Objective: To review guidelines for initiating Carbidopa/Levodopa Enteral Suspension method of delivery in the treatment of Parkinson’s Disease (PD) and to compare guidelines with real world dosing regimens following conversion.

Background: PD is a progressive neurodegenerative disorder requiring vigilance in maintaining optimum medication dosing to control PD related symptoms. Carbidopa/Levodopa Enteral Suspension method of delivery (CLES) was approved by the FDA for treatment of PD in the US in 2015. CLES guidelines recommend converting patients to instant release (IR) carbidopa/levodopa (C/L) prior to conversion to CLES. Conversion from extended release (ER) C/L to IR C/L prior to transition to CLES is often impractical.

Methods: We review 17 cases, grouped into 4 categories: those taking IR C/L, IR C/L and entacapone (ENT), ER C/L and ENT, or IR/ER C/L +/- ENT in the setting of DBS. One case was excluded due to an unknown pre-conversion PO C/L dose. One case was excluded as the patient was receiving both IR and ER C/L. Cases were selected based on diagnosis of PD, levodopa-responsive symptoms treated with oral levodopa, and conversion to CLES therapy – whereupon pre- and post-conversion daily levodopa doses were compared.

Results: In 15 cases, PD diagnosis was made by a neurologist. Total daily doses of levodopa were calculated based on scheduled doses and prn doses (average as reported by the patient). Post-conversion CLES doses were calculated as the morning dose in addition to daily rate multiplied by the number of hours the CLES pump was in use, following the initial 3 day titration period. In patients receiving IR C/L, we found a conversion ratio (CR) of 0.76 with a standard deviation (SD) of 0.27. In those receiving IR C/L and entacapone, we found a CR (SD) of 0.82 (0.25). In those receiving ER C/L and entacapone, we found a CR (SD) of 1.7 (0.86). And in those receiving IR or ER C/L in the setting of DBS, we found a CR (SD) of 1.34 (1.03).

Conclusions: The IR C/L to CLES CR has limited real world application. Our data suggest that in actuality there are different ratios depending on the C/L formulation and that C/L IR is not a 1:1 conversion. Patients suffering from increasing off times and troubling dyskinesias are often treated with ER C/L, ENT, or DBS. It follows that patients considered for CLES have already found IR C/L insufficient, conversion back to IR C/L would be demanding in the best of cases, and impossible in the worst. This study emphasizes the importance of further exploring real world dosing regimens including IR/ER C/L in the setting of ENT and DBS.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/on-converting-patients-from-oral-dopamine-agonists-to-the-carbidopa-levodopa-enteral-suspension-method-real-world-conversion-ratios/