Any 2 drugs can interact together by 2 ways:
- Positively
- Addition
- Synergism
- Potentiation
- Negatively
- Antagonism
- Reversal
Addition action
Action is summation of both drugs action
1+1=2
Addition benifit
Combination side effects are less than higer dose of one of them
Drug examples with addition action:
Asprin and paracetamol are both alangesic
Synergism action:
Action of the 2 drugs is multiplied
1+1 > 2
Synergism causes:
Exagerated side effects that may lead to death
Synergism drug examples:
Ethanol and barbiturates causes SEVERE CNS depression
Potentiation action
The 2 drugs together cause slighlty higher action than the drug alone and one drug has 0 action
1+0 > 1
Potentiation drug example
Barbiturates (zeor alangesic effect) with asprin cause a higher alangesic effect than asprin alone
Reversal action
2 drugs taken together cause reversal of the action
Drug examples that cause reversal action
- Adrenaline is reversed by Prazosin (alpha-blocker)
Hypertenstion is reversed to hypotention - Acetylcholine is reversed by atropine
Hypotension is reversed to hypertension - Resperine is reversed by MAO
Hypotension is reversed to hypertension
Antagonism action and types
The drugs oppose each other's action
Can be
- Chemical
- Physiological
- PharmacologicalChemical antagonism examples:
- Neutralization: Protaminand heparin
- Cheleation: EDTA and calcium
Desferoxamine and iron
Physiological action
2 drugs acting on 2 different receptors producing 2 opposing actions
Physiological action example:
Adrenaline and histamine works on adrenergic and histaminic receptors actions oppose each other but different receptors are triggered
Pharmacological action
2 drugs working on the same receptor
Pharmacological action examples:
Antihistaminic drugs blocks histamine receptors. Decreases allergy
