NERVOUS SYSTEM: DOPAMINERGIC DRUGS FOR PARKINSONS

Question 1

DOPAMINERGIC DRUGS FOR PARKINSONS: INDICATIONS

Answer 1

• Early Parkinson’s disease
• Later PD
• Secondary Parkisonisml

Question 2

DOPAMINERGIC DRUGS FOR PARKINSONS: MOA

Answer 2

• Def of dopamine in the NIGROSTRIATAL PATHWAY
• Via direct and indirect circuits, this causes the basal ganglia to exert greater inhibitory effects on the thalamus which, in turn, reduces excitatory input to the motor cortex.
• By contrast, levodopa (L-dopa) is a precursor of dopamine that can enter the brain via a membrane transporter. Ropinirole and pramipexol are relatively selective agonists for the D2 receptor, which predominates in the striatum

Question 3

DOPAMINERGIC DRUGS FOR PARKINSONS: ADVERSE EFFECTS

Answer 3

• Nausea
• Drowsiness
• Confusion
• Hallucinations
• Hypotension
• Wearing off effect
• Dyskinesias at the beginning of dosage interval
  ON/OFF EFFECT

Question 4

DOPAMINERGIC DRUGS FOR PARKINSONS: WARNINGS

Answer 4

• Elderly
• Those with existing cognitive or psychiatric dx due to risk of causing confusion and hallucinations
• Used cautiously in those with CVD risk

Question 5

DOPAMINERGIC DRUGS FOR PARKINSONS: IMPORTANT INTERACTIONS

Answer 5

• Levodopa is always given with a peripheral dopa-decarboxylase inhibitor (e.g. carbidopa) to reduce its conversion to dopamine outside the brain
• This desirable interaction reduces nausea and lowers the dose needed for therapeutic effect.
• Dopaminergic agents should not usually be combined with antipsychotics (particularly first-generation) or metoclopramide because their effects on dopamine receptors are contradictory.

Question 6

DOPAMINERGIC DRUGS FOR PARKINSONS: EXAMPLES

Answer 6

• levodopa (as co-careldopa, co-beneldopa)
• ropinirole
• pramipexol