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The conflict between levodopa and B6 is not at the level of absoption from the gut, but metabolism of levodopa once it is absorbed. In order to be converted to dopamine, levodopa is acted on by an enzyme called dopa decarboxylase. This enzyme uses vitamin B6 as a cofactor. This enzyme exists in great amounts outside the brain also. B6 therefore facilitates the use of levodopa OUTSIDE the brain, and makes less of it available to cross into the brain where it is needed. The purpose of carbidopa is to inhibit that enzyme outside the brain, thereby making more levodopa available to the brain where it is converted to dopamine. The carbidopa does not cross into the brain, so it has no effect on the conversion of dopa to dopamine in the brain, but by sparing levodopa outside the brain, more levodopa is able to cross into the brain where it is effective after it is converted to dopamine. B6 makes carbidopa less effective by competing with it and activating the decarboxylase enzyme. If carbidopa is less effective, then more levodopa is "wasted" outside the brain, making the medicine less effective overall. The truth is that you need fairly large quantities of B6 to overcome the effect of carbidopa. However, the usual recommendation is that people on levodopa/carbidopa should not take vitamin B6 supplementation. Jorge A Romero, MD ----- Original Message ----- From: "Kathrynne Holden, MS, RD" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, September 18, 2001 10:14 PM Subject: Re: Vitamin B Ken & Betty Rowland wrote: > > Is there some conflict between vitamin B-6 and some PD meds? > > Ken Rowland When levodopa was first used as a medication to treat Parkinson's disease, it was soon discovered that absorption of levodopa could be blocked by vitamin B6. So people using levodopa were advised to avoid vitamins containing B6 and foods containing large amounts of B6. Later, levodopa was combined with carbidopa (Sinemet, Sinemet CR) or benserazide (Madopar). The carbidopa and benserazide "protect" the levodopa, so foods containing vitamin B6 are no longer a concern. Vitamin supplements containing more than 15 mg of B6 should be taken separately from Sinemet or Madopar by at least an hour - that amount of B6 could overwhelm the protective effect, and interfere with levodopa absorption. Kathrynne Holden, MS, RD -- "Ask the Parkinson Dietitian" http://www.parkinson.org/ Author: "Eat well, stay well with Parkinson's disease" "Guidelines for Medical Nutrition Therapy for Parkinson's disease" http://www.nutritionucanlivewith.com/ ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn