Chemistry Labs

Biochemistry and biomedical chemistry

Pharmacokinetics, toxicity

Pharmacokinetics follows drug exposure over time; toxicology asks how exposure relates to harmful effects.

1 Lower secondary2 Upper secondary3 Undergraduate4 Advanced5 Research

IntuitionIntuition: the central idea

Pharmacokinetics follows drug exposure over time; toxicology asks how exposure relates to harmful effects.

Explore the schematic model; it illustrates a concept rather than replacing experimental evidence.

SchoolSchool level: key concepts and a first application

Definition: Core concept

For a one-compartment IV bolus model, concentration decays exponentially. Oral absorption introduces an absorption phase; clearance and bioavailability shape exposure.

Absorption, distribution, metabolism and excretion (ADME) determine exposure. Toxicity can arise from parent drug, metabolites, off-target binding or cumulative exposure.

Key terms and meaning
TermInterpretation
Half-lifeTime for concentration to fall by half under exponential elimination.
ClearanceVolume cleared of drug per unit time.
Therapeutic windowA concentration range aiming to balance efficacy and toxicity.

Example: Apply the idea

A drug has a 6 h elimination half-life and an initial concentration of 80 mg L⁻¹. Estimate concentration after 18 h in the one-compartment model.

Solution

Eighteen hours is three half-lives, so C=80(1/2)3=10C=80(1/2)^3=10 mg L⁻¹. This estimate assumes linear, first-order elimination and a constant compartment model.

UndergraduateUniversity level: quantitative description

C(t)=C0e−kt,t1/2=ln⁡2kC(t)=C_0e^{-kt},\qquad t_{1/2}=\frac{\ln 2}{k}

Bioavailability FF scales absorbed dose reaching systemic circulation. Dose adjustments, dosing interval and clearance together set average steady-state exposure.

AdvancedAdvanced: assumptions and mechanistic detail

More realistic PK models can be multi-compartment or physiologically based; toxicology adds dose–response, time course, metabolites and organ-specific susceptibility.

ResearchResearch frontier: open questions and current practice

References