Pharmacokinetics
A free course for medical, pharmacy and nursing students who want a working grasp of how the body handles drugs. It covers absorption, distribution, metabolism and excretion, then clearance, volume of distribution, half-life and bioavailability, and applies them to concentration-time curves, steady state, loading and maintenance doses, and dose adjustment when renal or hepatic function changes.
About this course
Pharmacokinetics: Principles and Clinical Application
Pharmacokinetics describes what the body does to a drug. This course establishes a working knowledge of the four fundamental processes — absorption, distribution, metabolism, and excretion — and then applies these principles to clinical decision-making. Rather than memorising isolated values, learners build a mental model of how a drug moves through the body and how that movement predicts the drug's effect over time.
Introduction to Pharmacokinetics
The course begins by defining the core concepts and the mathematical language used to describe drug movement. You will examine key parameters including clearance, volume of distribution, half-life, and bioavailability. Emphasis is placed on understanding how these parameters relate to one another and how they describe the shape of a concentration-time curve. Through worked examples, you will learn to interpret a simple pharmacokinetic profile and extract clinically meaningful information from it.
Absorption
This section explores the routes by which a drug enters the systemic circulation. You will consider the factors that influence the rate and extent of absorption, including physicochemical properties of the drug, formulation, route of administration, and physiological variables such as gastric emptying and intestinal blood flow. The concept of bioavailability is introduced, with a discussion of first-pass metabolism and how enteral and parenteral routes differ in their delivery of drug to the site of action.
Distribution
Once a drug is in the circulation, it distributes into body tissues. This section covers the major factors governing distribution: plasma protein binding, tissue perfusion, and the physicochemical nature of the drug, particularly its lipophilicity and ionisation state. The concept of volume of distribution is explained as a proportionality constant rather than a physical space. Clinical consequences of altered distribution are highlighted, including the effect of hypoalbuminaemia on free drug concentrations and the potential implications for highly protein-bound drugs such as warfarin.
Metabolism
Drug metabolism, or biotransformation, is the principal mechanism for terminating drug action and preparing molecules for elimination. The course describes the main phases of metabolism and the role of the cytochrome P450 enzyme system in oxidative metabolism. You will learn how enzyme induction and inhibition can alter drug exposure, how genetic polymorphisms contribute to inter-individual variability, and how metabolism may produce active or toxic metabolites. Examples are used to illustrate these concepts, including the metabolism of paracetamol and the activation of certain prodrugs.
Excretion
This section focuses on the elimination of drugs and their metabolites from the body. Renal excretion is covered in detail, including the processes of glomerular filtration, tubular reabsorption, and tubular secretion. The concept of clearance is examined as the physiological basis for maintenance dosing. The course also considers non-renal routes of elimination and the impact of impaired renal function on drug accumulation.
Clinical Pharmacokinetics
The final section brings the principles together in a practical, patient-focused context. You will apply pharmacokinetic concepts to interpret concentration-time data from therapeutic drug monitoring. This includes the use of steady-state concentrations and trough levels to individualise therapy for drugs such as gentamicin and digoxin. The course considers how changes in renal or hepatic function, age, pregnancy, and interacting medicines influence dosing decisions, and how to estimate drug accumulation when a patient's organ function is altered. Throughout, a cautious approach is taken to dosing in special populations, recognising that the practice varies by region and formulary.
The course is delivered through explanatory text and clinical examples that demonstrate how to use a pharmacokinetic profile to inform a dosing decision. Worked calculations are provided throughout, and learners are encouraged to practise these to build confidence.
This course suits medical, pharmacy, and nursing students who require a solid foundation in pharmacology, as well as practising clinicians and pharmacists who wish to refresh their understanding of drug handling. No prior advanced mathematics is required; the principles are taught using simple arithmetic and straightforward reasoning. The focus throughout is on the application of pharmacokinetic principles to safe and rational prescribing.
Curriculum
5 modules · 20 lessons
Covers fundamental concepts of drug disposition in the body, including the ADME framework and the significance of pharmacokinetics in clinical practice.
- 20 minDefining Pharmacokinetics
This lesson defines pharmacokinetics and its scope. It contrasts pharmacokinetics with pharmacodynamics and introduces the principal processes affecting drug concentrations.
- 20 minThe ADME Framework
This lesson introduces the ADME framework: absorption, distribution, metabolism and excretion. These four processes work sequentially to determine the plasma concentration and tissue exposure of a drug.
