The plant or extract can then be evaluated by various biological methods to determine pharmacological activity, potency, and toxicity. The biological evaluation would serve better than the physical and chemical evaluation for drugs that could not be satisfactorily assayed by these last two methods.
BIOLOGICAL EVALUATION
The plant or extract can then be evaluated by various
biological methods to determine pharmacological activity, potency, and
toxicity. The biological evaluation would serve better than the physical and
chemical evaluation for drugs that could not be satisfactorily assayed by these
last two methods. Moreover, this is an important method, the crude drugs are
considered important only because of their biological effects and this
evaluation would conclude the effect. These methods are considered to be less
precise, more time-consuming and more expensive. Bioassays should be as simple
as possible, and attempts should be made to have access to a large number of
different tests so that many biological properties can be screened. The
bioassay methods are of three types they are, toxic, symptomatic and tissue or
organ methods. Different animals are used in toxic and symptomatic method and
isolated organ or tissue is used in the third method.
These assays are conducted by determining the amount of drug
of known potency required to produce a definite effect on suitable test animals
or organs under standard conditions. Reference standard are used in certain
bioassay procedures to minimize errors.
Toxicity studies are performed in suitable animal models to
decide the lethal dose and effective dose of crude drags. Mice are used to test
the effects of various vaccines.
Oxytocic activity of vasopressin injection is tested on
guinea pigs, and oxytocic injection is assayed on young domestic chickens by
injecting into an exposed crural or brachial vein and noticing the changes in
blood pressure. Pigeons are used to assay Digitalis glycosides by transfusing
the drug through the alar vein to the blood stream and observing the lethal
effects. Depressor activities and mydriatic effects of certain drugs are tested
in cats and cat’s eye, respectively. Anthelmintic drugs are evaluated on worms.
The drugs that have an effect in eyes are assayed on
rabbit’s eyes. Dogs are used to assay the drugs that exhibit cardiac and
gastrointestinal activities. Effects of Ergot are carried out on cock’s comb or
rabbit’s intestine or its uterus. Next to the animals, the studies are carried
out in human beings also. In some instances, the effects that are observed from
animal studies would be different when tested in humans. The tested biological
activities include hepatoprotective activity, hypoglycaemic activity,
antiinflammatory activity, antiulcer activity, immunomodulatory activity, etc.
Microbiological assays are carried out to determine the
effects of drug in various microorganisms, and this is employed in the
identification of antimicrobial drugs. The methods used in this type of assays
are agar well-diffusion method, disc-diffusion method, and turbidimetric
method. In other microbiological methods, the living bacteria yeast moulds are
used for assaying vitamins.
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