Actions of Teva-Emtricitabine/Tenofovir in details
The action of the drug on the human body is called Pharmacodynamics in Medical terminology. To produce its effect and to change the pathological process that is happening the body and to reduce the symptom or cure the disease, the medicine has to function in a specific way. The changes it does to the body at cellular level gives the desired result of treating a disease. Drugs act by stimulating or inhibiting a receptor or an enzyme or a protein most of the times. Medications are produced in such a way that the ingredients target the specific site and bring about chemical changes in the body that can stop or reverse the chemical reaction which is causing the disease.
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Pharmacology:Mechanism of Action: Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)): Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)), a synthetic nucleoside analog of cytidine, is phosphorylated by cellular enzymes to form Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) 5'-triphosphate. Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) 5'-triphosphate inhibits the activity of the HIV-1 reverse transcriptase (RT) by competing with the natural substrate deoxycytidine 5'-triphosphate and by being incorporated into nascent viral DNA which results in chain termination. Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) 5'-triphosphate is a weak inhibitor of mammalian DNA polymerase α, β, & c, and mitochondrial DNA polymerase γ.
Tenofovir (Teva-Emtricitabine/Tenofovir) Disoproxil Fumarate: Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate is an acyclic nucleoside phosphonate diester analog of adenosine monophosphate. Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate requires initial diester hydrolysis for conversion to Tenofovir (Teva-Emtricitabine/Tenofovir), and subsequent phosphorylations by cellular enzymes, to form Tenofovir (Teva-Emtricitabine/Tenofovir) diphosphate. Tenofovir (Teva-Emtricitabine/Tenofovir) diphosphate inhibits the activity of HIV-1 RT by competing with the natural substrate deoxyadenosine 5'-triphosphate and, after incorporation into DNA, by DNA-chain termination. Tenofovir (Teva-Emtricitabine/Tenofovir) diphosphate is a weak inhibitor of mammalian DNA polymerases α, β, and mitochondrial DNA polymerase γ.
Pharmacokinetics: One (1) Teva-Emtricitabine/Tenofovir tablet is bioequivalent to 1 Emtriva capsule 200 mg plus 1 Viread tablet 300 mg following a single-dose administration to fasting healthy subjects (N=39).
Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)): The pharmacokinetic properties of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) are summarized in Table 1. Following oral administration of Emtriva, Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) is rapidly absorbed with peak plasma concentrations occurring at 1-2 hrs post-dose. In vitro binding of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) to human plasma proteins is <4% and is independent of concentration over the range of 0.02-200 mcg/mL. Following administration of radiolabelled Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)), approximately 86% is recovered in the urine and 13% is recovered as metabolites. The metabolites of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) include 3'-sulfoxide diasteriomers and their glucuronic acid conjugate. Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) is eliminated by a combination of glomerular filtrration and active tubular secretion. Following a single oral dose of Emtriva, the plasma Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) half-life is approximately 10 hrs..
Tenofovir (Teva-Emtricitabine/Tenofovir) Disoproxil Fumarate: The pharmacokinetic properties of Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate are summarized in Table 1. Following oral administration of Viread, maximum Tenofovir (Teva-Emtricitabine/Tenofovir) serum concentrations are achieved in 1±0.4 hr. In vitro binding of Tenofovir (Teva-Emtricitabine/Tenofovir) to human plasma proteins is <0.7% and is independent of concentration over the range of 0.01-25 mcg/mL. Approximately 70-80% of the IV dose of Tenofovir (Teva-Emtricitabine/Tenofovir) is recovered as unchanged drug in the urine. Tenofovir (Teva-Emtricitabine/Tenofovir) is eliminated by a combination of glomerular filtration and active tubular secretion. Following a single oral dose of Viread, the terminal elimination half-life of Tenofovir (Teva-Emtricitabine/Tenofovir) is approximately 17 hrs..
