Zalcitabine can cause severe peripheral neuropathy (use with extreme caution in pre-existing peripheral neuropathy; avoid use in moderate or severe peripheral neuropathy; use with caution in risk for developing peripheral neuropathy). Potentially fatal pancreatitis may occur. Cases of fatal lactic acidosis and severe hepatomegaly with steatosis may occur (use with extreme caution in hepatic impairment and in risk factors for liver disease). Hepatic failure and death (may be related to underlying hepatitis B) reported (rare). Oral ulceration and rare esophageal ulcers reported. Use with caution in renal dysfunction. Multiple potentially serious drug interactions exist. Use with caution in history of heart failure (cardiomyopathy and heart failure reported). Fat redistribution and accumulation observed in patients receiving antiretroviral agents (causal relationship not established).