Which first-generation antipsychotic drug is known for causing irreversible pigmentation of the retina with chronic use?

Thioridazine is the first-generation antipsychotic drug known for causing irreversible pigmentation of the retina, particularly when used over long periods. This side effect is associated with its active metabolite, which can deposit in the retinal tissues, leading to potential vision changes.

The significance of monitoring patients on thioridazine relates to the risk of developing retinal issues, which can be particularly concerning for long-term users. Patients may not be aware of these potential effects until they experience visual disturbances, making it crucial for healthcare providers to perform regular eye examinations for patients prescribed this medication.

In contrast, the other medications listed—valproate, lamotrigine, and baclofen—are not first-generation antipsychotics and do not share the same risk of causing irreversible retina pigmentation. Valproate is primarily used for mood stabilization and seizure disorders. Lamotrigine is an anticonvulsant that can also be used for bipolar disorder, and baclofen is a muscle relaxant primarily indicated for spasticity. Due to their different mechanisms and indications, they do not have the retinal side effects associated with thioridazine.