Effects of Food on
Oral Absorption:
Teva-Emtricitabine/Tenofovir may be administered with or without food. Administration of Teva-Emtricitabine/Tenofovir following a high fat meal (784 kcal; fat 49 g) or a light meal (373 kcal; fat 8 g) delayed the time of Tenofovir (Teva-Emtricitabine/Tenofovir) Cmax by approximately 0.75 hr. The mean increases in Tenofovir (Teva-Emtricitabine/Tenofovir) AUC and Cmax were approximately 35% and 15% respectively, when administred with a high fat or light meal, compared to administration in the fasted state. In previous safety and efficacy studies, Viread was taken under fed conditions. Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) systemic exposures (AUC and Cmax) were unaffected when Teva-Emtricitabine/Tenofovir was administered with either a high fat or a light meal.
Special Populations: Race: Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)): No pharmacokinetic differences due to race have been identified following the administration of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)).
Tenofovir (Teva-Emtricitabine/Tenofovir) Disoproxil Fumarate: There were insufficient numbers from racial and ethnic groups other than Caucasian to adequately determine potential pharmacokinetic differences among these populations following the administration of Viread.
Gender: Teva-Emtricitabine/Tenofovir Disoproxil Fumarate: Teva-Emtricitabine/Tenofovir pharmacokinetics are similar in male and female patients.
Children and
Elderly:
Pharmacokinetic studies of Tenofovir (Teva-Emtricitabine/Tenofovir) have not been performed in pediatric patients <18 yrs. Pharmacokinetics of Teva-Emtricitabine/Tenofovir have not been fully evaluated in the elderly >65 yrs.
Patients with Renal Impairment: The pharmacokinetics of Teva-Emtricitabine/Tenofovir are altered in patients with renal impairment. In patients with creatinine clearance (CrCl) <50 mL/min, Cmax, and AUC0-∞ of Teva-Emtricitabine/Tenofovir were increased. It is recommended that the dosing interval for Teva-Emtricitabine/Tenofovir be modified in patients with CrCl 30-49 mL/min. Teva-Emtricitabine/Tenofovir should not be used in patients with CrCl <30 mL/min and in patients with end-stage renal disease requiring dialysis.
Patients with Hepatic Impairment: The pharmacokinetics of Tenofovir (Teva-Emtricitabine/Tenofovir) following Viread 300-mg dose have been studied in non-HIV infected patients with moderate to severe hepatic impairment. There were no substantial alterations in Tenofovir (Teva-Emtricitabine/Tenofovir) pharmacokinetics in patients with hepatic impairment compared with unimpaired patients. The pharmacokinetics of Teva-Emtricitabine/Tenofovir or Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) have not been studied in patients with hepatic impairment; however, Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) is not significantly metabolized by liver enzymes, so the impact of liver impairment should be limited.
Drug Interactions : Teva-Emtricitabine/Tenofovir: No drug interaction studies have been conducted using Teva-Emtricitabine/Tenofovir.
Teva-Emtricitabine/Tenofovir Disoproxil Fumarate: The steady state pharmacokinetics of Teva-Emtricitabine/Tenofovir were unaffected, when Teva-Emtricitabine/Tenofovir disoproxil fumarate were administered together versus each agent dosed alone.
In vitro and clinical pharmacokinetic drug-drug interaction studies have shown that the potential for CYP450 mediated interactions involving Teva-Emtricitabine/Tenofovir with other medicinal products is low.
Teva-Emtricitabine/Tenofovir are primarily excreted by the kidneys by a combination of glomerular filtration and active tubular secretion. No drug-drug interactions due to competition for renal excretion have been observed; however, co-administration of Teva-Emtricitabine/Tenofovir with drugs that are eliminated by active tubular secretion may increase concentrations of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)), Tenofovir (Teva-Emtricitabine/Tenofovir), and/or the co-administerd drug.
Drugs that decrease renal function may increase concentrations of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) and/or Tenofovir (Teva-Emtricitabine/Tenofovir).
