PHARMACOLOGY

 TYPES DRUG INTERACTIONS ::

Considering the clinical significance drug interactions may be 1.Beneficial or 2. Adverse 

Beneficial Drug Interactions ::

    Some drug interactions may be desirable and intended because of beneficial effects they produce when a combination of medications is given Such a combination produces improved therapy a greater margin of safety more appropriate onset or duration of action lowered toxicity or enhanced potency with diminishing side effects Such an interaction is also termed as rational drug interactions Table give examples of well tried combinations 

Potential advantage                                                                             example 

Improved compliance  :     Antitubercular-I agents (rifampicin and isoniazide ) I-ctrous sulfate and Folic                                                 acid 

Ease of administration :     Triple vaccine (diphtheria pertussis and tetanus ) 

Synergistic effect         :     Trimethoprim +Sulfamethoxazole Aspirin+ codeine Estrogen +progesterone                                             (oral contraceptive ) 

Decreased adverse effects :: Levodopa+Carbidopa Aluminium salt and magnesium salt (antacids) 

Adverse drug interactions ::

Usually when one talks of drug interaction it is meant adverse drug interactions It occurs due an error of the patient or physician Thus adverse- drug -interactions are undesirable and unintentional however they are not uncommon It has been estimated that interactions form about 7% of all adverse drug reactions and that among the few patients who die from adverse drug reactions (about 4% of all deaths) about one -third are due to adverse drug interactions 

        The drug interactions may be Hetergic or Homegic Hetergic type of drug -interaction occurs when two drugs producing different types of effects are administered Homergic type of drug interaction occurs when two drugs producing similar effects are administered The consequences of drug interaction or type of effect produced by drug interaction may be addition synergism or antagonism 

    Drug interaction involves one drug which precipitates the change in the effect of another The drug which precipitates the interaction is called the precipitant drug and the drug whose action is affected is called object drug