Final answer:
The adverse effect of baclofen in a client with multiple sclerosis is increased muscle spasms.
Step-by-step explanation:
The adverse effect of baclofen in a client with multiple sclerosis is increased muscle spasms (a).
Baclofen is a muscle relaxant commonly used to manage spasticity in individuals with multiple sclerosis. However, in some cases, it can paradoxically cause muscle spasms and increased muscle tone. This happens because baclofen acts on GABA receptors in the spinal cord, inhibiting the release of excitatory neurotransmitters and reducing muscle contraction. However, if the dosage is too high or if the drug is abruptly discontinued, it can lead to rebound muscle spasticity.