No clinically significant drug interactions have been observed between Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) and famciclovir, indinavir, stavudine, zidovudine and Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate. Similarly, no clinically significant drug interactions have been observed between Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate and abacavir, adefovir dipivoxil, ribavirin, efavirenz, Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)), indinavir, lamivudine, lopinavir/ritonavir, methadone, oral contraceptives, nelfinavir and saquinavir/ritonavir in studies conducted in healthy volunteers.
Following multiple dosing to HIV-negative subjects receiving either chronic methadone maintenance therapy or oral contraceptives, or single doses of ribavirin, steady-state Tenofovir (Teva-Emtricitabine/Tenofovir) pharmacokinetics were similar to those observed in previous studies, indicating lack of clinically significant drug interactions between these agents and Viread.
Co-administration of Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate with didanosine results in changes in the pharmacokinetics of didanosine that may be of clinical significance. Table 6 summarizes the effects of Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate on the pharmacokinetics of didanosine. Concomitant dosing of Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate with didanosine buffered tablets or enteric-coated capsules significantly increases the Cmax and AUC of didanosine. When didanosine 250-mg enteric-coated capsules were administered with Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate, systemic exposures of didanosine were similar to those seen with the 400-mg enteric-coated capsules alone under fasted conditions. The mechanism of this interaction is unknown.
Clinical Studies: Clinical Study 934 supports the use of Teva-Emtricitabine/Tenofovir tablets for the treatment of HIV-1 infection. Additional data in support of the use of Teva-Emtricitabine/Tenofovir are derived from Study 903, in which lamivudine and Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate were used in combination in treatment-naive adults, and clinical Study 303 in which Emtriva and lamivudine demonstrated comparable efficacy, safety and resistance patterns as part of multidrug regimens. For additional information about these studies, consult the prescribing information of Viread and Emtriva.
Study 934: Emtriva + Viread + Efavirenz compared with Zidovudine/Lamivudine + Efavirenz: Data through 48 weeks are reported for Study 934, a randomized, open-label, active-controlled multicenter study comparing Emtriva + Viread administered in combination with efavirenz versus zidovudine/lamivudine fixed-dose combination administered in combination with efavirenz in 511 antiretroviral-naive patients. Patients had a mean age of 38 years (range 18-80), 86% were male, 59% were Caucasian and 23% were Black. The mean baseline CD4+ cell count was 245 cells/mm3 (range 2-1191) and median baseline plasma HIV-1 RNA was 5.01 log10 copies/mL (range 3.56-6.54). Patients were stratified by baseline CD4+ count (< or ≥200 cells/mm3); 41% had CD4+ cell counts <200 cells/mm3 and 51% of patients had baseline viral loads >100,000 copies/mL. Treatment outcomes through 48 weeks for those patients who did not have efavirenz resistance at baseline are presented in Table 7.
The difference in the proportion of patients who achieved and maintained HIV-1 RNA <400 copies/mL through 48 weeks largely results from the higher number of discontinuations due to adverse events and other reasons in the zidovudine/lamivudine group in this open-label study. In addition, 80% and 70% of patients in the Emtriva + Viread group and the zidovudine/lamivudine group, respectively, achieved and maintained HIV-1 RNA <50 copies/mL. The mean increase from baseline in CD4+ cell count was 190 cells/mm3 in the Emtriva + Viread group and 158 cells/mm3 in the zidovudine/lamivudine group.
Through 48 weeks, 7 patients in the Emtriva + Viread group and 5 patients in the zidovudine/lamivudine group experienced a new CDC-Class C event.
