Kinetics of thermal decomposition of buspirone hydrochloride in solid state.

Stability of buspirone hydrochloride (BH) in solid state has been studied. The content of BH and changes in its concentration during preliminary kinetic studies of the stability of this drug in BUSPAR tablets and in substance were assessed by spectrophotometry in UV, after previous chromatographic separation lambda max = 239 nm (A1%1 cm = 502 in 50% aqueous methanol solution). Using thin layer chromatography several breakdown of buspirone were detected.

[Effect of chemical structure of various penicillins on the stability of beta-lactam group in their molecules. VI. Effects of relative humidity and heat on the stability of amoxicillin trihydrate and amoxicillin sodium in the solid phase]. / Wplyw charakteru chemicznego niektórych penicylin na trwalosc ugrupowania beta-laktamowego w ich czasteczce. VI. Badanie wplywu wilgotnosci wzglednej i podwyzszonej temperatury na trwalosc trójwodzianu i soli sodowej amoksycyliny w fazie stalej.

Dependence of stability of Amoxycillin trihydrate (AMOXY. 3H2O) and Amoxycillin-Natrium (AMOXY-Na) upon relative humidity (RH) and temperature was investigated using the iodometric method for the determination of Amoxycillin. The first order rate constants and activation parameters have been determined at controlled moisture conditions. The straightline relationship lg k = f(RH) at T = const. has been stated, which however is fulfilled by AMOXY-Na only at RH greater than or equal to 50%. The calculated factors of the equation lg k = a + b.1/T + c.RH proved to enable estimation of the stability of the studied antibiotics at any climate conditions. The performed kinetic studies have shown that AMOXY-Na undergoes degradation about 1.5 x 10(3) times faster than AMOXY.3H2O, at RH greater than or equal to 50%.

The effect of the chemical character of certain penicillins on the resistance of the beta-lactam group in their molecules. Part 5: Kinetics of thermal decomposition in solid state.

The decomposition rate at elevated temperature was studied of the following penicillins: ampicillin trihydrate (1), 6-aminopenicillanic acid (2; 6-APA), amoxicillin trihydrate (3), piperacillin (4), amoxicillin sodium (5), azlocillin sodium (6), mezlocillin sodium monohydrate (7) and azidocillin sodium (8). The pattern of decomposition was found to comply with the first-order reaction. The thermal stability of the compounds at 25 degrees C increased in accordance with the sequence 1 less than 2 less than 3 much less than 6 less than 5 less than 8 less then 7 much less than 4, which was connected with the hydrophilic and lipophilic properties of these penicillins. An isokinetic enthalpy-entrophy correlation was demonstrated. The calculated beta value was 420 K.

Kinetics of drug decomposition. Part 62. Kinetics of penicillin G potassium salt (PGP) thermal degradation in solid phase.

The kinetics of degradation of penicillin G K salt (PGP) in solid phase in the temperature range 70-140 degrees C were investigated. The obtained sigmoidal curves were interpreted in terms of the Prout-Tompkins kinetics. The appropriate mathematical equations were derived for the induction and acceleration periods which enable to calculate the degradation half-time, t0.1 value and the induction time (t'). The Arrhenius plot shows the isokinetic point where the rates of reaction for both periods are identical.

Kinetics of drug decomposition. Part 45. Logk--pH profile for rolitetracycline degradation.

UV spectrophotometry and fluorometry were applied for an examination of rolitetracycline (RT) degradation at pH's ranged from ca 0-8 to 13-0. It was demonstrated that these methods enable to follow the rate of degradation of tetracycline formed in the course of RT hydrolysis. However, they do not allow to monitor the hydrolysis of RT to tetracycline. Application of the so-called "subtraction technique" permits to calculate the rate constants for the total, reversible epimerization reaction and for the subsequent degradation of the resultant products. A rate equation derived for RT degradation in an alkaline medium beginning at pH 10-5 contains a term second-order in the hydroxide ion. Such a relationship was not yet observed in the course of an antibiotic degradation.

Kinetics of drug decomposition. Part 48. Specific acid-base hydrolysis of rolitetracycline.

Using chromatographic-spectrophotometric method, the effect of H+ and OH- ions on the rate of hydrolysis of rolitetracycline (RT) to tetracycline (T) at 20degreeC was investigated. The advantage of this analytical procedure over the direct fluorescence or UV absorption measurements of RT solutions during the kinetic investigations in HCl medium was demonstrated. The catalytic rate constants (kH+ and kOH-) for the hydrolytic degradation of RT under oxygen-free conditions are given.