Aclient whose parkinson's disease is being treated with tolcapone should concurrently take what drug?

The correct answer would be levodopa/carbidopa.

Tolcapone is a drug used as an adjunct to levodopa/carbidopa combination medication.

These drugs are used to treat the symptoms of Parkinson's disease.

Tolcapone is used to inhibit enzyme COMT (catechol-O-methyl transferase).

In the brain, levodopa is converted into dopamine which helps in controlling the movement.

Carbidopa helps in preventing the breakdown of levodopa in the blood which allows more levodopa to enter the brain. In addition, it helps in reducing the side-effects associated with levodopa such as vomiting, nausea et cetera.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."