Drugs Modifying Adrenergic Transmission
α Methyl-p-tyrosine
⭣
Inhibits tyrosine hydroxylase (The rate-limiting enzyme)
⭣
Depletes catecholamines
α Methyldopa
⭣
Inhibits dopa decarboxylase
⭣
Instead of noradrenaline, α methyl adrenaline is produced
⭣
A false transmitter
⭣
Does not stimulate receptor
Guanethidine & Bretylium
⭣
Inhibit nerve impulse coupled release of neurotransmitters
⭣
Decreased adrenergic activity
Receptor agonists e.g. phenylephrine, salbutamol etc.
⭣
Stimulate receptors
⭣ Increased adrenergic activity
Receptor antagonists e.g. phentolamine, propranolol etc.
⭣
Block receptors
⭣
Decreased adrenergic activity
Cocaine & Desipramine
⭣
Inhibit axonal uptake by NET
⭣
Noradrenaline stays in synaptic cleft
⭣
More stimulation of the receptors
⭣
Increased adrenergic activity
Reserpine
⭣
Inhibits vesicular uptake by VMAT
⭣
More noradrenaline stays in cytoplasm
⭣
Degraded by MAO
⭣
Decreased adrenergic activity
Amphetamine, Tyramine etc
⭣
Displaces noradrenaline from its storage sites
⭣
Noradrenaline moves into cytoplasm
⭣ Reverse transport & exchange diffusion
⭣
More noradrenaline in the synaptic space
⭣
Stimulation of receptors
⭣
Increased adrenergic activity
MAO inhibitors e.g. tranylcypromine
⭣
Inhibits MAO
⭣
Catecholamines are not degraded
COMT inhibitors
⭣
Inhibits COMT
⭣
Catecholamines are not degraded
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