Fill in the blank _________ inhibits the enzyme nitric oxide synthase, which could theoretically contribute to sexual dysfunction, especially in men. This SSRI is also notorious for causing withdrawal reactions upon sudden discontinuation, with symptoms such as akathisia, restlessness, gastrointestinal symptoms, dizziness, and tingling, especially when suddenly discontinued from long-term high-dose treatment.

A. Citalopram: Citalopram has minimal effects on nitric oxide synthase and is less likely to cause severe withdrawal symptoms compared to paroxetine. It is generally considered one of the better-tolerated SSRIs. B. Sertraline: Sertraline can cause mild withdrawal symptoms but does not significantly inhibit nitric oxide synthase, making it less associated with sexual dysfunction than paroxetine. C. Venlafaxine: Venlafaxine is an SNRI, not a pure SSRI. While it can cause withdrawal symptoms, it does not strongly inhibit nitric oxide synthase, and its sexual side effects are typically due to serotonergic activity rather than nitric oxide inhibition. D. Paroxetine: Paroxetine strongly inhibits nitric oxide synthase, contributing to sexual dysfunction in men. It also has a short half-life, making it the SSRI most associated with withdrawal symptoms such as dizziness, restlessness, and sensory disturbances when abruptly stopped.