Valacyclovir should be avoided in which patients due to risk of severe thrombocytopenic syndromes?

• A. Pregnancy
• B. Immunocompromised
• C. Diabetes
• D. Renal failure

Answer: (B)

Valacyclovir can, in rare cases, cause immune-mediated thrombocytopenia and thrombotic microangiopathy (such as TTP/HUS), leading to a dangerous drop in platelets. This risk is markedly higher in people with compromised immune systems, where immune regulation is disrupted and hematologic toxicity from antiviral therapy is more likely. Because of this, avoiding valacyclovir in immunocompromised patients helps prevent potentially life-threatening bleeding and organ complications. Renal failure would require dose adjustments due to drug clearance, but the question focuses on the specific risk of severe thrombocytopenic syndromes linked to immune status, which makes immunocompromised the most implicated group.