Absorption of Drugs

Absorption of Drugs

Absorption of Drugs refers to the process by which a drug enters the bloodstream from its site of administration. Factors Affecting Absorption: Route of Administration: Oral, IV, IM, subcutaneous, transdermal, inhalational, etc. IV route bypasses absorption as the drug is delivered directly into the bloodstream. Physicochemical Properties of the Drug: Solubility (lipid vs. water solubility) … Read more

Allergy (Drug Hypersensitivity)

Allergy (Drug Hypersensitivity)

Allergy (Drug Hypersensitivity) is an abnormal immune reaction to a drug, causing effects like rash, swelling, or anaphylaxis. Definition of Drug Hypersensitivity: A drug allergy is an immune system-mediated adverse drug reaction. It can occur at low doses, is unpredictable, and is not related to the pharmacologic action of the drug. Types of Hypersensitivity Reactions … Read more

Distribution of Drugs

Distribution of Drugs

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 (Biotransformation) of Drugs

Metabolism (Biotransformation) of Drugs

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

Enzyme Induction and Inhibition

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

Excretion of Drugs

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

Kinetics of Drug Elimination

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

Idiosyncrasy

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

Tolerance

Tolerance

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

Addiction

Addiction

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