Carbidopa-Levodopa is used to treat which condition?

• A. Alzheimer disease
• B. Parkinson disease
• C. Multiple sclerosis
• D. Amyotrophic lateral sclerosis

Answer: (B)

This question tests your understanding of which condition responds to this combination therapy. Parkinson disease is characterized by a deficiency of dopamine in the brain, particularly in the basal ganglia, which leads to the hallmark motor symptoms like tremor, rigidity, and slowed movement. Levodopa serves as a dopamine precursor that can cross the blood-brain barrier and be converted into dopamine inside the brain, helping to replenish the depleted neurotransmitter and improve those motor functions. Carbidopa is included to block peripheral conversion of levodopa to dopamine, which not only increases how much levodopa reaches the brain but also reduces peripheral side effects such as nausea.

The other conditions listed involve different disease mechanisms that are not primarily addressed by dopamine replacement. Alzheimer disease involves cognitive decline with cholinergic/amyloid pathology; multiple sclerosis is an autoimmune demyelinating disorder; amyotrophic lateral sclerosis is a motor neuron disease. Therefore, carbidopa-levodopa is not used for them. Side effects to watch for include dyskinesias and fluctuations in response, but the therapeutic goal remains to improve dopaminergic signaling in Parkinson disease.