It is discovered that efavirenz (L-743726) may suppress a panel of mutant viruses resistant to nonnucleoside reverse transcriptase inhibitors (NNRTIs) that express a single RT amino acid substitution, with 95% inhibitory doses of ≤ 1.5μM. When efavirenz is examined for its ability to inhibit different polymerase enzymes, it is discovered that it lacks activity (IC50>300μM). Several wild-type T-lymphoid cell line-adapted variations are efficiently inhibited by efavirenz. In primary lymphoid and monocytoid cell cultures, wild-type primary isolates of the virus exhibit the same activity (IC95, 1.5 to 3.0 nM). Furthermore, HIV-1 genotypes that contain RT amino acid changes, which confer resistance to other NNRTIs, are effectively inhibited by efavirenz. for comparative purposes [1]. With an IC50 of 60 nM, efavirenz is a non-nucleoside analog reverse transcriptase inhibitor (NNRTI)[2]. With an IC50 of 17 nM, efavirenz inhibits synthesis utilizing an RNA PPT-primed substrate[3].

Efavirenz (L-743726) is eliminated from rats quickly after intravenous injection, but it is eliminated from monkeys much more slowly. In both species, the large volume of distribution (two to four times the body water content) suggests extensive tissue binding. Rats have a 16% oral bioavailability. After giving an intravenous dose of 1 mg/kg of Efavirenz, the half-life in monkeys was more than 2.5 hours. Orally, efavirenz is well absorbed. Plasma levels are consistently high when oral doses administered as fine suspensions in 0.5% aqueous methylcellulose are given to monkeys. Approximately 3.0 hours after a dose of 2.0 mg/kg, peak levels of 0.5μM are achieved. According to estimates, the absolute bioavailability is 42%. A plasma peak level of 3.22 μM is obtained with a dose of 10 mg/kg. One chimpanzee received an oral dose of 10 mg/kg, which resulted in plasma concentrations of 4.12, 2.95, and 2.69 μM at 2, 8, and 24 hours after dosing, respectively[1].

Absorption, Distribution and Excretion
Nearly all of the urinary excretion of the radiolabeled drug was in the form of metabolites.
Oral bioavailability of efavirenz may be affected by administration with food. Administration of a single 600-mg dose of efavirenz as capsules with a high-fat, high-calorie meal (894 kcal, 54 g fat, 54% of calories from fat) or a reduced-fat, normal-calorie meal (440 kcal, 2 g fat, 4% of calories from fat) increases peak plasma concentrations of the drug by 39 or 51%, respectively, and AUC by 22 or 17%, respectively, compared with administration in the fasting state. Administration of a single 600-mg dose of efavirenz as tablets with a high-fat, high-calorie meal (approximately 1000 kcal, 500-600 kcal from fat) increases peak plasma concentrations and AUC of the drug by 79 and 28%, respectively, compared with administration in the fasting state.
Efavirenz is excreted principally in the feces, both as unchanged drug and metabolites. Excretion of efavirenz has been evaluated in individuals receiving 400 mg daily for 1 month. Following oral administration of 400 mg of radiolabeled efavirenz on day 8, 14-34% of the dose was excreted in urine (less than 1% as unchanged drug), and 16-61% was excreted in feces (predominantly as unchanged drug).
Efavirenz is about 99.5-99.75% bound to plasma proteins, principally albumin.
In HIV-infected adults receiving efavirenz 200, 400, or 600 mg once daily, peak plasma concentrations of the drug generally occur in 3-5 hours and steady-state plasma concentrations are achieved in 6-10 days. Following continued administration of efavirenz, plasma concentrations are lower than expected from single-dose studies, presumably because of increased clearance of the drug. In one study in individuals receiving efavirenz 200-400 mg once daily for 10 days, plasma concentrations of the drug were 22-42% lower than those predicted from single-dose studies. Following oral administration of efavirenz 600 mg once daily in HIV-infected adults, peak plasma concentration, trough plasma concentration, and AUC of the drug at steady-state averaged 4.1 mcg/mL, 1.8 mcg/mL, and 58. mcg*hour/mL, respectively.
For more Absorption, Distribution and Excretion (Complete) data for EFAVIRENZ (8 total), please visit the HSDB record page.

