Important terms regarding Drugs in VIVA / OSPE

In medical colleges, these terms are mostly ask by Professors in VIVA or OSPE. So here are some important terms regarding drugs actions :

i) ADDITION :

 When two drugs with same effect are given together then they produce an effect that is equal in magnitude and their sum of effect will be 1+1=2. 

ii) SYNERGISM :  

Two drugs with the same effect when given together produce an effect that is greater than the sum of effects of two given individually, 1+1= >2. 

  For example = Xanax is a drug when given together with antidepressant like prothiadine then the drowsiness effects of both drugs is enhanced and multiplied. 

iii) POTENTIATION : 

: A drug lacking an effect of its own but increase the effect of second active drug, 0+1= >1. 

  For example : Beta lactamase inhibitors are given with pencillins to enhance their effect. 

iv) TOLERANCE :

 Gradual decrease in response of drug after repeated administration. Usually occurs after weeks or months. 

v) TACHYPHYLAXIS :

: Rapid decrease in responsiveness of drug after administration. May occurs in minutes or hours. 

vi) HYPOREACTIVITY :

 For a given dose , intensity of effect is diminished, in comparison to effect seen in most individuals. 

vii) HPERREACTIVITY :

 For a given dose, intensity of effect is greater, in comparison to effect seen in most individuals. 

viii) IDIOSYNCRACY : 

An unusual drug response elicited by an individual is called idiosyncracy. It is caused by;

              • Genetic difference in metabolism of drug. 

              • Allergy

ix) HYPERSENSITIVITY :

 It refers to allergic or other immunologic response to drug & involves antigen antibody reaction. 

       • It is one of the cause of IDIOSYNCRACY. 

x) PHYSIOLOGIC DRUG DEPENDENCE :

: It is a state in which deprivation of drug result in unpleasant symptoms ususally opposite to drug’s effect. 

xi) PSYCOLOGIC DRUG DEPENDENCE : 

It is a psychic state in which deprivation of drug result in severe anxiety and abstinence syndrome on other part of patient. 

       • It is usually seen in addicts who feels compelled to use drug. 

xii) POTENCY(ED/EC 50) :

 It refers to the concentration or dose of drug required to produce 50% of drug maximal effect.

                                         OR

  : It is also known as effective dose concentration and is measure of how much drug is required to elicit a response.  

        • The affinity of receptor for the drug is an important factors in determining the potency. 

xiii) EFFICACY : 

It is refer to the maximal response produced by a drug. 

       • The clinical effectiveness of the drug depend upon its efficacy not on it’s potency, so efficacy is more important than potency. 

       • Efficacy focuses on the response of the drug in the body while potency is a relative measurement of effectiveness between two drug. 

xiv) TOXIC DOSE(TD50) :

 It is the dose required to produce a particular toxic effect in 50% of the individuals. 

xv) LETHAL DOSE(LD50) : 

The dose required to cause the death in 50% of the individuals. 

xvi) THERAPEUTIC INDEX : 

It is the ratio of the dose that produce toxic effects to the dose that produce desirable clinical effects. 

                                   OR

 : It is the ration of TD50 to ED50. 

 

    • Therapeutic index = toxic dose / effective dose. 

    • Greater the therapeutic index , greater will be the safety of the drug, large dose required to cause toxicity. 

 

For example : Pencillin has large therapeutic index so it i safe. & warfarin, lithium salts have small therapeutic index so they are unsafe. 

xvii) AFFINITY OF DRUG : 

It is an ability of a drug to binds with its receptor. 

(xviii) BIODISPOSITION :

It is the the process of metabolism and excreation.