Rx Note

Introduction Pharmacokinetics - The study of the time course of drug absorption, distribution, metabolism and excretion (ADME) . Pharmacodynamics - The relationship between drug concentration at the site of action and resulting effect, including the time course and intensity of therapeutic and adverse effects. Absorption With intravenous route, all of the administered drug is absorbed. However, if a drug is administered by any other route, it must be absorbed into the blood stream. This process may or may not be 100% efficient. Bioavailability (F) is the fraction of the administered dose which is absorbed into the bloodstream. It only estimates the extent of absorption, not take into consideration the rate of drug absorption. Factors that affect bioavailability include Inherent dissolution and absorption characteristics of the administered chemical form (e.g. salt, ester) The dosage form (e.g. tablet, capsule) The route of administration The stability of the active ingredient in the...

Introduction Tablets are widely used and generally preferred by patients for various reasons, including Ease of swallowing. Portability and compactness (in comparison to liquid formulations). Unlike injectable dosage forms , they are non-invasive and can be self-administered. The rate and extent of oral drug absorption are influenced by the Physiological factors associated with the structure and function of the gastrointestinal tract Physicochemical properties of the drug (e.g. solubility and dissolution rate) and dosage form factors In general, for oral absorption, a molecule should not violate more than one of the rules known as Lipinski's Rule of Five . The molecule should have No more than 5 hydrogen bond donors (-NH, -OH) No more than 10 hydrogen bond acceptors (-N, -O) A molecular mass less than 500 Da An octanol-water partition coefficient, log P, of not more than 5 Exceptions to the rule of 5 are those probably substrates for naturally occurring transporters, such as antib...