PHARMACOLOGY

FACTORS AFFECTING ACTION OF DRUGS ::

Physiological State of Mind ::

The mind affects the effectiveness of a drug either way Females are more receptive to drugs i.e. drugs act better on them faith inspired by the doctor in the mind of the patient is an important factor in medication Even in low doses cerebral stimulants are more effective in mentally depressed persons than what they are in others because they are indicated in the depressed 

pathological Disease ::

One can tolerate higher doses in diseased condition than in health During fever one can tolerate high doses of antipyretics than in a non-febrile condition Drugs act more effectively in diseased condition Iron is better absorbed during anaemia 

Biological Variation ::

Biological Variation can be defined as the appearance of differences in the magnitude of response among individuals in the same population given the same dose of drug Drug effects are never identical in all patients or even in a given patient on different occasions even if all the sources of variation are controlled 

        True as a species man is reasonably homogeneous but differences among people do exist considering responsiveness to drugs Genetic and diseased conditions are the sources of variation in drug response Usual dosage regime may need modification in patients with renal function impairment liver disorders CCF thyroid disorders g.i. diseases etc In many diseases a change in response is primarily due to a change in the pharmacokinetics of a drug 

Variations amongst species can also be seen for many drugs for example morphine acts as a depressant in all species except cats and mice where it produces excitation Pethidine is ineffective in dogs Histamine relaxes rat uterus but contracts that of other species Guinea pigs and human beings are very much susceptible to histamine -induced hypersensitivity reactions whereas others are not sensitive Histamine produces rise in blood pressure in rabbits but in others in produces fall in blood pressure