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Distribution is the reversible transfer of a drug from the bloodstream to various tissues and organs. Once absorbed, drugs distribute throughout the body, moving into different tissues and fluids. Distribution depends on: Blood Flow (Perfusion Rate) Organs with higher blood flow (brain, liver, kidneys) get drug supply more rapidly. Skeletal muscle, adipose tissue, and skin … Read more

Metabolism of drugs involves enzymatic conversion into active or inactive metabolites for easier elimination. Definition to Metabolism of drugs: It is the process by which drugs are chemically altered (usually in the liver) to make them more water-soluble for excretion. Sites: Primary: Liver (most important). Others: Kidney, lungs, intestines, plasma. Phases of Metabolism: Phase I … Read more

Enzyme induction and inhibition alter drug metabolism, affecting drug activity, duration, and interactions. Enzyme Induction: Certain drugs increase the activity of CYP450 enzymes. Leads to faster metabolism of the drug and/or other drugs. Effect: Reduced plasma levels and therapeutic effect. Examples of Enzyme Inducers: Rifampin Phenobarbital Carbamazepine Phenytoin Enzyme Inhibition: Some drugs inhibit CYP450 enzymes. … Read more

Excretion of drugs is the process of eliminating drugs and metabolites mainly via kidneys, bile, or lungs. Excretion of Drugs Excretion is the process by which the drug or its metabolites are removed from the body. Renal Excretion (most common) Glomerular Filtration: Depends on the free drug fraction in plasma (unbound drug is freely filtered). … Read more

Kinetics of drug elimination explains how drugs are removed from the body, following zero or first-order processes. Drug elimination kinetics describe how the concentration of a drug decreases over time. Clearance and Half-Life Clearance (CL): The volume of plasma completely cleared of drug per unit time (mL/min or L/hr). Total body clearance is the sum … Read more

Idiosyncrasy in pharmacology refers to an unusual and unpredictable drug reaction that is not dose-dependent and often genetically determined. Such drug responses vary among individuals, where most patients tolerate the medicine, but certain susceptible people may experience harmful effects. For example, Primaquine can cause hemolysis in individuals with G6PD deficiency, highlighting how genetic factors influence … Read more

Definition of Tolerance: It is a condition where increasing doses of a drug are required to produce the same effect previously achieved with a lower dose. Types: Pharmacokinetic: Due to increased drug metabolism (e.g., enzyme induction). Example: Barbiturates increase liver enzymes that metabolize drugs. Pharmacodynamic: Due to cellular changes at the receptor level (e.g., receptor … Read more

This article explains about the Addiction is a chronic disorder marked by compulsive drug use despite harmful consequences. Definition: Addiction is a chronic, relapsing disorder characterized by: Compulsive drug-seeking behavior Loss of control over drug use Continued use despite harm It is mainly psychological and involves reward pathways in the brain (dopamine system). Drugs Commonly … Read more

Tachyphylaxis is a rapid decrease in drug response after repeated doses in a short period, leading to reduced effectiveness. Definition of Tachyphylaxis: Tachyphylaxis is a rapid decrease in drug response after repeated administration in a short time. Key Features: Occurs quickly (within minutes to hours). Further dosing does not restore the effect. Mechanism: Possible depletion … Read more

Dependence is a condition in which the body adapts to continuous drug use, making the substance necessary to maintain normal physiological or psychological function. When the drug is reduced or stopped, withdrawal symptoms such as anxiety, irritability, sweating, tremors, or more severe reactions may occur. It can be physical, where the body relies on the … Read more