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Biomedical subjects

P A Laskar

Publications and source records attributed to P A Laskar.

7 recordsLinked to original sources
PubMed1977

Degradation of carmustine in aqueous media.

The degradation rate of carmustine was investigated in buffered aqueous media at several pH values. The buffering agents studied were those with potential use in parenteral formulations of this drug: acetate, citrate, and phosphate. The apparent first-order degradation rate constants were calculated using a linear regression procedure. A pH range over which minimum degradation occurred was ascertained. General acid and specific base catalysis was demonstrated for the degradation of carmustine. From the data at 5, 22, and 37 degrees, the apparent activation energies for carmustine degradation in buffered aqueous media were computed and were strongly pH dependent.

Buffers↗
PubMed1977

Degradation of carmustine in mixed solvent and nonaqueous media.

The degradation rate of carmustine in several solvent mixtures and in mannitol solution was investigated at 5, 22, and 37 degrees. The solvents chosen were those utilized as parenteral diluents. The apparent first-order degradation rate constants were computed using a linear regression procedure. The most nonaqueous solvent mixtures demonstrated minimum apparent degradation rates. The apparent degradation rate constant decreased with a decrease in the macroscopic dielectric constant. From the data at several temperatures, the apparent activation energies for carmustine degradation in the several solvent mixtures were calculated. There was no evidence for a relationship between the apparent activation energy and the dielectric constant.

Carmustine↗
PubMed1976

Absorption and distribution of radioactivity from suppositories containing 3H-benzocaine in rats.

The effects of the suppository vehicle, drug concentration, and nonionic surfactants on in vitro benzocaine dialysis through a cellulose membrane and on rectal absorption in rats of total radioactivity following administration of 3H-benzocaine were investigated. In vitro dialysis correlated quite well with in vivo absorption, and drug release was greater from water-soluble vehicles than from oleaginous vehicles. Inclusion of a nonionic hydrophilic or lipophilic surfactant in cocoa butter resulted in a statistically significant increase for in vitro drug release, while a lipophilic surfactant showed little effect in vivo and a hydrophilic surfactant depressed release in vivo. Both types of surfactant had small effects on release from polyethylene glycol. In vitro release of benzocaine from some commercially available suppositories was compared with experimental preparations. Variation in blood radioactivity following administration of the same concentration of 3H-benzocaine in the same dosage form in male and female rats is reported.

Animals↗