- 20 minThe Concentration-Time Curve
This lesson examines the plasma concentration-time curve, a fundamental tool in pharmacokinetics. It explains how the curve reflects drug absorption, distribution and elimination, and how area under the curve relates to drug exposure.
- 20 minClinical Importance of Pharmacokinetics
This lesson explains why pharmacokinetics is essential for clinical decision-making. It covers the impact of patient variability, the need for individualised dosing, and the role of therapeutic drug monitoring.
Explores the processes of drug absorption from various routes, factors influencing absorption, and the concept of bioavailability with first-pass metabolism.
- 30 minMechanisms of Drug Absorption
Covers the passive and active transport processes by which drugs cross cell membranes, including diffusion, facilitated transport, and efflux transporters.
- 45 minRoutes of Administration and Absorption
Compares intravenous, oral, intramuscular, subcutaneous, and other routes in terms of absorption rate and extent, highlighting advantages and limitations for clinical use.
- 30 minFactors Influencing Drug Absorption
Examines physicochemical properties of the drug, formulation, and physiological factors such as gastric emptying, pH, and blood flow that determine absorption efficiency.
- 30 minBioavailability and First-Pass Metabolism
Defines absolute and relative bioavailability, and explains how hepatic and intestinal first-pass metabolism reduces the amount of unchanged drug reaching systemic circulation.
Examines how drugs distribute into tissues and compartments, the role of protein binding, and the clinical relevance of volume of distribution.
- 30 minDistribution into Body Compartments
Explores how drugs move from the bloodstream into various body compartments, including vascular, extracellular, and intracellular spaces. Discusses the influence of blood flow, tissue permeability, and physicochemical properties on distribution.
- 45 minPlasma Protein Binding of Drugs
Examines the binding of drugs to plasma proteins such as albumin and alpha-1 acid glycoprotein, the relationship between free and bound fractions, and the clinical consequences of altered binding.
- 30 minVolume of Distribution: Concept and Calculation
Defines volume of distribution (Vd) and explains its calculation from dose and plasma concentration. Interprets large versus small Vd values in relation to distribution into tissues.
- 45 minClinical Relevance of Volume of Distribution
Applies the Vd concept to clinical practice, including loading dose calculations and the impact of disease states on distribution. Highlights how Vd influences the interpretation of plasma concentrations.
Discusses biotransformation pathways, including phase I and II reactions, and the mechanisms of drug elimination by hepatic and renal clearance.
- 45 minPhase I Biotransformation: Oxidation, Reduction, and Hydrolysis
Explores the main phase I reactions that introduce functional groups to lipophilic drugs, with emphasis on cytochrome P450 enzymes and their role in drug metabolism.
- 30 minPhase II Conjugation Reactions and Drug Metabolites
Covers conjugation pathways such as glucuronidation, sulfation, and acetylation, explaining how they increase polarity and facilitate excretion of metabolites.
- 30 minHepatic Clearance and First-Pass Metabolism
Examines the factors influencing hepatic clearance including blood flow and intrinsic enzyme activity, and describes the clinical impact of first-pass metabolism on oral bioavailability.
- 45 minRenal Excretion of Drugs: Filtration, Secretion, and Reabsorption
Details the mechanisms of renal drug elimination, including glomerular filtration, tubular secretion, and passive reabsorption, and how they determine renal clearance.
Applies pharmacokinetic concepts to calculate half-life, clearance, and steady-state concentrations, and explains how these guide dosing regimens.
- 30 minHalf-life and the elimination rate constant
Define half-life as the time for plasma concentration to halve, and calculate it from the elimination rate constant. Explain its role in determining the duration of drug action.
- 30 minClearance: calculation and clinical implications
Explain clearance as the volume of blood cleared of drug per unit time. Calculate clearance from dose and area under the concentration-time curve, and discuss its importance in maintenance dosing.
- 40 minSteady-state concentrations and accumulation
Describe how repeated dosing leads to steady-state, and calculate the average steady-state concentration and accumulation factor. Highlight the time to reach steady-state and its relevance for therapy monitoring.
- 60 minDesigning dosing regimens: loading and maintenance doses
Apply half-life and clearance to determine loading and maintenance doses for a target concentration. Discuss the choice of dosing interval and its effects on peak and trough levels.
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