Interaction of some benzothiadiazine diuretics with beta-cyclodextrin

The interaction of three structurally related benzothiadiazine diuretics, viz., hydroflumethiazide, bendrofluazide and cyclopenthiazide wit beta-cyclodextrin was investigated. The study aimed at enhancing the solubility of these poorly soluble drugs via inclusion complexation with beta-cyclodextrin, Solubility measurements revealed that complexes were formed between each of three drugs and beta-cyclodextrin, The complexes were found to have 1:1 stoichiometric ratios and stability constants of 165.4, 55.7 and 27.9 M-1 for cyclopenthiazide, bendrofluazide and hydroflumethiazide, respectively. UV spectrophotometric analysis of the formed complexes agreed with the solubility results. The variation in the extent of binding between each of the three drugs and beta-cyclodextrin was attributed to their variation in molecular volume, partition coefficient and electrostatic properties of the binding sites.

Amorphous spray-dried hydroflumethiazide-polyvinylpyrrolidone systems: physiochemical properties

Hydroflumethiazide was spray-dried with polyvinylpyrrolidone (PVP) to produce products containing 0-30% PVP. These systems were amorphous and differed from previously prepared coprecipitates of similar composition. Differential scanning calorimetry (DSC) suggested that at low PVP weight fractions both amorphous drug and an amorphous drug-PVP complex can be present in spray-dried systems. The apparent solubility of hydroflumethiazide in spray-dried products increased with increasing PVP content reaching a plateau value approximately four times that of the pure crystalline drug. The estimated free energy and entropy of the spray-dried drug were greater than that of crystalline drug and also increased with increasing PVP content. Dissolution studies with compressed discs supported the apparent solubility data. The results suggest that amorphous phases having different orders of organization are formed in spray-dried systems with increasing PVP content.

The influence of polyvinylpyrrolidone on the dissolution properties of hydroflumethiazide

The incorporation of hydroflumethiazide with polyvinylpyrrolidone (PVP) was found to retard and to enhance the dissolution of the drug from compressed discs, the magnitude of the effect being dependent on the proportion of PVP present and its method of incorporation. The most active system dissolved sixteen times faster than pure hydroflumethiazide. Low concentrations of PVP were also found to decrease the apparent solubility of hydroflumethiazide while at high concentrations solubility was enhanced. X-ray and infrared analysis of systems suggested the presence of an amorphous form of hydroflumethiazide in coprecipitate systems. The dissolution data were consistent with a physical model which takes account of the roles played by crystalline and amorphous hydroflumethiazide together with the complexing and crystal growth inhibiting effect of PVP on hydroflumethiazide.

Permutation Trial of Diuretics

In order to increase the amount of information per day of observation the permutation trial is introduced in the study of acute effects of diuretic agents.

Chlorothiazide and hydroflumethiazide in optimal doses (2 Gm. and 200 mg. daily) and placebo tablets were given, 1 drug on each of the 3 days of the study, in all permutations to 12 patients treated by current methods for right heart failure.

The error variance of sodium, potassium, chloride, and water excretion was reduced by taking into account the variation due to permutations and days.

Chlorothiazide showed a stronger diuretic action than hydroflumethiazide, whereas the natriuretic effects were not significantly different as judged by analysis of variance. Hydroflumethiazide was less kaliuretic.

Magnesium excretion was independent of diuresis. Neither of the diuretics showed any effect on magnesium and calcium excretion. The ratio of sodium and chloride excretion was significantly lower during hydroflumethiazide than during chlorothiazide action.

The calculated sodium concentration in the additionally excreted urine during hydroflumethiazide administration was far above serum levels (the mean of 12 observations was 353 mEq. per liter), and significantly higher than during chlorothiazide action. This effect was also demonstrated in 6 control patients during water loading, suggesting that hydroflumethiazide increases free water reabsorption also when antidiuretic hormone is absent.

Comparison of the acute effects of diuretic agents is through the permutation trial made possible in the ordinarily equipped hospital without serious interference with current treatment.