Dystonia treatment: Can it impair bone growth?

My 6-year-old daughter has been prescribed Madopar as a trial medication for what her neurologist suspects is dopa-responsive dystonia. I have read that this drug can impair bone growth. Can you comment on whether this is true?

- Sharon / England

Answer

Individuals with dopa-responsive dystonia improve dramatically with medications based on the amino acid levodopa (L-dopa), which the body converts into dopamine.

The medication Madopar is a combination of levodopa and benserazide. Levodopa enters the brain and increases dopamine levels. Benserazide is a drug that inhibits metabolism of levodopa in the liver, so more levodopa is able to enter the brain. Although animal studies suggest that benserazide may impair bone growth, human studies have found no such effect.

Another option for treating dopa-responsive dystonia in children is a drug called Sinemet, which is a combination of levodopa and carbidopa. Like benserazide, carbidopa also improves symptoms of dopa-responsive dystonia but appears to have no effect on bone growth. Sinemet is available in the United Kingdom.