Dopaminergic Drugs

DO PA M I N E R GI C D R U G S

D O P A M I NE D 2 R E C E P TO R A G O NI S T S : P R A M I P E X O L E , B R O M O C R I P T I NE

M E C H A N I S M O F A C T I O N • Acts on D2 receptors, which are Gi PCRs, when activated can induce inhibitory effects onto the target cell • Can act at the striatal neuronal cells of the striatum of the basal ganglia of the indirect pathway, in order inhibit the pathway, thus preventing turning down of movement by the basal ganglia. • Also inhibits lactotroph cell growth, reducing size of adenoma and inhibit secretion of prolactin.

I N D I C A TI O N : • Parkinson’s Disease, treatment of extrapyramidal side effects of traditional neuroleptics, treatment for hyperprolactinemia and prolactinoma

D O P A M I NE D 2 R E C E P TO R A NT A G O N I S T S ( NE U R O L E P T I C S ) : C H L O R P R O M A Z I NE , C L O Z A P I NE , R I S P E ROD O NE , E T C .

M E C H A N I S M O F A C T I O N • Acts as a blocker of D2 receptors, resulting in acute effects of increased dopamine release from dopaminergic neurons. • Therapeutic effects come from chronic use, where excessive dopamine excitation of D1 receptors result in tachyphylaxis of the receptor, resulting in the downregulation of D1 receptors, reducing firing from neurons. • Many of these drugs also have blockade effects on other receptors, resulting in other therapeutic effects (e.g., 5-HT2A block for treatment of drug induced psychosis)

I N D I C A TI ON : • Psychosis and Manic Episodes (Reduces Dopaminergic neuron firing in the long term)

S I D E E F F E C TS : • Extrapyramidal effects (Parkinson like symptoms), Hyperprolactinaemia, etc.

L E V O D O P A :

M E C H A N I S M O F A C T I O N • It is a precursor to dopamine, in order to be taken up by dopaminergic neurons in order to be converted by dopamine decarboxylase into dopamine. • Usually given with carbidopa.

I N D I C A TI O N : • Short term treatment of Parkinson’s disease (dopamine neurons degradation reduces effectiveness of drug)

D O P A MI NE D E C A R B O X Y L A S E I N H I B I T O R : C A R B I D O P A

M E C H A N I S M O F A C T I O N • An inhibitor of dopamine decarboxylase, but it is polar, thus is not a BBB penetrant. • It is used along with levodopa in order to supply the CNS dopaminergic neurons with levodopa, without any levodopa being converted to dopamine in the periphery.

I N D I C A TI O N : • Parkinson’s (along with Levodopa and other dopamine agonists)