Biomedical subjects

K P Shah

Publications and source records attributed to K P Shah.

18 recordsLinked to original sources

PubMed1995

Automated analytical systems for drug development studies. 3. Multivessel dissolution testing system based on microdialysis sampling.

An automated system consisting of a six-vessel dissolution apparatus, microdialysis sampling, STT E6 multiposition switching valve and a liquid chromatograph was assembled to measure dissolution profiles of immediate and sustained-release tablets. A DL-5 microdialysis loop probe (BAS, Inc.) was immersed in each dissolution vessel and perfused with a suitable medium for sampling. The dialystate from each vessel was injected sequentially onto an on-line liquid chromatography (LC) system for automated analysis. The STT E6 multiposition switching valve was used to sample up to six vessels simultaneously. After addressing issues related to sample carry-over and between-probe variability, the automated system was used in a reproducible manner (RSD < 3%) to measure the dissolution of immediate-release acetaminophen tablets and Accutrim (containing 75 mg phenylpropanolamine HCl) 16 h Precision Release tablets. An uneven injection time sequence was used to monitor three acetaminophen tablets per dissolution run using the automated system and each vessel was sampled about every 6.5 min. However, with Accutrim 16 h Precision Release tablets, a longer sampling interval (10 min) was used, the six tablets could be tested in each dissolution run. The dissolution profiles of acetaminophen and Accutrim tablets measured using the automated multivessel dissolution system compared well with manual and automated single-vessel dissolution systems.

Acetaminophen↗

PubMed1994

Automated analytical systems for drug development studies. II--A system for dissolution testing.

Microdialysis is a non-equilibrium dynamic sampling method in which the analytes diffuse across a semipermeable membrane due to a concentration gradient and are carried away by the constantly pumping perfusion medium for on-line analysis. A BAS, Inc. microinfusion pump/injector and an on-line LC system were interfaced with a dissolution apparatus to automate dissolution testing of tablets. A DL-5 microdialysis loop probe was suspended in the dissolution medium for sampling. The automated system was used reproducibly (RSD < 2%) to measure the dissolution of acetaminophen and Sulfatrim tablets. Drug recovery from the microdialysis probe was a function of the perfusion rate at constant temperature. However, microdialysis recovery was independent of drug concentration over the linear ranges of the assays for the analytes of interest. Dissolution profiles determined by microdialysis sampling were compared with manual sampling. Identical profiles were obtained for acetaminophen tablets in water at 37 degrees C and 50 rpm by both sampling methods. Dissolution of Sulfatrim tablets was determined in 0.1 M hydrochloride acid at 37 degrees C and 75 rpm. Microdialysis sampling permitted the use of a specially designed perfusion medium to buffer the acidic samples before injecting onto the LC column. Dissolution profiles of sulphamethoxazole were comparable for both sampling methods; however, microdialysis sampling indicated slightly higher release of trimethoprim from the Sulfatrim tablets, which was attributed to release of adsorbed drug from the connecting tubing.

Acetaminophen↗

PubMed1994

Automated analytical systems for drug development studies. I--A system for the determination of drug stability.

An automated system consisting of a pH-stat, microdialysis sampling and a liquid chromatograph was assembled to measure the rate of rapid chemical reactions. 2',3',5'-Triacetyl-6-azauridine was used as a model compound to validate the performance of the automated system. Buffer catalysis was minimized by using a non-catalytic concentration of borate buffer along with a pH-stat to maintain the pH during the kinetic run. The microdialysis sampling technique permitted sample quenching and buffering of the solutions to a pH compatible with the LC column materials. The combination of microdialysis sampling and rapid LC analysis allowed reactions with a half-life of approximately 1 min to be sampled every 30 s. The rates of hydrolysis of the drug, measured at different conditions of temperature (37-70 degrees C) and pH (9.0-10.5) using the automated system, compared well with the previously determined values.

Autoanalysis↗

PubMed1991

Stability of diltiazem in acid solution.

A brief study of the stability of diltiazem was conducted at 70 degrees C in the pH range of 0.45 to 6.1 using polarimetry. Racemization did not occur. The hydrolysis rate of the acetate ester moiety was found to be slow, with a minimum in the pH-rate catenary at approximately pH 3.5. Where reaction products are known, photoelectric polarimetry has great advantages in speed, convenience, and cost compared with chromatographic methods for measuring rates of reaction of optically active analytes.

Diltiazem↗

PubMed1990

Risk factors for birth asphyxia and brain damage in pregnancy and labour.

In this review the patho-physiology and risk factors of birth asphyxia are discussed. Simple and appropriate, but scientifically sound, technology for the prevention of birth asphyxia is described. This can be used at home, in the community, in health sub-centres and health centres to identify and assess risk factors so that appropriate referral can be made. Based on experience in developing countries, actions which can be performed by the mother, relatives, neighbours, traditional birth attendants and nurses and midwives are described.

Asphyxia Neonatorum↗

PubMed1988