NAPLEX Question of the Week: Dopamine Deficiency

This week's question focuses on a very important neurologic disease.
NAPLEX Question of the Week: Dopamine Deficiency

RJ is a 75-year-old male who presents to your pharmacotherapy clinic with complaints of a resting tremor in both hands and an unsteady gait. After his visit with the provider, he is diagnosed with Parkinson’s disease. The third-year medical resident has a few questions regarding some of the medications used in the treatment of Parkinson’s disease and consults the pharmacist in the clinic.

Which of the following statements is/are correct regarding the medications used in the management of Parkinson’s disease? Select all that apply.

A. Apokyn is a dopamine agonist that is available as extended-release tablets

B. Zelapar is contraindicated in patients with concomitant use of meperidine, tramadol and methadone.  

C. Reglan is an appropriate option to treat nausea and vomiting resulting from Parkinson’s disease medications

D. Cogentin is an anticholinergic agent primarily used for tremor

E. Neupro is a dopamine agonist injection used in patients with advanced Parkinson’s disease

F. Dark discoloring of urine, saliva, and sweat has been observed in patients being treated with Sinemet

Brand/Generics covered: Apokyn (apomorphine), Zelapar (selegiline), Reglan (metoclopramide), Neupro (rotigotine), and Sinemet (carbidopa/levodopa), Cogentin (benztropine)

Parkinson’s disease is neurological disorder characterized by the progressive loss of dopaminergic neurons. Primary clinical symptoms of Parkinson’s disease include bradykinesia, muscular rigidity, resting limb tremor, gait dysfunction and loss of postural reflexes. Pharmacologic treatment for Parkinson’s disease includes a number of agents: Dopamine replacement drugs and agonists such as carbidopa/levodopa (Sinemet) and ropinirole (Requip); Catechol-O-methyltransferase (COMT) inhibitors (entacopone); Selective monoamine oxidase type B (MAO-B) inhibitors (selegiline);  Centrally acting anticholinergics (benztropine); and N-methyl-D-aspartate (NMDA) receptor antagonists (amantadine).

Correct answers with rationale:

The correct answers are B, D and F

Answer choice A is incorrect. Apokyn (apomorphine) is a dopamine agonist injection used in patients with advanced Parkinson’s disease. Treatment with Apokyn must be started with a test dose in a medical office. Additionally, the concomitant use of Apokyn with 5HT3 antagonists (ondansetron) is contraindicated due to the risk of severe hypotension and loss of consciousness.  

Answer choice B is correct. Serotonergic opioids may enhance the effect of Zelapar (selegiline), a selective MAO-B inhibitor. This could result in serotonin syndrome. Clinical signs and symptoms of serotonin syndrome include behavioral and mental status changes (confusion, hallucinations), autonomic effects (syncope, sweating, fever) and somatic effects (muscular rigidity, muscle twitching). At least 14 days should elapse between discontinuation of these type B MAOIs and initiation of methadone, tramadol, or meperidine.

Answer choice C is incorrect. Reglan (metoclopramide), a dopamine receptor antagonist, worsens parkinsonian motor symptoms and should be avoided in patients with Parkinson’s disease. Additionally, Reglan has a boxed warning due to the drug’s potential to cause tardive dyskinesia.

Answer choice D is correct. Cogentin (benztropine) is a centrally acting anticholinergic agent that is primarily used for tremor. While used in the symptomatic treatment of selected patients with postural tremor, it should not be used as first-line treatment.

Answer choice E is incorrect. Neupro (rotigotine) is a dopamine agonist that is available as a transdermal patch. Neupro, applied once daily, is the only transdermal system available for the treatment of Parkinson’s disease. Selegiline is available as a patch (Emsam) but it is approved for major depressive disorder. 

Answer choice F is correct. Brown, black, or dark discoloring of urine, saliva, or sweat has been reported in patients being treated with Sinemet. Patients should be advised of this and the potential for clothing discoloration. Other adverse events associated with the use of Sinemet include hemolytic anemia (positive Coombs test), priapism and elevated uric acid levels.

Have a great week everyone!

Dr. B

NAPLEX Competencies Covered: Area 1 (Obtain, Interpret, or Assess Data, Medical or Patient Information) 1.5 signs and symptoms of medical conditions, health physiology, etiology of diseases or pathophysiology; Area 2 (Identify Drug Characteristics), 2.1 pharmacology, mechanism of action, or therapeutic class; 2.2 Commercial availability; prescription or non-prescription status; brand, generic, or biosimilar names; physical descriptions; or how supplied; Area 3 (Develop or Manage Treatment Plans), drug dosing or dosing adjustments; duration of therapy; 3.5 drug route of administration, dosage forms, or delivery systems; 3.6 drug contraindications, allergies, or precautions; 3.8 drug interactions


Sinemet Package Insert 

Zelapar Package Insert 

Apokyn Package Insert 

Neupro Package Insert 

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