In order to obtain experimental evidence for the complexation between β-cyclodextrin and piroxicam (4-hydroxy-2-methyl-N-2-pyridyl-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide) and to investigate the thermodynamics of this interaction, a flow microcalorimetric study of this system has been undertaken. In fact, the mixing of ,β-cyclodextrin and piroxicam in ratio 1:1 in given experimental conditions gives rise to a system showing better pharmacological properties than piroxicam alone. The results confirm the formation of a complex between β-cyclodextrin and piroxicam and allow the evaluation of the equilibrium constant for the process, assuming the formation of a 1: 1 complex. It results in log K′ = 3.54, where K′ is the apparent formation constant at pH 9.00, in good agreement with literature data for similar compounds. The values of ΔH and ΔS are also reported.

Abstractγ‐Cyclodextrin was used to perform chiral discrimination of (±)‐5,6‐diisobutyroyl‐2‐methylaminotetralin hydrochloride by 1H‐NMR; the 95% enantiomeric excess of the (–)‐isomer was determined successfully. © 1992 Wiley‐Liss, Inc.

To improve the biopharmaceutical performance of the nonsteroidal anti-inflammatory drug piroxicam, inclusion compounds with β-cyclodextrin carrier have been prepared and studied for a wide range of chemical, physical and pharmaceutical properties.

A method based on DSC measurements which allows the determination of the stoichiometry of a drug-cyclodextrin complex has been developed. A practical example on the vinburnine-gammacyclodextrin complex isolated by the authors is presented and discussed.

In a comparative study on rodents and on man the fundamental pharmacokinetic properties of 4-hydroxy-2-methyl-N-(2-pyridyl)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide (piroxicam) were assessed and the bioavailability of the drug after oral and rectal administration was determined. It was found that: the plasma half-life is much longer in man (ca. 35 h) than in rodents (3--5.5 h in the rabbit, 5 h in the rat and mouse). The long plasma disappearance time in man is attributed to the relatively strong binding with the plasma proteins. A thorough pharmacokinetic analysis in the rabbit revealed a two-compartment distribution of the drug with an intercompartmental t 1/2 0.67 h and an excretion + metabolisation t 1/2 of 3.16 h. The extremely low excretion of the drug as such or as the glucuronide in the bile and urine suggests that the main excretion route is metabolic. The rectal bioavailability is similar to the oral bioavailability both in rabbit and rat and in man. Comparison of the AUC after i.v. injection with the AUCs after oral and rectal administration in the rabbit seems to show that absorption by rectal and oral route is quantitative.