Toxicology:Animal Toxicology:Tenofovir (Teva-Emtricitabine/Tenofovir) and Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate administered in toxicology studies to rats, dogs and monkeys at exposures (based on AUCs) ≥6-fold those observed in humans caused bone toxicity. In monkeys, the bone toxicity was diagnosed as osteomalacia. Osteomalacia observed in monkeys appeared to be reversible upon dose reduction or discontinuation of Tenofovir (Teva-Emtricitabine/Tenofovir). In rats and dogs, the bone toxicity manifested as reduced bone mineral density. The mechanisms underlying bone toxicity is unknown. Evidence of renal toxicity was noted in 4 animal species. Increases in serum creatinine, blood urea nitrogen (BUN), glycosuria, proteinuria, phosphaturia and/or calciuria and decreases in serum phosphate were observed to varying degrees in these animals. These toxicities were noted at exposures (based on AUCs) 2-20 times higher than those observed in humans. The relationship of the renal abnormalities, particularly the phosphaturia, to the bone toxicity is not known.
Microbiology: Antiviral Activity: Teva-Emtricitabine/Tenofovir Disoproxil Fumarate: In combination studies, evaluating the in vivo antiviral activity of Teva-Emtricitabine/Tenofovir together, synergistic antiviral effects were observed.
Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)): The antiviral activity of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) against laboratory and clinical isolates of HIV was assessed in lymphoblastoid cell lines, the MAGI-CCR5 cell line, and peripheral blood mononuclear cells. The 50% effective concentration (EC50) values for Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) were in the range of 0.0013-0.64 micromolar (0.0003-0.158 mcg/mL). In drug combination studies of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) with nucleoside reverse transcriptase inhibitors (NRTIs) (abacavir, lamivudine, stavudine, zalcitabine, zidovudine), non-nucleoside reverse transcriptase inhibitors (NNRTIs) (delavirdine, efavirenz, nevirapine), and protease inhibitors (PIs) (amprenavir, nelfinavir, ritonavir, saquinavir), additive to synergistic effects were observed. Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) displayed antiviral activity in cell culture against HIV-1 clades A, B, C, D, E, F, and G (EC50 values ranged from 0.007-0.075 micromolar) and showed strain-specific activity against HIV-2 (EC50 values ranged from 0.007-1.5 micromolar).
Tenofovir (Teva-Emtricitabine/Tenofovir) Disoproxil Fumarate: The antiviral activity of Tenofovir (Teva-Emtricitabine/Tenofovir) against laboratory and clinical isolates of HIV-1 was assessed in lymphoblastoid cell lines, primary monocyte or macrophage cells and peripheral blood lymphocytes. The EC50 values for Tenofovir (Teva-Emtricitabine/Tenofovir) were in the range of 0.04-8.5 micromolar. In drug combination studies of Tenofovir (Teva-Emtricitabine/Tenofovir) with NRTIs (abacavir, didanosine, lamivudine, stavudine, zalcitabine, zidovudine), NNRTIs (delavirdine, efavirenz, nevirapine), and PIs (amprenavir, indinavir, nelfinavir, ritonavir, saquinavir), additive to synergistic effects were observed. Tenofovir (Teva-Emtricitabine/Tenofovir) displayed antiviral activity in cell culture against HIV-1 clades A, B, C, D, E, F, G, and O (EC50 values ranged from 0.05-2.2 micromolar) and showed strain specific activity against HIV-2 (EC50 values ranged from 1.6-4.9 micromolar).
Resistance: Teva-Emtricitabine/Tenofovir Disoproxil Fumarate: HIV-1 isolates with reduced susceptibility to the combination of Teva-Emtricitabine/Tenofovir have been selected in cell culture. Genotypic analysis of these isolates identified the M184V/I and/or K65R amino acid substitutions in the viral RT.
