Europe. The European
Medicines Evaluation Agency (EMEA) has issued a public statement about the efficacy and safety of tenofovir and didanosine co-administration.(1) The statement refers to new reports of virological failure and emergence of resistance following co-administration of these two medicines as observed in several clinical studies: tenofovir disoproxil fumarate and didanosine were co-administered with a non-nucleoside reverse transcriptase inhibitor in HIVinfected treatment-naïve adult patients with high baseline viral load and low CD4 cell counts. Similar reports had been previously observed with this dual combination in the context of triple combination therapy with a nucleoside/ nucleotide reverse transcriptase inhibitor and were the subject of recommendations by the EMEA on 22 October 2003.(2) A WHO Drug Alert was also issued on this information.(3) The precise nature of any interaction leading to non-response is still not known. Based on the new clinical data the EMEA notes that:
• The co-administration of tenofovir disoproxil fumarate and didanosine is not recommended within any antiretroviral combination therapy, and particularly in patients with high viral load and low CD4 cell count.
• Rare, sometimes fatal cases of pancreatitis and lactic acidosis have been reported with the co-administration of tenofovir and didanosine.
• If this combination is considered to be strictly necessary, patients should be closely monitored for efficacy and didanosinerelated adverse events.
The Product Information for tenofovir disoproxil fumarate (Viread) has now been modified to reflect the above-mentioned information.
1. EMEA Public Statement EMEA/62331/2005, 3 March 2005. Available on the internet at www.emea.eu.int
2. EMEA Public Statement EMEA/CPMP/5094/03, 22 October 2003. Available on the internet at www.emea.eu.int
3. WHO Drug Alert 109, 24 October 2003. Available on the internet at www.who.int/medicines/library/ drugalert