NSAID Gastropathy

From Solution Studies of Pharmaceuticals (Aspirin and Related Compounds) to the Thermodynamics of Aspirin-β-Cyclodextrin Interaction in water and N,N-Dimethylformamide

The solution behavior of pharmaceuticals (acetylsalicylic acid, 4-acetoxybenzoic acid and 5-acetylsalicylic acid) in water and N,N-Dimethylformamide (DMF) at 298.15 K were investigated through solubility, conductance and calorimetric measurements. Taking into account the formation of ion pairs of these pharmaceuticals in water, the solution Gibbs energies of the dissociated electrolytes in this solvent were calculated. Thus, the solution thermodynamics of these compounds in water are reported using enthalpy data obtained by calorimetry. These pharmaceuticals undergo solvation when exposed to a saturated atmosphere of DMF. As the composition of the solid is not the same as that in solution, the Gibbs energy of the solutions of these compounds could not be obtained; only enthalpy data are reported. The thermodynamics of the interaction of acetylsalicylic acid (aspirin) with β-cyclodextrin in water and DMF is fully discussed, emphasizing the two different processes that take place in water at the two different pHs. In all cases, the favorable Gibbs energies for these processes are entropically controlled, mainly resulting from the higher dehydration/desolvation that the receptor undergoes upon interaction with the guest.

Nonsteroidal antiinflammatory drug-related injury to the gastrointestinal tract: clinical picture, pathogenesis, and prevention

Increasing life expectancy in developed countries has led to a growing prevalence of arthritic disorders, which has been accompanied by increasing prescriptions for nonsteroidal antiinflammatory drugs (NSAIDs). These are the most widely used agents for musculoskeletal and arthritic conditions. Although NSAIDs are effective, their use is associated with a broad spectrum of adverse reactions in the liver, kidney, cardiovascular system, skin, and gut. Gastrointestinal (GI) side effects are the most common. The dilemma for the physician prescribing NSAIDs is, therefore, to maintain the antiinflammatory and analgesic benefits, while reducing or preventing GI side effects. The challenge is to develop safer NSAIDs by shifting from a focus on GI toxicity to the increasingly more appreciated cardiovascular toxicity.

Anti-inflammatory, analgesic and ulcerogenic properties of S-(+)-ibuproxam, racemic ibuproxam-beta-cyclodextrin and S-(+)-ibuproxam-beta-cyclodextrin

The anti-inflammatory, analgesic and gastric mucosal damage-inducing activities of S-(+)-ibuproxam, and S-(+)-ibuproxam-beta-cyclodextrin, new propionic acid derivatives, and racemic ibuproxam-beta-cyclodextrin were investigated in three animal models and compared with those of racemic ibuproxam, racemic ibuprofen and its optical enantiomer S-(+)-ibuprofen. The anti-inflammatory activities of racemic ibuprofen, S-(+)-ibuprofen and racemic ibuproxam in carrageenan-induced paw oedema in rats were almost equipotent and slightly greater than those of S-(+)-ibuproxam and S-(+)-ibuproxam-beta-cyclodextrin, and significantly greater than that of racemic ibuproxam-beta-cyclodextrin. In abdominal constriction tests in mice, the analgesic effects of racemic ibuproxam, S-(+)-ibuproxam, racemic ibuproxam-beta-cyclodextrin and S-(+)-ibuproxam-beta-cyclodextrin were significantly less pronounced than those of racemic ibuprofen and S-(+)-ibuprofen. Ulcerogenic activity of S-(+)-ibuproxam-beta-cyclodextrin in rats was found to be significantly weaker than that of racemic ibuproxam-beta-cyclodextrin, racemic ibuproxam and S-(+)-ibuproxam and, most notably, weaker than those of racemic ibuprofen and S-(+)ibuprofen. These results indicate that S-(+)-ibuproxam-beta-cyclodextrin could be a novel potent anti-inflammatory and analgesic agent with a therapeutic index more favourable than that of the classical non-steroid anti-inflammatory drugs ibuprofen and ibuproxam.

Inclusion complexation of heptakis(2,6-di-O-ethyl)-beta-cyclodextrin with tiaprofenic acid: pharmacokinetic consequences of a pH-dependent release and stereoselective dissolution

beta-Cyclodextrin was ethylated at the 2- and 6-hydroxyl positions. Diethyl sulfate was employed as an alkylating reagent. NMR spectra data indicate that heptakis(2,6-di-O-ethyl)-beta-cyclodextrin (DCD) is the principal component of the product obtained. In addition, the FAB mass spectra obtained in nitrobenzyl alcohol and glycerin matrices gave pseudo-molecular ions with m/z ratios of 1630.75 and 1711.90 corresponding to C70H126O35[2Na.NaCl] and C70H126O35[2C3H8O3], respectively. The dissolution of tiaprofenic acid (TA) enantiomers, from TA powder (10 mg) and inclusion complex and/or coprecipitate (IC) (TA:DCD 1:1 molar ratio, equivalent to 10 mg of free TA), were examined using the dispersion method at pH values of 1.5, 3.0, and 7.4. Complex formation with the hydrophobic DCD resulted in a significant reduction in the release rate of both R- and S-TA, as compared to that observed with the powder. At pH 1.5, tiaprofenic acid enantiomers were not released from IC, compared to 20.52 +/- 1.47% of R-TA and 20.47 +/- 1.64% of S-TA dissolved from the powder. The greatest stereoselectivity in release profiles was found at pH 3.0 from IC [S:R 24 h cumulative percent release (sigma R24) ratio of 0.88 +/- 0.04]. Elevation of the pH to 7.4, which resulted in a faster dissolution and greater sigma R24 of enantiomers from both powder and IC, was accompanied by a parallel reduction in the stereoselectivity. Following single 20 mg/kg oral doses of racemic TA as both powder or IC to Sprague-Dawley rats, significant stereoselectivity was observed in the plasma concentration profiles of the enantiomers (S:R AUC(0-infinity) = 1.5). Despite significant reduction in the rate and extent of absorption, there was not a significant difference in the observed in vivo stereoselectivity between the two formulations. Therefore the in vivo importance of the observed stereoselectivity in release at pH 3.0 is ruled out. Nevertheless, consideration must be given to the possibility of stereoselective release when chiral excipients are used in the formulation of racemic drugs.