In a clinical study of treatment-naive patients (Study 934, see Clinical Studies text as follows), resistance analysis was performed on HIV isolates from all virologic failure patients with >400 copies/mL of HIV-1 RNA at Week 48 or early discontinuations. Development of efavirenz resistance-associated mutations occurred most frequently and was similar between the treatment arms. The M184V amino acid substitution, associated with resistance to Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) and lamivudine, was observed in 2/12 (17%) analyzed patient isolates in the Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) + Tenofovir (Teva-Emtricitabine/Tenofovir) group and in 7/22 (32%) analyzed patient isolates in the zidovudine/lamivudine group. Through 48 weeks of Study 934, no patients have developed a detectable K65R mutation in their HIV as analyzed through standard genotypic analysis. Insufficient data are available to assess the development of the K65R mutation upon prolonged exposure to this regimen.
Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)): Emtracitabine-resistant isolates of HIV have been selected in cell culture and in vivo. Genotypic analysis of these isolates showed that the reduced susceptibilty to Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) was associated with a mutation in the HIV RT gene at codon 184, which resulted in an amino acid substitution of methionine by valine or isoleucine (M184V/I).
Tenofovir (Teva-Emtricitabine/Tenofovir) Disoproxil Fumarate: HIV-1 isolates with reduced susceptibility to Tenofovir (Teva-Emtricitabine/Tenofovir) have been selected in cell culture. These viruses expressed a K65R mutation in RT and showed a 2-4 fold reduction in susceptibility to Tenofovir (Teva-Emtricitabine/Tenofovir).
In treatment-naive patients, isolates from 8 patients developed the K65R mutation in the Viread arm through 144 weeks; 7 occurred in the first 48 weeks of treatment and 1 at week 96. In treatment-experienced patients, 14/304 (5%) isolates from patients failing Viread through week 96 showed >1.4 fold (median 2.7) reduced susceptibility to Tenofovir (Teva-Emtricitabine/Tenofovir). Genotypic analysis of the resistant isolates showed a mutation in the HIV-1 RT gene resulting in the K65R amino acid substitution.
Cross-Resistance: Teva-Emtricitabine/Tenofovir Disoproxil Fumarate: Cross-resistance among certain NRTIs has been recognized. The M184V/I and/or K65R susbtitutions selected in cell culture by the combination of Teva-Emtricitabine/Tenofovir are also observed in some HIV-1 isolates from subjects failing treatment with Tenofovir (Teva-Emtricitabine/Tenofovir) in combination with either lamivudine or Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)), and either abacavir or didanosine. Therefore, cross-resistance among these drugs may occur in patients whose virus harbors either or both of these amino acid substitutions.
Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)): Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir))-resistant isolates (M184V/I) were cross-resistant to lamivudine and zalcitabine but retained susceptibility in cell culture to didanosine, stavudine, Tenofovir (Teva-Emtricitabine/Tenofovir), zidovudine, and NNRTIs (delavirdine, efavirenz, and nevirapine). HIV-1 isolates containing the K65R substitution, selected in vivo by abacavir, didanosine, Tenofovir (Teva-Emtricitabine/Tenofovir), and zalcitabine, demonstrated reduced susceptibility to inhibition by Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)). Viruses harboring mutations conferring reduced susceptibility to stavudine and zidovudine (M41L, D67N, K70R, L210W, T215Y/F, K219Q/E), or didanosine (L74V) remained sensitive to Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)). HIV-1 containing the K103N susbtitution associated with resistance to NNRTIs was susceptible to Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)).
Tenofovir (Teva-Emtricitabine/Tenofovir) Disoproxil Fumarate: HIV-1 isolates from patients (N=20) whose HIV-1 expressed a mean of 3 zidovudine-associated RT amino acid substitutions (M41L, D67N, K70R, L210W, T215Y/F, or K219Q/E/N) showed a 3.1-fold decrease in the susceptibility to Tenofovir (Teva-Emtricitabine/Tenofovir). Multinucleoside resistant HIV-1 with a T69S double insertion mutation in the RT showed reduced susceptibility to Tenofovir (Teva-Emtricitabine/Tenofovir).
How should I take Teva-Emtricitabine/Tenofovir?
