ADVERSE DRUG REACTIONS
DR T R RAMANUJAM M.D., C.MI.Biol (Lond)
INTRODUCTION
DEFINITION OF A.D.R AND DRUG INTERACTIONS
CLASSIFICATION OF ADVERSE DRUG REACTIONS
ADR DUE TO DRUG INTERACTIONS
CRITERIA FOR DRUG REACTIONS
ADR DUE TO DRUG INTERACTIONS
Drugs can interfere with immunization procedures: 6MP, Methotrexate and steroids are dangerous after small pox vaccination. Chloramphenicol with tentanus vaccine – interference with immunity. Oral contraceptives interferes with tuberculin testing.
| Diagnostic test | Drug involved |
| Positive coomb’s test | Cephalothin, Rifampin |
| Increased 17 | Penicillins |
| Ketosteroids | Aldomet |
| Increased SGOT | Diaoxide |
| Increased Uric acid | Thiazides |
| Increased blood | Furosemide |
| glucose | D thyroxine, Caffeine |
| Seruk Alk | Salicylates, Clofibrate |
| Phosphatases | Erythrocin, Dilantin, |
| Allopnrinol |
Physical incompatibility–sodium phenobarb ´ Codeine PO4
Pen G Pt Vitamin C Penicillins x aminoglycosides
Pharmacokinetic drug interaction:
Hinderance with intestinal absorption:
Antacids ´ tetracycline
Digoxin ´ Resins
Azole antifungals ´ Antiacids, H2 blockers
Oral anticoagulants and lateration of bacterial flors
Interference with binding & storage:
Sulfas ´ Phenylbutazone – diaplacement from binding leading to toxicity
Warfarin ´ salicylates
Drug interaction at receptor sites:
Nasal decongestants ´ anti HT
Dopamine ´ Caffeine – antagonism
Imipramine ´ catecholamine – enhanced activity
Drug interaction with biotransformation:
MAO I ´ tricyclics – potentiation
Barbiturate ´ dilantin – reduced dilantin effect
Barbiturate ´ Warfarin – reduced warfarin effect
Drug interaction with Excretion:
Alkalisation increases aminoglycoside excretion
Probenecid ´ penicillin haiazides reduce plasma K and increase plasma Ca and Increase the toxicity of digoxin.
Important determinants of ADR:
1. The administrated drug:
Physicochemical and pharmacokinetic characteristics
Formulation characteristic
Dose of drug administered
Frequency & route of administration
2. Patient and his conditions:
Age, Sex pregnancy and nutrition (Physiological)
Associated diseases and inter current illness (Pathological)
Allergic states
Genetic predisposition
3. Additional extrinsic factors:
Other drugs administered concurrently
Alcohol / tobacco consumption
Environmental pollutants.
