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Dose, Exposure and Response
The amount of medicine given influences exposure, but the resulting benefits and adverse effects also depend on how the body handles and responds to it.
#Dose and concentration are different parts of the story
NIGMS describes a dose entering by a particular route and then being absorbed, distributed, metabolised and excreted. Bioavailability concerns how much of an administered dose reaches the blood. The MSD professional account distinguishes the administered dose from concentration at the site where the drug acts.
The amount given is not a direct measurement of how much reaches every target or how long it stays there. Route, formulation and the body's handling of the medicine are part of the explanation. This page does not calculate exposure or compare doses for an individual.
Evidence: NIGMS: what happens to medicine in your body / MSD Manual: dose-response relationships
#A response need not rise in a straight line
MSD explains that the relationship between concentration and effect can be complex and nonlinear. Its dose-response curves distinguish potency, the position along the dose axis, from maximal effect, the greatest response attainable in that measurement. It also notes variation between people given the same dose.
A larger dose does not mean proportionally greater benefit, and greater potency is not the same as a greater maximum effect. A curve depends on the effect measured and the study conditions. It is not a dosing chart or a reason to increase a prescribed amount.
Evidence: MSD Manual: dose-response relationships
#Benefit and harm constrain how a medicine is used
NIGMS describes studying desired and unwanted responses across doses to guide the therapeutic window. MSD warns that increasing the dose of a drug with a narrow therapeutic index can increase toxicity risk, with effects influenced by factors such as age and organ function. These concepts describe the balance considered in medicine use; they do not guarantee a harm-free range.
Follow the actual product and prescriber's instructions, and ask the prescriber or pharmacist about any unclear dose or schedule. This explainer supplies no dose, safe range, missed-dose rule or monitoring plan and cannot be used to change one.
Evidence: NIGMS: how medicines work / MSD Manual: dose-response relationships / FDA: drug interactions
Source note
The sections above were checked against the linked sources. No clinical review has been performed. This is general research education, not a clinical guideline.