Pharmacodynamic interactions

Exemplifying few pharmacodynamic interactions.

1. Pharmacodynamic interactions MASH’HOOD MAHMOOD KHAN SHAHID

2. Drug interactions Drug interaction is said to occur if effect of one drug is altered by co-administration of another drug, herbal medicine, food or other environmental chemicals. These could be clinically relevant or irrelevant. These are classified as; Pharmaceutical Pharmacokinetic Pharmacodynamic MAJOR CAUSES: POLYPHARMACY MULTIPLE PRESCRIBERS COMORBIDITIES ERROR IN TAKING DRUG NARROW THERAPEUTIC INDEX DRUGS

3. PAHRMACODYNAMIC INTERACTIONS Pharmacodynamic interactions are those in which effects of one drug are altered by the other drug at its site of action. Mechanistically , these interactions are either DIRECT or INDIRECT interactions. These interactions could be; Loss of therapeutic effect Toxicity Unexpected increase in pharmacological activity.

4. mechanisms Direct interactions Drugs with similar or opposing pharmacological actions are employed. These are categorized as; Additive/Synergism Potentiation Antagonism Indirect interactions Both of the drugs have unrelated effects, however, ultimate outcome of combination is the incidence of interaction. These interactions are of major, moderate or minor status based upon adversity.

5. EXAMPLES

6. EXAMPLES ADENOSINE THEOPHYLLINE THEOPHYLLINES MAY ANTAGONIZE THE CARDIOVASCULAR EFFECTS OF ADENOSINE.

7. EXAMPLES NSAID WARFARIN INCREASED RISK OF BLEEDING.

8. EXAMPLES VERAPAMIL BETA- ADRENERGIC ANTAGONISTS BRADYCARDIA & ASYSTOL

9. EXAMPLES CLOZAPINE CO-TRIMOXAZOL INCREASED RISK OF BONE MARROW SUPPRESSION.

10. EXAMPLES 5-FLUOROURACIL FOLINIC ACID EFFICACIOUS INHIBITION OF THYMIDYLATE SYNTHETASE; THUS MORE INHIBIOTORY AND CYTOTOXIC TO CANCEROUS CELLS.

11. EXAMPLES AMINOGLYCOSIDE FUROSEMIDE SYNERGISTIC OTOTOXICITY

12. EXAMPLES WARFARIN ASPIRIN/ FIBRATES/ THYROID HORMONE INCREASED ANTICOAGULANT EFFECT OF WARFARIN.

13. EXAMPLES ACE INHIBITOR SALICYLATES EFFECT OF ACE-INHIBITOR IS REDUCED BY; INHIBITION OF PROSTAGLANDIN SYNTHESIS

14. EXAMPLES DIGOXIN AMIODARONE/ CLARITHROMYCIN/ POTASSIUM/ QUINIDINE INCREASED INCIDENCE OF DIGOXING-TOXICITY

15. EXAMPLES K-SPARING DIURETICS POTASSIUM SUPPLEMENTS HYPERKALEMIA; IF SERIOUS MAY LEAD TO CARDIAC FAILURE AND EVEN DEATH

16. EXAMPLES ACETAMINOPHEN ALCOHOL INCREASED RISK OF ACETAMINOPHEN INDUCED LIVER DAMAGE

17. WARFARIN GARLIC/ GINGER INCREASED RISK OF BLEEDING ANTI-CONVULSANTS WORMWOOD DECREASE IN SEIZURE THRESHOLD DIGOXIN HAWTHORNE INCREASED DIGOXIN TOXICIITY

18. interventions There are many possible interventions to avoid or minimize the risk of drug interactions; Thorough review of patient history and identify patient risk factors. Be knowledgeful about the actions of drugs being used. Switch one of the potential interacting drugs. Allow a gap between administration of interacting drugs. Alter the dose of one interacting drug. Advise patient to seek guidance if they are going to plan a change in lifestyle or medications (as herbal or supplements). Education of patient and monitor history.

19. REFERENCES DRUG INTERACTION FACTS 2009 CLINICAL PHARMACY AND THERAPEUTICS (BY ROGER WALKER) BASIC AND CLINICAL PHARMACOLOGY 13 TH EDITION (BERTRAM G. KATZUNG)

20. THANKS