet perfusate were assayed by HPLC, as was the plasma concentrations of phenoxymethylpenicillin. At pH 6.0 (0-100 min) the fraction absorbed (f(abs)) and effective permeability (P(eff)) of phenoxymethylpenicillin were 0.3% and 0.06 x 4 cm s(-1), respectively, and remained unaffected by the addition of sodium caprate. When the same subjects were perfused at pH 7.4, the f(abs) and P(eff) of phenoxymethylpenicillin were 2.4% and 0.11 x 10(-4) cm s(-1) (0-100 min), respectively, also remaining unchanged by addition of sodium caprate (100-200 min). It was possible to determine the plasma AUC of phenoxymethylpenicillin after addition of sodium caprate in three subjects at both pHs; this was in the range of 14.0-62.8 and 56.4-231 (min micromol L(-1)) at pH 6.0 and 7.4, respectively. Interestingly, there was a correlation between P(eff) for sodium caprate and the individual plasma AUC and C(max) of phenoxymethyl-penicillin, which indicates that the permeability of the enhancer in the tissue upon which it should act is crucial for achieving an effect. The f(abs) and the P(eff) of antipyrine were not affected at either pH when sodium caprate was added to the perfusion solution. In conclusion, the plasma pharmacokinetics of phenoxymethylpenicillin suggested a slightly increased rectal absorption at pH 7.4 in subjects where sodium caprate was transported into the rectal tissue. However, the increased P(eff) for phenoxymethylpenicillin wastoo small to detectfrom the outlet perfusate, which suggests that sodium caprate alone has a limited effect on the permeability in-vivo across the rectal epithelium when it is presented in a solution.

Relative hypoglycemic effect of insulin suppositories in diabetic beagle dogs: optimization of various concentrations of sodium salicylate and polyoxyethylene-9-lauryl ether

The effect of insulin suppositories containing different amounts and concentrations of sodium salicylate (50, 100 mg) and polyoxyethylene-9-lauryl ether (POELE 1, 3, 4%), respectively, on the plasma glucose concentration of diabetic beagle dogs was investigated after rectal administration. Comparison of the effects of these formulations was made with that produced after subcutaneous insulin injections. Insulin suppositories containing sodium salicylate (50 mg) produced a maximum reduction of plasma glucose concentration (Cmax) of 55 +/- 11%, an area under the curve (AUC) of 252 +/- 59% reduction h; and a relative hypoglycemia (RH) of 49 +/- 12% relative to subcutaneous injection of insulin (4 U/kg). Increasing sodium salicylate to 100 mg/suppository did not improve the hypoglycemic effect of insulin suppositories further. Investigation of the influence of insulin suppositories containing different concentrations of the nonionic surfactant POELE (1, 3, 4%) showed that; the suppositories containing the lowest concentration (1%) produced the highest hypoglycemic effect with a Cmax of 68%, AUC of 332 +/- 67% reduction h, and RH of 55 +/- 11%. Incorporation of sodium salicylate 50mg in insulin suppositories containing 1% POELE did not improve further the effects found with these suppositories. In conclusion, a relative hypoglycemic effect of about 50-55% can be achieved using insulin suppositories containing Witepsol W35 as a base, insulin (5 U/kg), and sodium salicylate (50 mg) or POELE (1%) as rectal absorption enhancers.

Effects of absorption enhancers in chloroquine suppository formulations: I. In vitro release characteristics

The need to develop chloroquine suppository formulations that yield optimal bioavailability of the drug has been emphasized. This study demonstrates the effects of incorporation of known absorption-enhancing agents (nonionic surfactants and sodium salicylate) on the in vitro release characteristics of chloroquine from polyethylene glycol (1000:4000, 75:25%, w/w) suppositories. The release rates were determined using a modification of the continuous flow bead-bed dissolution apparatus for suppositories. Results showed that the extent of drug release from suppositories containing any of three surfactants (Tween 20, Tween 80 and Brij 35) was 100%, whereas 88% release was obtained with control formulation (without enhancer) (P<0.05). However, Tween 20 was more effective than Brij 35 and Tween 80 in improving the drug release rate. There was a concentration-dependent effect with Tween 20, and 4% (w/w) of this surfactant was associated with the highest increase in the rate of drug release from the suppositories. Sodium salicylate at a concentration of 25% (w/w) also significantly enhanced the drug release rate, but a higher concentration of the adjuvant markedly reduced both the rate and extent of drug release. Combined incorporation of Tween 20 and sodium salicylate did not significantly modify (P0.05) the rate of drug release when compared to the effect of the more effective single agent. Due to their effects in improving the drug release profiles coupled with their intrinsic absorption-promoting properties, it is suggested that incorporation of 4% (w/w) Tween 20 and/or 25% (w/w) sodium salicylate in the composite polyethylene glycol chloroquine suppository formulations, may result in enhancement of rectal absorption of the drug. This necessitates an in vivo validation.

Alternative routes of drug administration--advantages and disadvantages (subject review). American Academy of Pediatrics. Committee on Drugs

During the past 20 years, advances in drug formulations and innovative routes of administration have been made. Our understanding of drug transport across tissues has increased. These changes have often resulted in improved patient adherence to the therapeutic regimen and pharmacologic response. The administration of drugs by transdermal or transmucosal routes offers the advantage of being relatively painless.12 Also, the potential for greater flexibility in a variety of clinical situations exists, often precluding the need to establish intravenous access, which is a particular benefit for children.

This statement focuses on the advantages and disadvantages of alternative routes of drug administration. Issues of particular importance in the care of pediatric patients, especially factors that could lead to drug-related toxicity or adverse responses, are emphasized.

Pharmacokinetics of rectal drug administration, Part II. Clinical applications of peripherally acting drugs, and conclusions

Part I of this article, which appeared in the previous issue of the Journal, covered general considerations, the physiology of the rectum, spreading of drugs into the colon, rectal absorption, partial avoidance of first-pass elimination, rate-controlled rectal delivery of drugs, irritation of the rectal mucosa and clinical applications of rectal administration, and discussed centrally acting drugs. In Part II, this discussion is extended to drugs which act peripherally and to methods of enhancing rectal drug absorption. The overall summary appeared in Part I.