Take Teva-Emtricitabine/Tenofovir exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered.
Teva-Emtricitabine/Tenofovir comes with a Medication Guide. Read and follow these instructions carefully. Read it again each time you refill your prescription in case there is new information. You should talk to your doctor if you have any questions.
Teva-Emtricitabine/Tenofovir can be taken with or without food.
Keep using Teva-Emtricitabine/Tenofovir for the full time of treatment, even if you or your child begin to feel better. It is also important that you continue taking all of the medicines that your doctor has given you for HIV infection.
Teva-Emtricitabine/Tenofovir works best when there is a constant amount in the blood. To help keep the amount constant, do not miss any doses.
Do not change the dose or stop using Teva-Emtricitabine/Tenofovir without checking first with your doctor. When your supply of Teva-Emtricitabine/Tenofovir is running low, contact your doctor or pharmacist ahead of time. Do not allow yourself to run out of Teva-Emtricitabine/Tenofovir.
Dosing
The dose of Teva-Emtricitabine/Tenofovir will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of Teva-Emtricitabine/Tenofovir. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
For oral dosage form (tablets):
For treatment of HIV infection:
Adults, teenagers, and children 12 years of age and older and weighing 35 kilograms (kg) or over—One tablet once a day. Each tablet contains 200 milligrams (mg) of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) and 300 mg of Tenofovir (Teva-Emtricitabine/Tenofovir).
Children younger than 12 years of age and weighing less than 35 kg—Use and dose must be determined by your doctor.
For prevention of HIV infection (Pre-exposure prophylaxis):
Adults—One tablet once a day. Each tablet contains 200 milligrams (mg) of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) and 300 mg of Tenofovir (Teva-Emtricitabine/Tenofovir).
Children—Use and dose must be determined by your doctor.
Missed Dose
If you miss a dose of Teva-Emtricitabine/Tenofovir, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Storage
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Keep the bottle tightly closed. Keep the medicine in the original bottle that you were given at the pharmacy.
Teva-Emtricitabine/Tenofovir administration
Administration of drug is important to know because the drug absorption and action varies depending on the route and time of administration of the drug. A medicine is prescribed before meals or after meals or along with meals. The specific timing of the drug intake about food is to increase its absorption and thus its efficacy. Few work well when taken in empty stomach and few medications need to be taken 1 or 2 hrs after the meal. A drug can be in the form of a tablet, a capsule which is the oral route of administration and the same can be in IV form which is used in specific cases. Other forms of drug administration can be a suppository in anal route or an inhalation route.
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Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.
Use Teva-Emtricitabine/Tenofovir regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.
To be sure this medication is helping your condition and not causing harmful effects, your blood will need to be tested often. Your kidney and liver function or bone density may also need to be tested. Visit your doctor regularly.
If you have hepatitis B you may develop liver symptoms after you stop taking this medication, even months after stopping. Your doctor may want to check your liver function for several months after you stop using Teva-Emtricitabine/Tenofovir. Visit your doctor regularly.
HIV/AIDS is usually treated with a combination of drugs. Use all medications as directed by your doctor. Read the medication guide or patient instructions provided with each medication. Do not change your doses or medication schedule without your doctor's advice. Every person with HIV or AIDS should remain under the care of a doctor.
Store in the original container at room temperature, away from moisture and heat.
Teva-Emtricitabine/Tenofovir pharmacology
Pharmacokinetics of a drug can be defined as what body does to the drug after it is taken. The therapeutic result of the medicine depends upon the Pharmacokinetics of the drug. It deals with the time taken for the drug to be absorbed, metabolized, the process and chemical reactions involved in metabolism and about the excretion of the drug. All these factors are essential to deciding on the efficacy of the drug. Based on these pharmacokinetic principles, the ingredients, the Pharmaceutical company decides dose and route of administration. The concentration of the drug at the site of action which is proportional to therapeutic result inside the body depends on various pharmacokinetic reactions that occur in the body.
