Oral drug administration, surfactants

In the past two decades, many studies have tested adjuvants that act by either permeabilizing the rectal mucosa or inhibiting drug degradation. Oral and rectal routes of drug administration are unsuitable for adequate absorption of various compounds with a peptide or protein structure and of several hydrophilic antibiotics. The use of absorption enhancers, e.g., salicylates, enamines, surfactants, and straight-chain fatty acids, has gained wide interest... 

Parenteral (injected) administration of drugs provides a solution to many problems associated with the oral delivery route. A drug injected into the blood circulation is considered to be completely bioavail-able thaefore, the quantity of the surfactants and otha inactive excipients in intravenous dosage forms are usually strictly limited. The most common alternative routes of parenteral drug administration are intramuscular or subcutaneous injections [2], Several otha injection routes are available to elicit rapid local reaction, such as intrathecal, intraarticular, and intracardiac. 

Penetration enhancers are low molecular weight compounds that can increase the absorption of poorly absorbed hydrophilic drugs such as peptides and proteins from the nasal, buccal, oral, rectal, and vaginal routes of administration [186], Chelators, bile salts, surfactants, and fatty acids are some examples of penetration enhancers that have been widely tested [186], The precise mechanisms by which these enhancers increase drug penetration are largely unknown. Bile salts, for instance, have been shown to increase the transport of lipophilic cholesterol [187] as well as the pore size of the epithelium [188], indicating enhancement in both transcellular and paracellular transport. Bile salts are known to break down mucus [189], form micelles [190], extract membrane proteins [191], and chelate ions [192], While breakdown of mucus, formation of micelles, and lipid extraction may have contributed predominantly to the bile salt-induced enhancement of transcellular transport, chelation of ions possibly accounts for their effect on the paracellular pathway. In addition to their lack of specificity in enhancing mem-... 

Surfactants are employed in nanoparticle suspensions. Chen et al. (2002) evaluated the pre paration of amorphous nanoparticle suspensions containing cyclosporine A using the evaporative precipitation into aqueous solution (ERAS) system. The effect of particle size was studied varying the drug surfactant ratios, type of surfactants, temperature, drug load, and solvent. Acceptable particle sizes suitable for both oral and parenteral administration were also studied. Additional articles in the nanoparticle delivery of poorly water-soluble drugs include Kipp (2004), Perkins et al. (2000), Young et al. (2000), and Tyner et al. (2004). 

Microemulsions are thermodynamically stable, isotropically clear dispersions composed of a polar solvent, oil, a surfactant, and a cosurfactant. Microemulsions have much potential for drug delivery as very hydro-phobic molecules can be solubilized and formulated for oral administration. All of the commercial products are actually non-aqueous microemulsions, also known as microemulsion preconcentrates or SEDDS, as the polar solvent is not water. Upon contact with aqueous media such as gastrointestinal fluids, a SEDDS formulation spontaneously forms a fine dispersion or aqueous microemulsion. 

Bioavailability of triamterene has been studied in healthy human subjects.59 62 65 79 The bioavailability of triamterene was found to be 52%, corresponding to absorption of 83%, in a study done in six volunteers after intravenous administration of the drug.62 Another study reported that triamterene bioavailability from capsules was poorer and more variable than that from suspension.65 Effect of various vehicles and vehicle volumes on oral bioavailability of triamterene has been investigated.80 Addition of a combination of a surfactant and carbonate or bicarbonate as diluents to a triamterene gelatin capsule is reported to result in better bioavailability of the drug.81 When both calcium carbonate and cetylpyridinium chloride were present in a triamterene capsule the dissolution rates were greatly increased over triamterene capsules containing neither diluent or either... 

The use of pharmaceuticals in form of emulsions is of special interest. Thus, for example, o/w emulsions stabilised by surfactants, such as mono- and diglycerides, are successfully used as pseuo-doxime-proxetil protection from intestinal lumen hydrolysis through oral administration [128]. Multiple w/o/w emulsions stabilised by Tween 20/Span 20 or Tween 80/Span 80 mixtures contributed to a prolonged retention of cytarabine in one of the phases, and its gradual release ensured a prolonged action of the drug [129]. 

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