by : Eman El-Khateeb

Administrator in clinical pharmacy Dep.

Tanta University

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Significance???

1- polytherapy

2- pharmaceutical industry

3- Dosage regimen

4-beneficial ????

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Types of drug interaction

Drug Disease

food

pollutant

packaging

Pharmaceutical incompatibility

Drug

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Drug-Drug interaction

Definition: The interaction that

Modifies the effect of one drug (object drug) by prior or concomitant administration of another drug (precipitant drug).

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Precipitant drug: The drug that causes the altered effect

of the object drug

Object drug: The drug that its action is altered by the

precipitant drug

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Quizz 2min

• Antihypertensive drug+ salt • Hypnotic + Caffeine • Tetracycline + Calcium

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Uni-linear drug interaction

Bi-linear drug interaction

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Discuss a drug interaction

1. Indication of both drugs 2. Mechanism (HOW?) 3. Results/ outcome 4. Evaluation 5. Management & recommendation

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Mechanisms of drug interaction

Pharmacodynamic (PD)

•Affects drug action directly

Pharmacokinetic (PK)

•Affects plasma conc. with time (ADME)

Retrospective VS prospective

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First: Pharmacodymamic

interactions

PD

Addition

Effect Toxicity

Antagonism

Effect Toxicity

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Examples

• Additive: 1- Warfarin+ Aspirin(75 mg daily) Additive anticoagulant effect (Effect) 2- Atropin+ T.C.A. Additive anticholinergic side effect

(Toxicity)

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Examples (cont.)

• Antagonism 1- CNS depressant+ CNS stimulant (Effect) 2- Gallamine + neostigmine NMRB (Ms relaxant) AchEIs(Ms contraction) (Effect)

3- Digoxin + potassium (K+) (Antagonizes digoxin toxicity)

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Group excercise

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Group exercise

Illustrate the mechanism of drug interaction if present.

A- isoprotrenol + propranolol B- Benzodiazepine+ Antihistamine C- Alcohol+ barbiturates D- Aminoglycosides+ cephalosporines E- Gentamycine+ Ethacrynic acid F- Warfarine + vitamine K

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A- B- C- D- E- F-

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