The effect of a drug varies according to different factors. Patients taking the same medicine and same dose experience varying effects of the drug from person to person. This variation occurs because individuals have different pharmacokinetic parameters, including variations in the number of receptors and coupling of proteins, as well as differences in hormonal tone or the concentration of specific constituents.
Factors that modify drug actions can be categorized as follows:
Quantitatively – The plasma concentration of the drug or the drug’s action is either increased or decreased. These adjustments are made to the drug dosage.
Qualitatively – The type of response is altered, as in cases of drug allergies. However, this is not common.
Various factors affecting drug actions include:
- Body size
- Age
- Sex
- Species and race
- Genetics
- Route of administration
- Environmental factors
- Time of administration
- Psychological factors
- Pathological states
- Cumulation
- Tolerance
- Other factors
