PHARMACOLOGY

 TACHYPHYLAXIS ::

Tachyphylaxis is defined as an acute type of tolerance in other words it is quickly acquired it is reversible in nature Therefore the drug can be restarted after a good length of interval Drugs like ephedrine tyramine etc are examples These drugs act by releasing the neurotransmitter noradrenaline Tachyphylaxis occurs due to decrease in stores of transmitter 

Drug-Resistance ::

It is also a phenomenon decreased responsiveness to drugs brought about by prolonged usage of drug This is different from tolerance in that it may develop even if the patient is not exposed to that particular agent Secondly increase in dose will not produce the effect if there is drug resistance Third drug -resistance is common for chemotherapeutic agents Drug -Resistance is one -way phenomenon and it is transmitted from generation to generation of microbes in drugs like sulphas streptomycin etc Here if the drugs are administered in inadequate doses in the beginning They prove ineffective later on Even in full doses the microbes genetically keep on resisting the drug action 

Drug Interaction ::

When different drugs interact amongst themselves in the body it is called drug interaction These are more often harmful to the body To quote a few examples ::

1.During digitalisation if thiazide diuretics are given they decrease potassium in the heart and increase the toxicity of digitalis 

2.Phenylbutazone (analgesic ) displaces dicoumarin (anticoagulant ) which is bound to plasma proteins and leads to hypoprothrombinemia and hemorrhages 

        Many a times interaction of drugs in the body may have serious consequences through administered separately for independent therapeutic benefit