INTRODUCTION TO BIOPHARMACEUTICS AND PHARMACOKINETICS
Wednesday, March 30, 2011 - 14:00
Biopharmaceutics is the study which shows how the drug absorption rate is affected by various factors like physical and chemical properties of the drug, the dose form of the drug and the route through which the drug is administered. (1) It includes the study of the following: (2) 1. The stability of the drug 2. The liberation of the API from the dosage form 3. The rate at which the drug is getting converted into solution 4. And finally the absorption of the drug into the systemic circulation It includes the study of various tests that have took place in the laboratory and in the animals.(2) Pharmacokinetics: "Pharmacokinetics is defined as the study of rate processes involved in absorption, distribution, metabolism and excretion"(2) It will decide the how much drug should to be given to the patient, and the route through which the drug must be administered, the time taken by the drug to start its action, and how long the drug ction will remain. (3) Absorption is the movement of the drug into the systemic circulation from where the drug has been delivered. Once its absorbed it will move to the other parts of the body which is called distribution. Metabolism is the phenomenon of the chemical changes that drug undergo within the body. Excretion is the moving out of the drug from the body. (3) APPLICATIONS (2) Biopharmaceutics 1. If a company is trying to develop the new dosage form and when it is given to the human beings, in some cases the drug may release very slowly. Or else the entire drug may be released one at a time. Both the conditions are not required. To obtain the required action, the exact formulation can be obtained by using the principles of biopharmaceutics. 2. If a company tries to change the ingredients of the tablet dosage forms. FDA will approve the change only if the bioavailability is equal to the initial formulation and the bioavailability can be studied by the principles of biopharmaceutics. 3. Similarly if there is tablet dosage form of the drug and if the company tries to release the drug in the form of transdermal route, the bioavailability is compared and will be only released if the bioavailability is similar. Pharmacokinetics 1. The pharmacokinetics equations are very much useful in the determination of bioavailability. 2. How many times the drugs should be given to the patient can be determined by pharmacokinetics principles. 3. In case of controlled release dosage forms, how much drug should be given can be determined by pharmacokinetics principles. 4. In the patients whose kidney got failed, the amount of the drug that should be administered can be calculated by using pharmacokinetics. Here the drug elimination will be less. Reference: 1. Pharmaceutics The science of Dosage form Design edited by Aulton, second edition, Churchill livingstone publishers, page no 213 2. http://4my8383.blogspot.com/ (accessed on 25th march 2011) 3. Essentials of Medical pharmacology by KD Tripathi, 5th edition, Jaypee publishers, page no 11, 14, 16, 20, 25. "This blog does not contain any plagiarized material"