by Falguni Khanderiya
One or more of the following categories of differences among the individuals responsible for variation:-
- individuals differ in pharmacokinetic handling of drugs.
- variation in number or state of receptors.
- variation in neurogenic concentration of specific constituents.
Factors modifying drug action either
1. Quantitatively-depend on plasma concentration
2. Qualitatively-depend on drug allergy or idiosyncrasy.
Various factors are:-
1. Body size-
Individual dose=BW (kg)/70 * avg adult dose
Dose of drug for children is calculated from adult dose.
Child dose=age/age+12 *adult dose
Some drugs of low safety margin when given in higher concentration cause kernictrus (sulfa) ,/Chloramphenicol may produce gray baby syndrome.
Females have lower body size and require less dose.
Gynaecomastia is a side effect that occurs only in men.
4. SPECIES AND RACE-
Black race requires higher and Mongols require lower concentration of atropine to dilate the pupil.
5. GENETICS-the effect of genetic factors can also vary the response of a drug (pharmacokinetics)
6. ROUTES OF ADMINISTRATION-
Speed and intensity of drug depends on route of drug especially in i.v. and sublingual.
7. ENVIRONMENTAL FACTORS AND TIME OF ADMINISTRATION
8. PSYCHOLOGICAL FACTORS-placebo
9.PATHOLOGICAL STATES-like liver diseases, Kidney diseases, GIT diseases, Congestive heart failure can also alter the response of a drug
10.OTHER DRUGS- given simultaneously can change the response.
Depending on pharmacokinetics and pharmacodynamics of the drugs.
11.CUMULATION-long term administration of a drug can also alter the response.
Depends on higher drug dose called as refractoriness.
It is of 2 types-
Natural-in it some individuals are less sensitive to a particular drug.
Acquired-if the patient is given same drug repeatedly for long time,tolerance is developed