Effect of combination of pharmaceuticals on gastrointestinal absorption. I. Combination of caffeine with a few absorbable drugs

Drug complexes: Perspective from Academic Research and Pharmaceutical Market

Despite numerous research efforts, drug delivery through the oral route remains a major challenge to formulation scientists. The oral delivery of drugs poses a significant challenge because more than 40% of new chemical entities are practically insoluble in water. Low aqueous solubility is the main problem encountered during the formulation development of new actives and for generic development. A complexation approach has been widely investigated to address this issue, which subsequently improves the bioavailability of these drugs. This review discusses the various types of complexes such as metal complex (drug-metal ion), organic molecules (drug-caffeine or drug-hydrophilic polymer), inclusion complex (drug-cyclodextrin), and pharmacosomes (drug-phospholipids) that improves the aqueous solubility, dissolution, and permeability of the drug along with the numerous case studies reported in the literature. Besides improving solubility, drug-complexation provides versatile functions like improving stability, reducing the toxicity of drugs, increasing or decreasing the dissolution rate, and enhancing bioavailability and biodistribution. Apart, various methods to predict the stoichiometric ratio of reactants and the stability of the developed complex are discussed.

4 Final Report on the Safety Assessment of Sodium Dehydroacetate and Dehydroacetic Acid

Sodium Dehydroacetate and Dehydroacetic Acid are used as preservatives in cosmetic formulations at concentrations of 1.0 percent or less. Both compounds are rapidly absorbed when administered orally or on the skin of test animals.

Acute toxicity studies indicate that Sodium Dehydroacetate and Dehydroacetic Acid are slightly toxic when administered orally to rats. Neither compound was an irritant when applied to rabbit skin. Sodium Dehydroacetate was found to exhibit minimal eye irritation. Subchronic and chronic studies reveal various toxic effects, primarily due to the incurred lack of appetite and weight loss. No evidence of mutagenicity was reported for either ingredient use. No evidence of tumor induction by Dehydroacetic Acid was detected in a 64-week study. Dehydroacetic Acid had an inhibitory effect on hepatoma induction in rats when fed 4-(dimethylamino)azobenzene. A teratogenicity study in mice revealed no significant findings when compared to untreated controls.

Sodium Dehydroacetate, Dehydroacetic Acid, and cosmetics containing these ingredients were found practically nonirritating, nonsensitizing, nonphotosensitizing, and nonphototoxic in numerous clinical tests. On the basis of the available animal and clinical data, it is concluded that Sodium Dehydroacetate and Dehydroacetic Acid are safe as cosmetic ingredients in the present practices of use and concentration.

Thermodynamic parameters of molecular complexes in aqueous solution: enthalpy-entropy compensation in a series of complexes of caffeine with beta- naphthoxyacetic acid and drug-related aromatic compounds

Stability constants and thermodynamic parameters have been evaluated for the complexation reaction in aqueous solution of caffeine with beta-naphthoxy acetic acid. The values were higher than those previously reported for the complexation of other ligands with methyl xanthines. In nearly all aromatic ligands complexing with caffeine and theophylline for which data are available, both entropy and free energy of complexation were linearly related to the enthalpy, giving an isoequilibrium relationship. Salicylamide, sodium benzoate and cis-methyl cinnamate exhibited slight deviations on the delta G-delta H plot; the non-aromatic dehydroacetic acid showed the largest deviation. The isoequilibrium relationship was shown to be valid statistically (349-365 K, caffeine systems; 353-372 K, caffeine and theophylline systems) indicating underlying chemical causation. Thermodynamic equations are presented for analysis of the factor involved, which are attributed to a combination of substrate-ligand interactions and solvent effects. The substrate-ligand overlap area is considered as a common parameter through which the solvent and interaction forces might cooperate to give rise to linearity in the isoequilibrium relationship. The increasingly negative experimental values of the enthalpy and entropy with increase in ligand planar overlap area are discussed in relation to the underlying forces involved in the complexation.

Caffeine-phenacetin interaction in the rat: effects on absorption, metabolism and locomotor activity

The interactive effects of caffeine and phenacetin on the locomotor activity of the DA rat involved changes in absorption and metabolism as well as effects possibly exerted at the cns level. Phenacetin initially retarded the absorption of caffeine when coadministered by gavage but not when caffeine was given intraperitoneally and phenacetin orally. Phenacetin also increased the time for the plasma/caffeine concentration to peak, increased its peak concentration and prolonged its presence in the plasma. Urinary excretion patterns, suggested a blockade of the N-demethylation of caffeine by phenacetin. In contrast, caffeine had only a minor influence on the absorption and metabolism of phenacetin. The locomotor effects of the caffeine-phenacetin combination reflected the absorptive and metabolic interactions which occurred. Caffeine-induced hyperactivity was initially masked by phenacetin in a dose-dependent manner but after 2 h, when the plasma phenacetin concentrations were much lower, its retarding influence on caffeine metabolism became apparent and hyperactivity consequent upon an elevated plasma caffeine concentration was seen. Phenacetin also antagonized the hyperactive effects of theophylline and of (+)-amphetamine.