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Metabolism / Metabolites
Efavirenz is principally metabolized by the cytochrome P450 system to hydroxylated metabolites with subsequent glucuronidation of these hydroxylated metabolites. These metabolites are essentially inactive against HIV-1.
Efavirenz was metabolized extensively by all the species as evidenced by the excretion of none or trace quantities of parent compound in urine. Significant species differences in the metabolism of efavirenz were observed. The major metabolite excreted in the urine of all species was the O-glucuronide conjugate (M1) of the 8-hydroxylated metabolite. Efavirenz was also metabolized by direct conjugation with glucuronic acid, forming the N-glucuronide (M2) in all five species. The sulfate conjugate of 8-OH efavirenz (M3) was found in the urine of rats and cynomolgus monkeys but not in humans. In addition to the aromatic ring-hydroxylated products, metabolites with a hydroxylated cyclopropane ring (at C14) were also isolated. GSH-related products of efavirenz were identified in rats and guinea pigs. The cysteinylglycine adduct (M10), formed from the GSH adduct (M9), was found in significant quantities in only rat and guinea pig urine and was not detected in other species. In vitro metabolism studies were conducted to show that the GSH adduct was produced from the cyclopropanol intermediate (M11) in the presence of only rat liver and kidney subcellular fractions and was not formed by similar preparations from humans or cynomolgus monkeys. These studies indicated the existence of a specific glutathione-S-transferase in rats capable of metabolizing the cyclopropanol metabolite (M11) to the GSH adduct, M9.
Efavirenz is a substrate for cytochrome p450 isoforms, particularly CYP3A4 and CYP2B6. The 8-hydroxy metabolite is excreted in the urine, and the glucuronide conjugate of 8-hydroxy-efavirenz is present in plasma and urine. Sixty percent of the dose is excreted in urine as the glucuronide conjugate.
Efavirenz has known human metabolites that include 8-hydroxyefavirenz.

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Biological Half-Life
40-55 hours
The terminal elimination half-life of efavirenz is prolonged in patients with chronic liver disease. Following oral administration of a single 400-mg dose of efavirenz, an elimination half-life of 152 or 118 hours was reported in individuals with or without chronic liver disease, respectively.
The terminal elimination half-life of efavirenz reported in single-dose studies is longer than that reported in multiple-dose studies and has averaged 52-76 hours after a single oral dose and 40-55 hours following administration of 200-400 mg daily for 10 days.

Interactions
Alcohol abuse complicates treatment of HIV disease and is linked to poor outcomes. Alcohol pharmacotherapies, including disulfiram (DIS), are infrequently utilized in co-occurring HIV and alcohol use disorders possibly related to concerns about drug interactions between antiretroviral (ARV) medications and DIS. This pharmacokinetics study (n?=?40) examined the effect of DIS on efavirenz (EFV), ritonavir (RTV), or atazanavir (ATV) and the effect of these ARV medications on DIS metabolism and aldehyde dehydrogenase (ALDH) activity which mediates the DIS-alcohol reaction. EFV administration was associated with decreased S-Methyl-N-N-diethylthiocarbamate (DIS carbamate), a metabolite of DIS (p?=?.001) and a precursor to the metabolite responsible for ALDH inhibition, S-methyl-N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO). EFV was associated with increased DIS inhibition of ALDH activity relative to DIS alone administration possibly as a result of EFV-associated induction of CYP 3A4 which metabolizes the carbamate to DETC-MeSO (which inhibits ALDH). Conversely, ATV co-administration reduced the effect of DIS on ALDH activity possibly as a result of ATV inhibition of CYP 3A4. DIS administration had no significant effect on any ARV studied.
Administration of efavirenz in patients receiving psychoactive drugs may result in increased CNS effects.
Efavirenz may decrease the plasma concentrations of amprenavir; no specific dosage adjustment can be recommended until additional studies are conducted.
Efavirenz may inhibit the metabolism of these medications /astemizole or cisapride/ through competition for the CYP3A4 isoenzyme, which may increase the potential for cardiac arrhythmias; use is contraindicated.
For more Interactions (Complete) data for EFAVIRENZ (15 total), please visit the HSDB record page.

