JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Pharmacy II Year MEDICINAL CHEMISTRY - I Previous Question Paper (April/May - 2023 - R17)

Optical isomerism occurs in molecules that possess a chiral center, allowing them to exist as non-superimposable mirror images called enantiomers. These isomers rotate the plane of plane-polarized light in opposite directions (dextrorotatory or levorotatory).

Geometrical isomerism, or cis-trans isomerism, arises in molecules with restricted rotation, such as those containing a carbon-carbon double bond. It results from different spatial arrangements of substituents around the rigid bond, where cis isomers have similar groups on the same side and trans isomers have them on opposite sides.

Drug metabolism is influenced by several physiological, chemical, and environmental factors that determine the rate and extent of biotransformation:

• Physiological Factors: Age plays a significant role, as neonates have immature enzyme systems and elderly patients often show reduced hepatic blood flow and enzyme activity. Gender differences can also occur due to hormonal influences on cytochrome P450 enzymes.
• Genetic Factors: Genetic polymorphism leads to variations in the expression of drug-metabolizing enzymes (e.g., slow vs. fast acetylators), which can result in significant differences in drug response and toxicity among individuals.
• Environmental and Dietary Factors: Enzyme induction or inhibition by other substances significantly alters metabolism. For example, cigarette smoking or consumption of cruciferous vegetables can induce specific enzymes, while certain foods or co-administered drugs can inhibit them, leading to potential drug-drug interactions.
• Pathological Factors: Diseases affecting the liver, such as cirrhosis or hepatitis, directly impair the primary site of metabolism, leading to decreased clearance and prolonged half-life of drugs.