Fozivudine tidoxil is a thioether lipid–Zidovudine (ZDV) conjugate. After intake it is split intracellularly into the lipid moiety and ZDV-monophosphate, which is subsequently phosphorylated to the active metabolite ZDV-triphosphate. The rationale behind the development of fozivudine (FZD) was to take advantage of the high cleavage activity in mononuclear cells and other organs resulting in increased amounts of intracellular ZDV available for phosphorylation to the active metabolite, and a very low activity in red blood and stem cells, which should result in reduced haematologic toxicity. It is member of the family of nucleoside reverse transcriptase (RT) inhibitors. Fozivudine tidoxil has been in Phase II clinical trials for the treatment of HIV infection. There were three adverse events possibly related to fozivudine: urine abnormality, gastrointestinal pain and abnormal dreams.