Levodopa, Carbidopa

Summary

Levodopa and carbidopa are medications given in combination to treat Parkinson’s disease. Levodopa can cross the blood brain barrier to enter the brain, where it is converted into dopamine. Carbidopa on the other hand, is given along with levodopa to help more levodopa reach the brain. This drug combination is very effective in treating the symptoms of Parkinson's disease. Side effects include psychiatric disturbances and orthostatic hypotension. Levodopa and carbidopa must not be stopped suddenly, or a paralysis known as akinetic crisis can occur. Instead, the patient should taper off the drug slowly.

Key Points

• Levodopa, Carbidopa
  • Mechanism
    • Dopaminergic drug combination
    • Levodopa is converted to dopamine in the brain, and carbidopa is added to increase the amount of dopamine that reaches the brain. Without carbidopa, 99% of levodopa gets converted into dopamine before it reaches the brain and requires a really large dose to be effective, causing severe side effects. Carbidopa allows for a smaller dose of levodopa with higher effectiveness.
    • Has a short half-life and must be taken 3-4 times per day
  • Clinical Use
    • Parkinson Disease
      • Helps with bradykinesia and tremors
      • Full therapeutic effect may take up to 6 months
  • Side Effects and Adverse Reactions
    • Orthostatic hypotension
      • Expected side effect
      • Instruct patient to rise slowly
    • Akinetic crisis if stopped suddenly
      • Complete loss of movement
      • Can present if levodopa/carbidopa is stopped suddenly. The drug must be tapered off to prevent akinetic crisis.
    • Psychiatric disturbances
      • Psychosis, confusion, hallucinations, delusions, agitation
      • Carbidopa decreases peripheral side effects, but can actually worsen central side effects like anxiety or agitation
    • Agranulocytosis
      • Decreased white blood cell count
    • Dark colored urine and sweat
    • Angioedema
    • Heart palpitations
    • Nausea and vomiting