[1]. L-743, 726 (DMP-266): a novel, highly potent nonnucleoside inhibitor of the human immunodeficiency virus type 1 reverse transcriptase. Antimicrob Agents Chemother. 1995 Dec;39(12):2602-5.

[2]. Differential susceptibility of HIV-1 reverse transcriptase to inhibition by RNA aptamers in enzymatic reactions monitoring specific steps during genome replication. J Biol Chem. 2006 Sep 1;281(35):25712-22.

[3]. HIV-1 reverse transcriptase plus-strand initiation exhibits preferential sensitivity to non-nucleoside reverse transcriptase inhibitors in vitro. J Biol Chem. 2007 Mar 16;282(11):8005-10.

Therapeutic Uses
Anti-HIV Agents; Reverse Transcriptase Inhibitors
Due to ongoing neuropsychiatric adverse events in some efavirenz (EFV)-treated patients, a switch to an alternative non-nucleoside reverse transcriptase inhibitor may be considered. Rilpivirine (RPV) has been coformulated as a single-tablet regimen (STR) with emtricitabine/tenofovir disoproxil fumarate (FTC/TDF), and the components have demonstrated noninferior efficacy to EFV+FTC/TDF, good tolerability profile, and high adherence. After discontinuation, EFV has an extended inductive effect on cytochrome P450 (CYP) 3A4 that, after switching, may reduce RPV exposures and adversely impact clinical outcomes. This study examines the clinical implications of reduced RPV exposures with concomitant FTC/TDF and declining EFV exposures when patients, intolerant to EFV, switch from EFV/FTC/TDF to RPV/FTC/TDF. This 48-week, phase 2b, open-label, multicenter study evaluated the efficacy and safety of switching from EFV/FTC/TDF (>/= 3 months duration) to RPV/FTC/TDF. Virologic suppression (HIV-1 RNA <50 copies/mL), safety, and EFV and RPV pharmacokinetics were assessed. At weeks 12 and 24, all 49 dosed subjects remained suppressed on RPV/FTC/TDF. At week 48, 46 (93.9%) subjects remained suppressed and virologic failure occurred in 2/49 (4.1%) subjects with no emergence of resistance. EFV concentrations were above the 90th percentile for inhibitory concentration (IC90) for several weeks after EFV discontinuation, and RPV exposures were in the range observed in phase 3 studies by approximately 2 weeks post switch. No subjects discontinued the study due to an adverse event. Switching from EFV/FTC/TDF to RPV/FTC/ TDF was a safe, efficacious option for virologically suppressed HIV-infected patients with EFV intolerance wishing to remain on an STR.
Efavirenz is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection. /Included in US product labeling/

