Pharmacotherapeutics and drug interactions

Pharmacotherapeutics

it  is the use of drugs to treat disease.

types of drug therapies:-

• acute therapy, if the patient is critically ill and requires acute intensive therapy
• empiric therapy, based on practical experience rather than on pure scientific data
• maintenance therapy, for patients with chronic conditions that don’t resolve

• replacement therapy, to substitute for missing substances in the body
• supportive therapy, which doesn’t treat the cause of the disease but maintains other threatened body systems until the patient’s condition resolves
• palliative therapy, used for end-stage or terminal diseases to make the patient as comfortable as possible.
   
  -there are many Factors affecting a patient’s response to a drug Because no two people are alike physiologically or psychologically, such as
  ( age - gender - disease - drug interactions - infections -hepatic, renal and GIT functions - diet)
   
   drug dependence :-
    patient displays a physical or psychological need for the drug.
   Physical dependence produces withdrawal symptoms when the drug is stopped
  psychological dependence is based on a desire to continue taking the drug to relieve tension and avoid discomfort
  drug tolerance :-
    patient develops a decreased response to a drug over time. The patient then requires larger doses to produce the same response.
   

  Drug interactions

  Drug interactions can occur between drugs or between drugs and foods.The more drugs a patient receives, the greater the chances that a drug interaction will occur.

  1- additive action

   occur when two drugs with similar actions are administered to a patient .The effects are equivalent to the sum of the 2 drugs .

   advantages: lower doses of each drug, decreased probability of adverse reactions, and greater pain control than from one drug given alone 

   

   2- potentiation action
  also called synergistic effect occurs when two drugs that produce the same effect are given together and one drug enhances the effect of the other drug. This produces greater effects than when each drug is taken alone.

   

  3- antagonistic effect 
   occurs when the combined response of two drugs is less than the response produced by either drug alone.
   
  4- decreased or increased absorption
   two drugs are taken together can change the absorption of one or both of the drugs
  -  drugs can interact and form an insoluble compound that can’t be absorbed.
  -drugs that change the acidity of the stomach can affect the ability of another drug to dissolve in the stomach.
  it  can be avoided by administering the drugs at least 2 hours apart. 
  
  
   5-decreased or increased metabolism and excretion.
   When two drugs are given together, they can compete for protein-binding sites, leading to an increase in the effects of one drug as that drug is displaced from the protein and becomes a free, unbound drug.
   Toxic drug levels can occur when a drug’s metabolism and excretion are inhibited by another drug.