Physiology

ANS Pharmacology: Cholinergic Transmission and Receptor Types

admin2 days ago018 mins

Introduction / Overview Cholinergic transmission constitutes a fundamental component of the autonomic nervous system (ANS), mediating a wide array of physiological processes ranging from heart rate modulation to gastrointestinal motility. The neurotransmitter acetylcholine (ACh) is released from pre‑ganglionic sympathetic, post‑ganglionic sympathetic, and parasympathetic neurons, acting on both nicotinic (nAChR) and muscarinic (mAChR) receptor families. A…

Physiology

Pharmacodynamics: Signal Transduction Pathways and Receptor Regulation

admin2 days ago020 mins

Introduction Pharmacodynamics refers to the study of the biochemical and physiological effects of drugs on the body and the mechanisms through which these effects are produced. Central to this discipline is the concept of signal transduction, the cascade of molecular events initiated by drug–receptor interactions that ultimately lead to a cellular response. Historically, the elucidation…

Clinical

Pharmacodynamics: Dose-Response Relationships, Potency, Efficacy, and Therapeutic Index

admin2 days ago018 mins

Introduction Pharmacodynamics refers to the study of the biochemical and physiological effects of drugs on the body, and the mechanisms by which these effects are produced. Historically, the term emerged in the late 19th and early 20th centuries as researchers sought to quantify how drugs interacted with biological systems. Early investigations by scientists such as…

Pharmacology

Pharmacodynamics: Agonists, Antagonists, and Inverse Agonists

admin2 days ago017 mins

Introduction Pharmacodynamics concerns the relationship between drug concentration at the site of action and the resulting effect. Core to this field is the classification of ligands based on their interaction with receptors: agonists, antagonists, and inverse agonists. These distinctions are essential for understanding drug efficacy, potency, and therapeutic index, as well as predicting clinical outcomes…

Physiology

Pharmacodynamics: Mechanism of drug action and receptor families

admin2 days ago017 mins

Introduction Definition and Overview Pharmacodynamics (PD) encompasses the study of the biochemical and physiological effects of drugs, as well as the mechanisms by which drugs exert their actions on biological systems. The field integrates concepts from molecular biology, physiology, and chemistry to explain how a compound interacts with its target, influencing cellular function and ultimately…

Pharmacokinetics

Pharmacokinetics: Steady-State Concentration, Loading Dose, and Maintenance Dose Calculations

admin2 days ago017 mins

Introduction Definition and Overview Pharmacokinetics is concerned with the movement of drugs through the body, encompassing absorption, distribution, metabolism, and excretion (ADME). Within this framework, steady-state concentration, loading dose, and maintenance dose calculations constitute essential tools for achieving therapeutic drug levels while minimizing toxicity. Steady-state concentration refers to the equilibrium reached when the rate of…

Pharmacokinetics

Pharmacokinetics: Renal Clearance, Elimination Kinetics, and Half‑Life

admin2 days ago019 mins

Introduction Definition and Overview Pharmacokinetics describes the movement of drugs within the body, encompassing absorption, distribution, metabolism, and excretion (ADME). In particular, renal clearance, elimination kinetics, and half‑life constitute core components that determine how long a drug remains effective and at what concentration it exerts therapeutic or adverse effects. Renal clearance refers to the volume…

Pharmacokinetics

Pharmacokinetics: Enzyme Induction and Inhibition Interactions

admin2 days ago014 mins

Introduction Definition and Overview Enzyme induction and inhibition refer to the modulation of drug-metabolizing enzymes, most notably those of the cytochrome P450 (CYP) superfamily, by exogenous or endogenous agents. Induction enhances enzyme expression or activity, accelerating drug clearance, whereas inhibition reduces enzyme function, prolonging systemic exposure. These interactions are pivotal in determining the pharmacokinetic profile…

Pharmacokinetics

Pharmacokinetics: Phase I and Phase II Biotransformation Reactions

admin2 days ago017 mins

Introduction Biotransformation refers to the enzymatic modification of xenobiotics within the body to enhance solubility and facilitate excretion. Two sequential stages, traditionally termed Phase I and Phase II reactions, constitute the core of drug metabolism. Phase I reactions typically introduce or expose functional groups through oxidation, reduction, or hydrolysis, whereas Phase II reactions conjugate these functional groups with endogenous…

Pharmacokinetics

Pharmacokinetics: Volume of Distribution and Plasma Protein Binding

admin2 days ago016 mins

Introduction Definition and Overview Volume of distribution (Vd) and plasma protein binding (PPB) are foundational parameters that shape the disposition of drugs within the human body. Vd serves as a theoretical construct that relates the total amount of drug in the body to the concentration observed in plasma. PPB, on the other hand, quantifies the…