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For additional information on Mechanism of Action, Antiviral Activity, Resistance and Cross Resistance, please consult the EMTRIVA and VIREAD prescribing information.
Mechanism Of Action
Teva-Emtricitabine/Tenofovir is a fixed-dose combination of antiviral drugs Teva-Emtricitabine/Tenofovir disoproxil fumarate.
Pharmacokinetics
Teva-Emtricitabine/Tenofovir: One Teva-Emtricitabine/Tenofovir tablet was bioequivalent to one EMTRIVA capsule (200 mg) plus one VIREAD tablet (300 mg) following single-dose administration to fasting healthy subjects (N=39).
Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)): The pharmacokinetic properties of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) are summarized in Table 7. Following oral administration of EMTRIVA, Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) is rapidly absorbed with peak plasma concentrations occurring at 1–2 hours post-dose. Less than 4% of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) binds to human plasma proteins in vitro and the binding is independent of concentration over the range of 0.02–200 μg/mL. Following administration of radiolabelled Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)), approximately 86% is recovered in the urine and 13% is recovered as metabolites. The metabolites of Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) include 3'-sulfoxide diastereomers and their glucuronic acid conjugate. Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) is eliminated by a combination of glomerular filtration and active tubular secretion. Following a single oral dose of EMTRIVA, the plasma Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) half-life is approximately 10 hours.
Tenofovir (Teva-Emtricitabine/Tenofovir) Disoproxil Fumarate: The pharmacokinetic properties of Tenofovir (Teva-Emtricitabine/Tenofovir) disoproxil fumarate are summarized in Table 7. Following oral administration of VIREAD, maximum Tenofovir (Teva-Emtricitabine/Tenofovir) serum concentrations are achieved in 1.0 ± 0.4 hour. Less than 0.7% of Tenofovir (Teva-Emtricitabine/Tenofovir) binds to human plasma proteins in vitro and the binding is independent of concentration over the range of 0.01–25 μg/mL. Approximately 70–80% of the intravenous dose of Tenofovir (Teva-Emtricitabine/Tenofovir) is recovered as unchanged drug in the urine. Tenofovir (Teva-Emtricitabine/Tenofovir) is eliminated by a combination of glomerular filtration and active tubular secretion. Following a single oral dose of VIREAD, the terminal elimination half-life of Tenofovir (Teva-Emtricitabine/Tenofovir) is approximately 17 hours.
Table 7 : Single Dose Pharmacokinetic Parameters for Teva-Emtricitabine/Tenofovir in AdultsIncludes lost to follow-up, subject withdrawal, noncompliance, protocol violation and other reasons.
Through Week 48, 84% and 73% of subjects in the Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) + Tenofovir (Teva-Emtricitabine/Tenofovir) DF group and the zidovudine/lamivudine group, respectively, achieved and maintained HIV-1 RNA < 400 copies/mL (71% and 58% through Week 144). The difference in the proportion of subjects who achieved and maintained HIV-1 RNA < 400 copies/mL through 48 weeks largely results from the higher number of discontinuations due to adverse events and other reasons in the zidovudine/lamivudine group in this open-label trial. In addition, 80% and 70% of subjects in the Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) + Tenofovir (Teva-Emtricitabine/Tenofovir) DF group and the zidovudine/lamivudine group, respectively, achieved and maintained HIV-1 RNA < 50 copies/mL through Week 48 (64% and 56% through Week 144). The mean increase from baseline in CD4+ cell count was 190 cells/mm³ in the Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) + Tenofovir (Teva-Emtricitabine/Tenofovir) DF group and 158 cells/mm³ in the zidovudine/lamivudine group at Week 48 (312 and 271 cells/mm³ at Week 144).
