Parkinson Society BC (PSBC) recently conducted a survey with the intent of better understanding the patient’s perspective in achieving symptom control with brand name (Sinemet) vs. generic forms of levodopa.

The following is a summary of the 521 responses received:

• The most commonly used form of levodopa overall is the generic Apo-Levocarb controlled release (CR) & immediate release (IR).
• 55% of current generic levodopa users have never tried Sinemet; of those who had tried Sinemet, 42% said that their symptom control on Sinemet was the same with generic.
• 46% of current generic levodopa users expressed that they were using a generic due to the recent worldwide shortage of certain brand name formulations.
• For respondents currently taking Sinemet, 43% said that the worldwide shortage had affected them a great deal. Over 80% of Sinemet users expressed that they had tried a form of generic levodopa, with 76% reporting they were never able to achieve equivalent or better symptom control with a generic.

Overall, the results of the survey largely indicated that, in most cases, optimal symptom control was achieved with the form of levodopa that the patient was most used to. Although Sinemet and generic forms of levodopa have the same medicinal ingredients, variances in experiences led to some concern over the non-medicinal ingredients in generics.

As Apotex was the most commonly used generic form of levodopa in BC, PSBC worked to identify with BC PharmaCare its non-medicinal ingredients in the event something may be interfering with the generic’s efficacy.

BC PharmaCare noted the non-medical ingredients in Apotex CR as: hydroxypropyl methylcellulose, yellow ferric oxide (200 mg/50 mg only), red ferric oxide, purified water, and magnesium stearate.

Briefly, each non-medicinal ingredient can be summarized as:

• Hydroxypropyl methylcellulose: a thickening or coating agent, also used as a rate-controlling polymer in controlled or sustained release forms of drugs
• Yellow ferric oxide (200 mg/50 mg only): yellow pigment used in the coating of pills
• Red ferric oxide: colouring agent
• Purified water: nothing found
• Magnesium stearate: common ingredient that is often part of a pill coating; a salt made of stearic acid and mineral magnesium; used to prevent pills from sticking to each other during production and maintain the consistency of capsules. There are claims that magnesium stearate slows absorption, however, studies have yielded mixed results. If magnesium stearate does slow absorption, it does not affect the overall absorption of the drug (i.e. the drug is still absorbed, but more slowly). Ingesting very large quantities, more than one would normally consume, could potentially cause a laxative effect.

The ingredients listed above are all commonly used in the pharmaceutical industry. There does not seem to be any non-medicinal ingredients that would negatively impact the effectiveness of a generic.

In our survey, a high percentage of Sinemet users reported that their symptom control was poorer on a generic. Although there does not appear to be any concerns with non-medicinal ingredients, other possible explanations for perceived efficacy could be attributed to stress and disease progression.

Of those currently using Sinemet, a high percentage expressed that they were concerned about the worldwide shortage of the drug. It should be noted that this concern could possibly lead to stress, and stress can have an impact on overall symptom control. Additionally, as Parkinson’s is a progressive disease, it is difficult to assess the effectiveness of being switched to a generic, as changes could be attributed to disease progression.

At this time, PSBC has not identified any reasons as to why a generic is not as effective as Sinemet for some patients. We welcome any other ideas we may be able to pursue.