Levodopa

INTRODUCTION

Indications

Parkinson's disease. Not useful for drug-induced extrapyramidal reactions.

Action

Levodopa is converted to dopamine in the CNS, where it serves as a neurotransmitter. Carbidopa, a decarboxylase inhibitor, prevents peripheral destruction of levodopa. Therapeutic Effects: Relief of tremor and rigidity in Parkinson's syndrome.

Adverse Reactions/Side Effects

CNS: involuntary movements, anxiety, dizziness, hallucinations, memory loss, psychiatric problems. EENT: blurred vision, mydriasis. GI: nausea, vomiting, anorexia, dry mouth, hepatotoxicity. Derm: melanoma. Hemat: hemolytic anemia, leukopenia. Misc: darkening of urine or sweat.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Assess patient's gait and motor function to help determine antiparkinson effects, especially when starting drug therapy, or during dosing changes or addition of other antiparkinson drugs. Motor function should be assessed at different times of the day, such as when drugs are reaching peak therapeutic levels (i.e., 30–60 min after oral dose), as well as when drug effects are minimal (just before the next dose).

• Document increased side effects such as involuntary movements (dyskinesias) or fluctuations in response (on-off phenomenon, end-of-dose akinesia). Notify physician because increased side effects might require dose adjustment or a change in medication regimen.

• Monitor anxiety, hallucinations, memory deficits, and other psychologic problems. Repeated or excessive symptoms may require change in dose or medication.

• Assess dizziness and drowsiness that might affect gait, balance, and other functional activities (See Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

• Monitor signs of blood dyscrasias, including leukopenia (fever, sore throat, signs of infection) and hemolytic anemia (unusual weakness and fatigue, dizziness, jaundice, pallor, abdominal pain). Report these signs to the physician.

• Assess any skin changes because levodopa can activate malignant melanoma.

Interventions

• Implement therapeutic exercises (coordination exercises, gait training, cardiovascular conditioning) to complement the effects of drug therapy and help achieve optimal function.

• Guard against falls and trauma (hip fractures, head injury, and so forth). Implement fall- prevention strategies (See Appendix E), especially if patient exhibits Parkinson's symptoms (postural instability, rigidity) combined with drug side effects (dizziness, blurred vision, dyskinesias).

Patient/Client-Related Instruction

• Inform patient that beneficial drug effects may occur within 2–3 wk, but may also take up to 6 mo to reach full therapeutic effect. Therapeutic effects may also begin to diminish after several years of continuous use.

• Advise patient to avoid large amounts of protein in a single meal (i.e., space out daily protein intake over several meals). Levodopa is typically administered with food to reduce stomach irritation, ...