Symfi and Symfi Lo are both three-drug combinations of efavirenz, lamivudine and tenofovir disoproxil fumarate (TDF) for the treatment of HIV-1 infection. The difference between Symfi and Symfi Lo is the amount of efavirenz contained in each product.

Symfi Lo contains a reduced dose of efavirenz (to help lower side effects) while Symfi has a dose similar to other efavirenz products already on the market.

Specifically, Symfi Lo contains a 400 mg dose of efavirenz, one-third less than the 600 mg dose of efavirenz found in Symfi. In the ENCORE1 study, 400 mg efavirenz was found to be of comparable effectiveness to 600 mg of efavirenz when combined with tenofovir and emtricitabine in adults with HIV-1 infection who had never undergone treatment.

Symfi and Symfi Lo both contain

• efavirenz (Sustiva), a non-nucleoside reverse transcriptase inhibitor
• lamivudine (Epivir), a nucleo(t)side reverse transcriptase inhibitor
• tenofovir disoproxil fumarate (Viread), a nucleo(t)side reverse transcriptase inhibitor

Both Symfi and Symfi Lo are being marketed as cost-saving products from Mylan Pharmaceuticals, with list prices discounted significantly to wholesale costs of similar HIV medications on the market.