TEMIXYS
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TEMIXYS (TEMIXYS).
Temixys is a fixed-dose combination of tenofovir disoproxil fumarate (a nucleotide reverse transcriptase inhibitor) and lamivudine (a nucleoside reverse transcriptase inhibitor). Tenofovir diphosphate and lamivudine triphosphate inhibit HIV-1 reverse transcriptase by competing with natural substrates and causing DNA chain termination.
| Metabolism | Tenofovir DF is hydrolyzed to tenofovir and then phosphorylated to tenofovir diphosphate; minimal hepatic metabolism via CYP450 enzymes. Lamivudine is phosphorylated intracellularly to lamivudine triphosphate; minimally metabolized in the liver (5-10%) via oxidation. |
| Excretion | Biliary/fecal: approximately 70% unchanged; renal: less than 1% unchanged; about 30% as metabolites in feces. |
| Half-life | 41 hours (mean terminal elimination half-life); range 32-50 hours; supports once-daily dosing. |
| Protein binding | Greater than 99% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Approximately 3.3 L/kg (mean); indicates extensive tissue distribution. |
| Bioavailability | Oral bioavailability approximately 80%; with food, no significant change. |
| Onset of Action | Not applicable; oral tablet, no immediate clinical effect. |
| Duration of Action | Approximately 24 hours; consistent with once-daily dosing; clinical effect persists throughout dosing interval. |
| Molecular Weight | Bictegravir: 449.4 Da; Emtricitabine: 247.2 Da; Tenofovir alafenamide: 476.6 Da |
Temixys (tenofovir disoproxil fumarate 300 mg / emtricitabine 200 mg) fixed-dose combination: one tablet orally once daily with or without food.
| Dosage form | TABLET |
| Renal impairment | Not recommended if CrCl < 30 mL/min. For CrCl 30–49 mL/min: administer one tablet every 48 hours. For CrCl ≥ 50 mL/min: standard dose. |
| Liver impairment | No dose adjustment required for mild or moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C); use caution. |
| Pediatric use | Approved for pediatric patients weighing ≥ 35 kg with adequate renal function: one tablet orally once daily. Not recommended for weight < 35 kg due to inability to adjust individual components. |
| Geriatric use | No specific dose adjustment recommended; select dose with caution due to higher frequency of decreased renal function, monitor renal function closely. |
| 1st trimester | No adequate studies in pregnant women; use only if benefit outweighs risk. No evidence of teratogenicity in animal studies. |
| 2nd trimester | Use with caution; monitor fetal growth and maternal viral load. No known harm reported. |
| 3rd trimester | Use if needed; minimal risk of adverse fetal outcomes. Long-term safety data limited. |
Clinical note
Comprehensive clinical and safety monograph for TEMIXYS (TEMIXYS).
| Placental transfer | Bictegravir, emtricitabine, and tenofovir alafenamide cross the placenta in humans; emtricitabine and tenofovir reach comparable concentrations in fetal and maternal blood. |
| Breastfeeding | Not recommended during breastfeeding due to potential for HIV transmission via breast milk and unknown excretion of bictegravir/emtricitabine/tenofovir alafenamide into human milk. |
■ FDA Black Box Warning
Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs. Post-treatment acute exacerbations of hepatitis B have been reported in patients co-infected with HIV-1 and HBV who discontinued lamivudine or tenofovir DF. Hepatic function should be monitored closely in these patients.
| Serious Effects |
Hypersensitivity to any componentConcurrent use with dofetilideConcurrent use with rifampin
| Precautions | Lactic acidosis and severe hepatomegaly with steatosis, Exacerbation of hepatitis B upon discontinuation, New onset or worsening renal impairment, Decrease in bone mineral density, Immune reconstitution syndrome, Fat redistribution/accumulation |
| Food/Dietary | No significant food interactions; take with or without food. Avoid alcohol as it may increase the risk of hepatotoxicity. |
Loading safety data…
| Lactation Rating |
| L5 |
| Teratogenic Risk | Teratogenic risk not fully characterized; insufficient human data. In animal studies, no teratogenic effects observed at clinically relevant exposures. For HIV/HBV treatment, avoid use in first trimester unless benefit outweighs risk; if used, monitor for neural tube defects. Second and third trimester risks are low but data limited. |
| Fetal Monitoring | Monitor maternal renal function, liver function, and HIV/HBV viral load. Perform fetal ultrasound for neural tube defects if exposed in first trimester. Assess infant for adverse effects including renal and bone toxicity if maternal use during pregnancy. |
| Fertility Effects | No published human studies on fertility. In animal studies, no impairment of fertility or reproductive performance at up to 3.3 times human exposure for tenofovir alafenamide and emtricitabine. |
| Clinical Pearls | Temixys (abacavir/lamivudine) is a fixed-dose combination for HIV-1 infection. Screen for HLA-B*5701 allele before initiating abacavir; if positive, do not use due to risk of hypersensitivity reaction. Monitor for hepatotoxicity and lactic acidosis, especially in women and obese patients. Adjust dose in renal impairment (CrCl <50 mL/min requires separate dosing of components). |
| Patient Advice | Take one tablet daily with or without food. · Report any rash, fever, or gastrointestinal symptoms immediately as they may indicate abacavir hypersensitivity. · Do not stop taking this medication without consulting your doctor, as HIV may become resistant. · Regular blood tests are needed to monitor kidney function and viral load. · Avoid alcohol while taking this medication to reduce the risk of liver problems. |