ONE OF THE FIRST DUTIES OF THE PHYSICIAN IS TO EDUCATE THE MASSES NOT TO TAKE MEDICINE….!
PRINCIPLES OFPRESCRIBING Dr. V.SATHYANARAYANAN M.D PROFESSOR OF PHARMACOLOGY SRM MCH & RC
PRINCIPLES OF PRESCRIBING AT ANY TIME 40-50% OF ADULTS TAKE PRESCRIBED MEDICINE. PRESCRIPTION IS THE FINAL DECIDING THING FOR THE ILLNESS PATIENT INCREASE IN NUMBER OF NEW DRUGS. COMPLEX DISEASE PATTERN. POLYPHARMACY.
IMPACT OF IRRATIONAL PRESCRIBING Delay in cure More adverse effects Prolonged hospitalisation Emergence of antimicrobial resistance Loss of patient’s confidence in the doctor Loss to the patient/community Lowering of health standards
THE BENEFIT:RISK RATIO IN PRESCRIBING Benefits to the patient is accompanied by the risk of Adverse effects Always try to assess the likely Benefit : risk ratio before instituting therapy.
ASSESSING RISK:BENEFIT RATIO Consider five factors:1) The seriousness of the Problem to be treated1) The efficacy of the drug you intend to use.2) The seriousness & frequency of possible ADR3) The safety of other drugs that might be used instead4) The efficacy of other drugs that might be used instead
SOME EXAMPLES Choice of an antibiotic in UTI in a 2 month pregnant woman.
Elderly lady with giant cell arteritis treated withprednislone
Treating male elderly patient with Anginapectoris for impotence
EVIDENCE-BASED MEDICINE Search and evaluate the literature for efficacy, safety Appropriateness of the particular therapeutic measure
Clinical decisions should be based on thebest scientific evidence available at the time.
EVIDENCE-BASED MEDICINEThis can be obtained from: Standard text books Review articles from leading journals Other doctors (lectures, CME etc.) Systematic review of clinical trials (published and unpublished) Websites and Database
EVIDENCE-BASED MEDICINE Therapeutic decisions should be rationally guided by Rigorous analysis of the best available evidence. Unbiased analysis.
HOW TO CHOOSE A DRUG ? Ask the following sequence of questions before writing the prescription Indicated?!! Which drug? Which class---which group----which particular drug Which route? Which formulation? What dosage regimen? With experience, the process becomes automatic
HOW TO CHOOSE A DRUG ?ASK THE FOLLOWING QUESTIONS BEFORE WRITING THE PRESCRIPTION1)Is drug therapy indicated ? A) Is the intending treatment necessary? B) Is the benefit greater than the risk?Ex) Vitamins & minerals as tonics in the absence of any evidence of deficiency antibiotics in acute diarrheas cerebral vasodilators in senile dementia
WHICH DRUG ? If drug therapy is indicated, select the therapeutic class Select the group within the class Select the particular drug in the groupEx) infection antibiotic (therapeutic class) penicillins (therapeutic group) amoxicillin (particular drug). CHF, hypertension selection complicated
HOW TO MAKE A RATIONALCHOICE? Choose the drugs which you are most familiar.Consider following factors: Pharmacokinetic (Absorption, distribution, metabolism, excretion) Pharmacodynamic ( potency-sulfonylureas in DM ) Therapeutic considerations.( disease features, severity, co-existing diseases, avoidance of ADR, Adverse drug Interactions) Patient compliance
WHICH ROUTE OFADMINISTRATION? DICTATED BY THE DRUG CHOSEN. (Ex. Dopamine) Sometimes particular route is preferred for particular benefit. (Ex. Nitrates in angina pectoris) Rectal route diazepam in children I.M depot inj. In schizophrenia to ensure compliance. S.C insulin for prolonged effect. I.V Furosemide in CHF
WHAT DOSAGE REGIMEN? IT HAS THREE ASPECTS:1) The dose of the drug.2) The frequency of it’s administration.3) The timing
PRINCIPLES THAT GOVERNDOSAGE REGIMEN: BE FLEXIBLE Pharmacokinetic variability-(absorption, metabolism, elimination) increase Or decrease Dose Pharmacodynamic variability- DRC varies between individuals, no response in initial dose increase the dose without ADR Patient factors- age, body wt, hepatic and renal function. Disease factors- degree of the disease (ex- NSAIDS in inflammation)
TAILORING THE DOSAGE REGIMEN : BE SYSTEMATIC Look up in a reliable source. Consider dose related toxicity of the drug (ex- more for lithium , gentamicin, digoxin, phenytoin) Decide on the initial dosage.( generally start at the lower end, increase it gradually), be flexible Consider pharmacokinetic factors that alter dosage ( renal insufficiency) Consider DRC (ex- insulin required more in diabetic ketoacidosis) Consider drug interactions Other factors like Age, weight
HOW FREQUENTLY TO ADMINISTER? Usually fixed of a given drug in a given formulation Sometimes need to be altered according to the frequency of symptoms (ex- GTN in angina) To prevent ADR ex-corticosteroids on alternate days To improve compliance –(MR preparations)
TIMING OF DRUG ADMINISTRATION In most cases - Fixed. To minimize the ADR- last thing at night Timing may be important in some cases ( ex- diuretics, sedatives, corticosteroids) Timing of symptoms ( ex- antacids, NSAIDS, GTN) Timing in relation to the meals (ex-most penicillins, tetracyclines, azithromycin best before food, NSAIDs like aspirin with food)
FOR HOW LONG ? It depends on nature of the disease, symptoms & collective experience. The scale varies from single dose of aspirin for headache to life long treatment for diabetes, hypertension. Difficulty & controversy arise in treatment of intermediate duration
FOR HOW LONG SHOULD TREATMENT LAST? Antibiotics duration varies from infection to infection It depends on infecting organism, site of infection, response to treatment( ex- penicillin for tonsillitis- 7-10 days, NGU - 10- 21 days, tuberculosis 6-12 months) Warfarin in DFT- duration uncertain
GOOD PRESCRIBING IS TOGIVE: RIGHT DRUG IN THE RIGHT DOSAGE RIGHT FORMULATION AT THE RIGHT FREQUENCY FOR THE RIGHT DURATION
PROCESS OF RATIONALPRESCRIBING Establish a diagnosis Define therapeutic problem and goal Select the right drug by good prescribing Provide proper information Monitor compliance Monitor goal Modify if needed Monitor ADR if occur & modify
INSTRUCTIONS TO THEPATIENT Effects of the drug Side effects Why, How and when instructions Precautions/ warnings
The good physician treats the disease;The great physician treats the patientwho has the disease ! WILLIAM OSLER