An 80-year-old man with Parkinson’s disease has been...

An 80-year-old man with Parkinson’s disease has been admitted to the surgical ward for an elective bowel operation. His Parkinson’s disease is usually well controlled with co-careldopa 25/100 (carbidopa 25 mg, levodopa 100 mg) four times daily, entacapone 200 mg four times daily and co-careldopa modified release 50/200 (carbidopa 50 mg, levodopa 200 mg) at night. The surgical team plan to convert all of his medication to a dispersible formulation of levodopa and administer it via a nasogastric tube peri-operatively. What is the equivalent dose of dispersible levodopa that should be given over a 24-hour period? A. 420 mg B. 600 mg C. 660 mg D. 780 mg E. 910 mg

An 80-year-old man with Parkinson’s disease has been admitted to the surgical ward for an elective bowel operation. His Parkinson’s disease is usually well controlled with co-careldopa 25/100 (carbidopa 25 mg, levodopa 100 mg) four times daily, entacapone 200 mg four times daily and co-careldopa modified release 50/200 (carbidopa 50 mg, levodopa 200 mg) at night. The surgical team plan to convert
all of his medication to a dispersible formulation of levodopa and administer it via a nasogastric tube peri-operatively. What is the equivalent dose of dispersible levodopa that should be given over a 24-hour period?
A. 420 mg
B. 600 mg
C. 660 mg
D. 780 mg
E. 910 mg

Key Concepts

Levodopa Equivalent Daily Dose (LEDD)

LEDD is a calculated total that helps clinicians compare and convert different Parkinson’s disease medications to a common scale based on the effects of levodopa. It accounts for the various formulations and adjuvants, allowing for adjustment of medication regimens when switching formulations or planning perioperative management. This calculation is crucial to ensure the patient continues to receive an effective and equivalent dose during changes in the administration route or medication type.

Conversion Factors for COMT Inhibitors

COMT inhibitors, such as entacapone, inhibit the breakdown of levodopa, thereby increasing its bioavailability. When calculating LEDD, the presence of a COMT inhibitor is taken into account by applying a multiplier to the levodopa dose to reflect the enhanced effect. This conversion ensures that the actual clinical potency of levodopa is accurately represented in the equivalent dose calculation.

Immediate-Release Versus Modified-Release Formulations

Different formulations of levodopa, such as immediate-release and modified-release, have distinct pharmacokinetic profiles. Immediate-release formulations are absorbed quickly and their effects are generally immediate, while modified-release formulations provide a slower, prolonged release of the drug. When converting doses, different weightings or conversion factors may be applied to these formulations to accurately reflect their clinical impact in the overall levodopa equivalent daily dose.

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