Dose-response relationship: irrespective of how the effect of a drug is produced, through binding to the receptor or through chemical interactions, the concentration of the drug at the site of action controls its effect

However, the concentration response can be complex and often non-linear.

The relationship between the dose of the drug, regardless of the route of administration, and its concentration at the cellular level is even more complex.

The dose-response curve is typically represented as a dose or function of dose (e.g. log10 of dose) on the X-axis and as a measure of effect (response) on the Y-axis.

Since a drug effect is a function of both dose and time, such a graph describes the dose-response relationship independently of time

To measure pharmacological effects, those obtained at peak or steady-state conditions (e.g. during continuous EV infusion) are frequently considered.

Pharmacological effects may be quantified at the molecular, cellular, tissue, organ, apparatus or whole microorganism level.

A hypothetical dose-response curve has characteristics that vary:

• Potency (position of the curve along the dose axis)
• Maximum efficacy or ceiling effect (maximum achievable response)
• Tilt (variation in response per unit dose)

Biological variation also occurs (variation in the intensity of the response between individuals in the same population who have been given the same dose of drug).

Plotting dose-response curves for drugs that are studied under the same conditions can help to compare drug profiles.

This information helps to determine the dose required to achieve the desired effect.

The dose-response relationship, which involves the principles of pharmacokinetics and pharmacodynamics, determines the dose required, the frequency of administration as well as the therapeutic index of a drug in a population.

The therapeutic index (the ratio of the lowest toxic concentration to the median of the therapeutic concentrations) helps determine the efficacy and safety of a drug.

Increasing the dose of a drug with a low therapeutic index increases the likelihood of toxicity or ineffectiveness of the drug.

However, these characteristics differ across populations and are influenced by patient-related factors such as pregnancy, age and organ function (e.g. estimated glomerular filtration rate).

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Source:

MSD