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Drug Warnings
To report a case of acquired long QT syndrome that, after exclusion of all other possible causes, was probably related to therapy with efavirenz, a novel nonnucleoside reverse transcriptase inhibitor.
About 53% of adults receiving efavirenz (600 mg once daily) in controlled clinical studies reported adverse CNS effects such as abnormal dreams, abnormal thinking, agitation, amnesia, confusion, depersonalization, dizziness, euphoria, hallucinations, impaired concentration, insomnia, somnolence, and stupor; these adverse effects were reported in 25% of adults in the control groups not receiving efavirenz. These effects were described as mild (do not interfere with daily activities) in 33.3%, moderate (may interfere with daily activities) in 17.4%, or severe (interrupt usual daily activities) in 2% of patients receiving efavirenz and required discontinuance of the drug in 2.1%. Dizziness was reported in 28.1% and insomnia was reported in 16.3% of patients receiving the drug. Impaired concentration, somnolence, or abnormal dreams were reported in 6.2-8.3% and hallucinations were reported in 1.2% of patients.
Serious adverse psychiatric symptoms have been reported rarely in adults receiving efavirenz. Severe depression, suicidal ideation, nonfatal suicide attempts, aggressive behavior, paranoid reactions, or manic reactions have been reported in 0.4-1.6% of patients receiving efavirenz in controlled clinical studies; these psychiatric symptoms were reported in up to 0.6% of those in the control groups not receiving the drug. The incidence of each of these psychiatric symptoms ranges from 0.3% (for manic reactions) to 2% (for severe depression or suicidal ideation) in patients with a prior history of psychiatric disorders, and these individuals appear to be at greater risk of such symptoms than other individuals. Other psychiatric symptoms reported in controlled clinical studies in adults receiving efavirenz include depression (15.8%), anxiety (11.1%), and nervousness (6.3%); these symptoms were reported in 13.1, 7.6, or 2%, respectively, of those in the control groups not receiving the drug. Although a causal relationship with efavirenz has not been established, there have been occasional postmarketing reports of death by suicide, delusions, or psychosis-like behavior in patients receiving efavirenz. In addition, aggressive reactions, agitation, emotional lability, mania, neurosis,and paranoia have been reported during postmarketing surveillance. There is no evidence that patients who develop adverse CNS effects (e.g., dizziness, insomnia, impaired concentration, abnormal dreams) during efavirenz therapy are at greater risk of developing psychiatric symptoms.
Fatigue has been reported in up to 7% of adults receiving efavirenz in clinical studies. Other adverse nervous system effects reported during postmarketing surveillance include abnormal coordination, ataxia, seizures, hypoesthesia, paresthesia, neuropathy, and tremor. Adverse CNS effects occurred in 18% of children receiving efavirenz in clinical studies.
For more Drug Warnings (Complete) data for EFAVIRENZ (21 total), please visit the HSDB record page.

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Pharmacodynamics
Efavirenz (dideoxyinosine, ddI) is an oral non-nucleoside reverse transcriptase inhibitor (NNRTI). It is a synthetic purine derivative and, similar to zidovudine, zalcitabine, and stavudine. Efavirenz was originally approved specifically for the treatment of HIV infections in patients who failed therapy with zidovudine. Currently, the CDC recommends that Efavirenz be given as part of a three-drug regimen that includes another nucleoside reverse transcriptase inhibitor (e.g., lamivudine, stavudine, zidovudine) and a protease inhibitor or efavirenz when treating HIV infection.

C14H9CLF3NO2

315.67

315.027

154598-52-4

(Rac)-Efavirenz-d4;1246812-58-7;Efavirenz-d5;1132642-95-5;Efavirenz-13C6;1261394-62-0

64139

White to off-white solid powder

1.5±0.1 g/cm3

422.7±55.0 °C at 760 mmHg

139-141ºC

209.4±31.5 °C

0.0±1.1 mmHg at 25°C

1.582

3.72

1

5

1

21

519

1

C1CC1C#C[C@]2(C3=C(C=CC(=C3)Cl)NC(=O)O2)C(F)(F)F

XPOQHMRABVBWPR-ZDUSSCGKSA-N

InChI=1S/C14H9ClF3NO2/c15-9-3-4-11-10(7-9)13(14(16,17)18,21-12(20)19-11)6-5-8-1-2-8/h3-4,7-8H,1-2H2,(H,19,20)/t13-/m0/s1

(4S)-6-chloro-4-(2-cyclopropylethynyl)-4-(trifluoromethyl)-1H-3,1-benzoxazin-2-one

DMP-266, DMP 266; Efavirenz; Sustiva; Stocrin; DMP-266; DMP 266; trade name: efavirenz; L-743,726; L-743726; DMP266; EFV; L 743726

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.08 mg/mL (6.59 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (6.59 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (6.59 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)