click below
click below
Normal Size Small Size show me how
Drugs for PD
Drugs for Parkinson's Disease
Question | Answer |
---|---|
Parkinson's disease: signs and symptoms | Tremors at rest, rigidity, postural instability, bradykinesia |
Levodopa: minimizing gradual loss | 1. Shortening dosing interval 2. Give drug that prolong levodopa's plasma half life (like entacapone) 3. Give direct acting dopamine agonist |
Levodopa: minimizing abrupt loss of effects | Entacapone and Rasagiline |
Levodopa: mechanism of action | Increases synthesis of dopamine in striatum (enters brain where it is converted to dopamine in active form by decarboxylase) |
Levodopa: adverse effect (major one) | Dyskinesia |
Levodopa: adverse effects | Postural hypotension, psychosis, N/V, darken urine and sweat |
Levodopa: adverse effects (CV) | Dysrhythmia in patients with heart disease |
Levodopa: minimizing psychosis effects | 1. Reduce levodopa dosage 2. Clozapine and quetiapine (second generation antipsychotics, does not block dopamine) |
Levodopa: drug interactions that decreases effects of levodopa | First generation antipsychotics (chlorpromazine, halperidol) from dopamine blockade |
Levodopa: drug interactions with MAO inhibitors | Causes hypertensive crisis |
Levodopa: contraindications | Nonselective MAO inhibitors (must be withdrawn at least 2 weeks prior) |
Levodopa: drug interactions that increase effects of levodopa | Anticholinergic drugs |
Levodopa: drug interactions with pyridoxine (vitamin B6) | Stimulates decarboxylation of levodopa, which reduces its effects |
Levodopa: food interactions | High protein meals reduces therapeutic effects |
Levodopa/Carbidopa: mechanism of action | Used to enhance effects of levodopa. Inhibits decarboxylation of levodopa |
Dopamine agonists:nonergot derivatives | Pramipexole, ropinirole, apomorphine. More selective for dopamine receptors. Causes less side effects and are preferred |
Dopamine agonists: ergot derivatives | Bromocriptine and carbergoline. Less selective for dopamine receptors. Causes more side effects |
Dopamine agonists: advantages | Not dependent on enzymatic conversions to become active. Does not compete with protein for uptake and blood brain transport. Lower incidence of response failure. Less likely to cause disabling dyskinesia |
Dopamine agonists: disavantages | More serious side effects -- especially hallucinations, daytime sleepiness, postural hypotension. Should be reserved for younger patients |
Pramipexole: mechanism of action | Nonergot dopamine agonist. Binds selectively to D2 and D3 receptors |
Pramipexole: uses | Used alone in early stage PD and combined with levodopa in advanced stage PD. Also approved for moderate to severe restless leg syndrome |
Pramipexole: adverse effects (unique) | Sleep attacks and impulse control disorder |
Pramipexole: adverse effects (used alone) | Nausea, dizziness, daytime somnolence, insomnia |
Pramipexole: adverse effects (combined with levodopa) | Orthostatic hypotension, dyskinesia, hallucination |
Pramipexole: drug interactions that increases pramipexole levels | Cimetidine (drug for peptic ulcer) inhibits excretion of pramipexole |
Entacapone: mechanism of action | COMT inhibitor, prolonging half life of levodopa and decreases production of levodopa metabolites that competes with levodopa for blood brain transport |
Entacapone: adverse effects (used alone) | Yellow-orange urine, vomiting, diarrhea, constipation |
Entacapone: adverse effects (combined with levodopa) | Dyskinesia, orthostatic hypotension, hallucination, impulse control disorder, sleep disturbances, nausea |
Entacapone: drug interactions | Increases levels of drugs that are metabolized by COMT. Includes levodopa, methyldopa, dobutamine, isoproternol |
Selegiline: mechanism of action | MAO-B inhibitor, prolongs effects of levodopa and may delay progression of PD |
Selegiline: pharmacokinetics | Two metabolites that can cause harmful effects |
Selegiline: adverse effects | Insomnia |
Selegiline: adverse effects (high doses) | Inhibits MAO-A inhibitors, increasing risk for hypertensive crisis |
Selegiline: drug interactions (combined with levodopa) | Intensifies adverse effects of levodopa (orthostatic hypotension, dyskinesia, hallucinations) |
Selegiline: drug interaction | Meripidine cauases stupor, rigidity. Fluoxetine is fatal |