Comparative Pharmacology
Head-to-head clinical analysis: SYMFI versus SYMFI LO.
Peer-Reviewed Evidence
Head-to-head clinical analysis: SYMFI versus SYMFI LO.
SYMFI vs SYMFI LO
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Symfi is a combination of efavirenz, lamivudine, and tenofovir disoproxil fumarate. Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that binds reversibly to HIV-1 reverse transcriptase, causing a conformational change and inhibiting RNA-directed DNA polymerase activity. Lamivudine is a nucleoside reverse transcriptase inhibitor (NRTI) that is phosphorylated intracellularly to its active triphosphate metabolite, which competes with deoxycytidine triphosphate for incorporation into viral DNA, causing chain termination. Tenofovir disoproxil fumarate is an acyclic nucleotide analog NRTI that, after hydrolysis to tenofovir and subsequent phosphorylation, inhibits HIV reverse transcriptase by competing with deoxyadenosine triphosphate and causing DNA chain termination.
SYMFI LO is a fixed-dose combination of efavirenz, lamivudine, and tenofovir disoproxil fumarate. Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that binds reversibly to the HIV-1 reverse transcriptase enzyme, causing a conformational change that inhibits RNA- and DNA-dependent DNA polymerase activities. Lamivudine and tenofovir disoproxil fumarate are nucleoside analogue reverse transcriptase inhibitors (NRTIs); they are phosphorylated to active metabolites that compete with natural substrates and incorporate into viral DNA, causing chain termination.
SYMFI (efavirenz/lamivudine/tenofovir disoproxil fumarate) fixed-dose combination: one tablet (600 mg efavirenz/300 mg lamivudine/300 mg tenofovir disoproxil fumarate) orally once daily on an empty stomach, preferably at bedtime.
One tablet (efavirenz 600 mg/lamivudine 300 mg/tenofovir disoproxil fumarate 300 mg) orally once daily on an empty stomach, preferably at bedtime.
None Documented
None Documented
Terminal elimination half-life is approximately 8-12 hours in patients with normal renal function. This supports twice-daily dosing in clinical practice.
Efavirenz: 40-55 hours (single dose), 52-76 hours (multiple doses); clinically permits once-daily dosing. Emtricitabine: 10 hours; supports once-daily dosing. Tenofovir disoproxil fumarate: 17 hours (tenofovir intracellular half-life ~60 hours); long intracellular persistence.
Approximately 90% of the administered dose is excreted unchanged in the urine via glomerular filtration and tubular secretion. Less than 5% is eliminated via feces.
Efavirenz: ~34% renal (1% unchanged, rest as metabolites), ~61% fecal (16% unchanged). Emtricitabine: ~86% renal (70% unchanged), ~14% fecal. Tenofovir disoproxil fumarate: ~70-80% renal as unchanged tenofovir via glomerular filtration and active tubular secretion.
Category C
Category C
Antiretroviral NNRTI-Based Combination
Antiretroviral NNRTI-Based Combination