There several different variables that may affect how the drugs act and what it will do to a human body. Majority of drugs mimic or inhibit normal physiological processes that inhibits pathological processes in the body. The following can inhibit or heighten the effect of any given drug.
Dosage
Dosage is the amount to be given at a time. It is the regulation of the frequency, size, and number of doses. Dosage is a major determinant of drug action and responses both therapeutic and adverse. This includes both the amount of drug and the frequency of administration.
Toxic doses are doses that produce signs and symptoms of toxicity while, lethal doses are the ones that cause death.
Route of Administration
This affects drug actions and response largely by influencing absorption and distribution.
Drug-Diet Interactions
Food slows absorption of oral drugs by slowing gastric emptying time and altering Gastrointestinal secretions and motility. This then makes the drugs to dissolve and deliver to absorptive sites more slowly. It can also form and insoluble drug-food complex.
Drug-Drug Interaction
The action of a particular drug may be increased or decreased by its interaction with another drug in the body.
Interactions that can increase the therapeutic or adverse effect of drugs:- Additive effect. It improves desirable properties of the drug.
- Synergism or potentiation. Use of two or more agents that produce a pharmacological response greater than what would be expected by individual effects of each.
- Interference. It inhibits the performance of the drug.
- Displacement. It replaces the action of the drug.
- Antidote
- Non-absorbable compounds
- Enzyme inducer
- Increased excretion
Age
The effects of drugs are more pronounced in young children and elderly people. The drug action depends largely on age and developmental stage.
When pregnant, many drugs when absorbed cross the placenta and adversely affect the fetus.
Newborns generally handles drugs less efficiently than the older children or adult.
Older children metabolizes drug rapidly and handles drugs similarly to healthy adults.
Elderly adults have physiologic changes that may alter all pharmacokinetic processes. All their physiologic changes may slow excretion and promote accumulation of drugs in the body.
Body Weight
People greater than the average weight need a larger dose, provided that renal, hepatic, and cardiovascular functions are adequate and normal.
Sex
The influence is more pronounced during pregnancy and breast feeding.
Pathologic Conditions
The disease processes are capable of altering pharmacokinetic processes.
Psychologic Considerations
Influences individual response to drug administration. An example of this is the placebo effect or response, where the client is given an inert or sugar pill and is told that it would improve his condition. The client believes it and sometimes causes a therapeutic effect thus showing signs of improving health.
