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B Knitter

Publications and source records attributed to B Knitter.

11 recordsLinked to original sources
PubMed1981

Kinetics of drug decomposition. Part 66. Kinetics of the hydrolysis of carphecillin in aqueous solution.

The rates of hydrolysis of the beta-lactam ring in the pH range 1.77--9.22 at 294, 303, 313 and 233 K and of the ester bond in the pH range 0.43--8.78 at 273, 283, 294, 303, 313 and 323 K for carphecillin have been investigated. The rate constants were determined for the reactions catalyzed by H+ and OH- ions and moreover for the hydrolysis of the beta-lactam ring catalyzed by undissociated acids and anionic bases. The thermodynamic parameters were calculated for particular reactions. In the acidic medium carphecillin is significantly more stable than carbenicillin. In the alkaline medium the rate of inactivation of carphecillin and carbenicillin is the same because carbenicillin is formed from carphecillin as the result of the very fast hydrolysis of the ester bond.

Carbenicillin↗
PubMed1978

Kinetics of drug degradation. Part 58: a method of preparation and the stability of 3% aqueous indometacin solution.

A method was worked out which allows one to obtain 3% aqueous indometacin solution. The above can be done by solubilization of indometacin by means of ethyl carbamate and ethylurea in the concentration of 30% each and boiling the mixture for 30 s. The stability of indometacin in the above solution was checked with respect to elevated temperatures and exaggerated UV light conditions and compared with the stability of the same solution but without the solubilizing agents. It appears that the solubilizing agents diminish both the hydrolytic as well as the photochemical degradation processes of indometacin. 3% aqueous indometacin solution is stable for 25 months at 20 degrees C, and it is practically non-susceptible to the effects of diffused light for many years. The indometacin solution proposed shows low acidity (pH = 6.95). It is believed that the above solution can be introduced to everyday medical treatment.

Biological Availability↗
PubMed1977

Kinetics of drug decomposition Part 51: Kinetics of indometacine photodegradation.

Indometacine aqueous solution degradation was studied under the influence of UV light. Spectrophotometric readings of absorbances at lambdamax = 270 nm were taken in order to follow changes of the indometacine solutions as a function of irradiation time. It was found that the degradation of indometacine under influence of UV light proceeds according a sequential reaction A k2 leads to B k2 leads to C k3 leads to D in which each individual step is a zero-order process Individual zero-order rate constants were calculated for indomatacine photodegradation under anaerobic and aerobic conditions. They indicate the first step (A leads to B) to be oxygen independent and the other processes (B leads to C leads to D) to be oxygen catalyzed.

Aerobiosis↗
PubMedDate not supplied

Kinetics of drug decomposition. Part 50: Graphic method for calculation of zero-order rate constants of sequential reaction of indometacine photodegradation.

Calculation of partial zero-order rate constants for a sequential reaction was presented following indometacine photochemical degradation according to the equation A k1 leads to B k2 leads to C k3 leads to D. When zero-order rate constants k1 not equal to k2 not equal to k3 and absorptivity coefficients a not equal to b not equal to c not equal to d, then individuell zero-order rate constants can be obtained from simple equations: k1 = [A]0/tA, k2 = [A]0/tB, k3 = [A]0/tC, where [A]0 is the initial concentration of a substrate, and tA, tB, tC are the starting times of the steps of the sequential reaction, which can be read from the plots for a relationship A = f(t).

Drug Stability↗
PubMedDate not supplied

Kinetics of drug decomposition. Part 67. Kinetics of degradation of dicloxacillin in aqueous solution.

The rates of hydrolysis of beta-lactam ring of dicloxacillin (DC) in the pH range 1.10-9.65 at 293, 303 and 313 K were determined. Specific rate constants were calculated for: H degree ions, undissociated phosphoric acid and H2PO4- ions catalysis of hydrolysis of undissociated DC molecule; for H+, OH-, HPO4(-2) and CH3COO- ions and undissociated phosphoric and acetic acids catalysis of hydrolysis of dissociated DC species and spontaneous hydrolysis of dissociated DC species. For each process the thermodynamic parameters were determined.

Dicloxacillin↗
PubMedDate not supplied

Kinetics of drug decomposition. Part 61. Kinetics of various ampicillin forms degradation in solid phase.

Ampicillin sodium salt degradation in solid state relies on a sequential reaction consisting of three pseudo first-order processes. The above salt is much more susceptible to degradation than acidic forms of ampicillin. The anhydrous acidic form of ampicillin is very stable in solid phase. Therefore, it can be recomended to be formulated in peroral ampicillin pharmaceutical preparations. Ampicillin trihydrate, now used in pharmaceutical formulations, is less stable than the last mentioned compound. It degrades according to Prout-Tompkins' model.

Ampicillin↗