The frequency (dosing interval) and dose at which a drug is to be administered.

The dosing regimen is based upon exposure-bacterial response relationships (see dose finding). Dose and duration of therapy can influence the likelihood of selecting drug-resistant mutants due to suboptimal exposure. Many factors are taken into consideration to determine the optimal regimen. This includes age, sex, ethnicity, other drugs (DDI) and patient health status (kidney/liver function).

See also dose fractionation study.