Psychiatric Drugs and Medications Q 30
The client asks the nurse why he is taking bromocriptine (Parlodel). The nurse’s reply is based in the understanding that bromocriptine mimics the effects of dopamine by:
A. Decreasing dopamine levels in the brain.
B. Decreasing the storage of dopamine peripherally.
C. Activating dopamine receptors in the brain.
D. Inhibiting monoamine oxidase type B.
Correct Answer: C. Activating dopamine receptors in the brain
Bromocriptine is a dopaminergic agent, and this response refers to its action. It is an ergot alkaloid derivative in the dopamine D2 agonist class of drugs. Bromocriptine is a dopamine receptor agonist that has selective agonist activity on D2 dopamine receptors while simultaneously acting as a partial antagonist for D1 dopamine receptors. Dopamine agonism has variable effects depending on the target tissue.
Option A: This refers to the action of levodopa. Unlike dopamine, levodopa can cross the blood-brain-barrier (BBB). Levodopa converts to dopamine in both the CNS and periphery. Levodopa is the precursor to dopamine. Most commonly, clinicians use levodopa as a dopamine replacement agent for the treatment of Parkinson’s disease. It is most effectively used to control bradykinetic symptoms that are apparent in Parkinson’s disease and it is the most effective medication to improve the quality of life in patients with idiopathic PD.
Option B: This refers to the action of carbidopa and levodopa. Dopamine decarboxylase inhibitors prevent the conversion of levodopa to dopamine in the periphery, allowing for more levodopa to cross the BBB. Once converted to dopamine, it activates postsynaptic dopaminergic receptors and compensates for the decrease in endogenous dopamine. Carbidopa is added to levodopa formulations to decrease the peripheral conversion of L-dopa to dopamine to reduce gastrointestinal side effects and increase levodopa bioavailability in the central nervous system (CNS).
Option D: This refers to the action of selegiline. Selegiline is an irreversible inhibitor of monoamine oxidase (MAO), an enzyme that catabolizes norepinephrine, serotonin, and dopamine. The blockage of this enzyme prevents the reuptake of these neurotransmitters in the CNS, conferring increased levels of the biologically active monoamines at the synaptic cleft. With lower doses, selegiline exhibits selective B-type monoamine oxidase (MAO-B) inhibition.