WHAT IS IT?
Levodopa/Carbidopa (Sinemet) is a combination medication that has two components: when given together their net effect is to INCREASE DOPAMINE IN THE CENTRAL NERVOUS SYSTEM. Let us make sure this fact does not go overlooked in the sea of details below.
Levodopa (L-dopa) is a dopamine pre-cursor that can cross the blood brain barrier. Once in the CNS it is converted by dopa decarboxylase into dopamine. As a result, it can fall under the broader category of dopaminergic medications.
Carbidopa is a medication that blocks the peripheral conversion of L-dopa (by inhibiting DOPA decarboxylase outside the CNS). When given in combination with L-dopa it will allow more of the L-dopa to be converted into dopamine in the CNS. This will also help reduce the side effects of peripheral L-dopa conversion (such as nausea and vomiting).
WHEN DO WE USE IT?
WHEN DO WE AVOID USING IT?
Extrapyramidal Effects (EPS): this medication is not effective in the management of EPS.
Concomitant use with nonspecific MAOI inhibitors: these two medications will interact together to provide for the potential for hypertension, headache, and hyperexcitability.
In patients with Angle-closure glaucoma: this medication might exhibit some cholinergic activity, which can cause the eyes to dilate. Medications that cause dilated pupils are contraindicated in angle-closure glaucoma due to the fact that they can worsen the condition.
HOW IS IT ADMINISTERED?
This medication is administered orally.
HOW IS IT DOSED?
Initial dose: 100 mg levodopa/25 mg carbidopa (single combined tablet) given 3 times a day.
Increasing dose: every day increase the number of tablets administered by 1, until the patient is on a daily dose of 800 mg levodopa/200 mg carbidopa (8 tablets).
- This is the maximum dose that needs to be reached to assess if this combined therapy is effective
- If patients experience severe side effects the maximum tolerated dose should be used (if providing symptom relief)
WHAT ARE THE SIDE EFFECTS/TOXICITY?
When in older patients this medication can cause somnolence, confusion, and hallucinations
Arrhythmia’s can be caused by peripheral conversion (outside the CNS) of this medication to dopamine
“On-off phenomenon”: given the role of dopamine in the basal ganglia, long term usage of this medication can lead to dyskinesia with akinesia between doses.
- Dyskinesia: choreiform/dystonic movements
ANYTHING ELSE TO KEEP IN MIND?
Page Updated: 08.06.2016