You may need several weeks or even months to notice an improvement after you start taking carbidopa-levodopa, especially if your doctor is adjusting your dose to find the optimal treatment amount. Keep in touch with your doctor and report any new or continuing symptoms. Some people may not benefit from carbidopa-levodopa. Others may find that the treatment seems to wear off between doses. Over time, carbidopa-levodopa may lose its effectiveness. Talk to your doctor if your symptoms change or worsen.