Through 48 weeks, 7 subjects in the Emtricitabine (Teva-Emtricitabine/Tenofovir (Teva-Emtricitabine/Tenofovir)) + Tenofovir (Teva-Emtricitabine/Tenofovir) DF group and 5 subjects in the zidovudine/lamivudine group experienced a new CDC Class C event (10 and 6 subjects through 144 weeks).
iPrEx Trial
The iPrEx trial was a randomized double-blind placebo-controlled multinational study evaluating Teva-Emtricitabine/Tenofovir in 2499 HIV-seronegative men or transgender women who have sex with men and with evidence of high risk behavior for HIV-1 infection. Evidence of high risk behavior included any one of the following reported to have occurred up to six months prior to study screening: no condom use during anal intercourse with an HIV-1 positive partner or a partner of unknown HIV status; anal intercourse with more than 3 sex partners; exchange of money, gifts, shelter or drugs for anal sex; sex with male partner and diagnosis of sexually transmitted infection; no consistent use of condoms with sex partner known to be HIV-1 positive.
All subjects received monthly HIV-1 testing, risk-reduction counseling, condoms and management of sexually transmitted infections. Of the 2499 enrolled, 1251 received Teva-Emtricitabine/Tenofovir and 1248 received placebo. The mean age of subjects was 27 years, 5% were Asian, 9% Black, 18% White, and 72% Hispanic/Latino.
Subjects were followed for 4237 person-years. The primary outcome measure for the study was the incidence of documented HIV seroconversion. At the end of treatment, emergent HIV-1 seroconversion was observed in 131 subjects, of which 48 occurred in the Teva-Emtricitabine/Tenofovir group and 83 occurred in the placebo group, indicating a 42% (95% CI: 18–60%) reduction in risk. Risk reduction was found to be higher (53%; 95% CI: 34– 72%) among subjects who reported previous unprotected anal intercourse (URAI) at screening (732 and 753 subjects reported URAI within the last 12 weeks at screening in the Teva-Emtricitabine/Tenofovir and placebo groups, respectively). In a post-hoc case control study of plasma and intracellular drug levels in about 10% of study subjects, risk reduction appeared to be the greatest in subjects with detectable intracellular Tenofovir (Teva-Emtricitabine/Tenofovir). Efficacy was therefore strongly correlated with adherence.
Partners PrEP Trial
The Partners PrEP trial was a randomized, double-blind, placebo-controlled 3 arm trial conducted in 4758 serodiscordant heterosexual couples in Kenya and Uganda to evaluate the efficacy and safety of TDF (N=1589) and FTC/TDF (N=1583) versus (parallel comparison) placebo (N=1586), in preventing HIV-1 acquisition by the uninfected partner.
All subjects received monthly HIV-1 testing, evaluation of adherence, assessment of sexual behavior, and safety evaluations. Women were also tested monthly for pregnancy. Women who became pregnant during the trial had study drug interrupted for the duration of the pregnancy and while breastfeeding. The uninfected partner subjects were predominantly male (61–64% across study drug groups), and had a mean age of 33–34 years.
Following 7827 person-years of follow up, 82 emergent HIV-1 seroconversions were reported, with an overall observed seroincidence rate of 1.05 per 100 person-years. Of the 82 seroconversions, 13 and 52 occurred in partner subjects randomized to Teva-Emtricitabine/Tenofovir and placebo, respectively. Two of the 13 seroconversions in the Teva-Emtricitabine/Tenofovir arm and 3 of the 52 seroconversions in the placebo arm occurred in women during treatment interruptions for pregnancy. The risk reduction for Teva-Emtricitabine/Tenofovir relative to placebo was 75% (95% CI: 55–87%). In a post-hoc case control study of plasma drug levels in about 10% of study subjects, risk reduction appeared to be the greatest in subjects with detectable plasma Tenofovir (Teva-Emtricitabine/Tenofovir). Efficacy was therefore strongly correlated with adherence.
References
DailyMed. "EMTRICITABINE: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". https://dailymed.nlm.nih.gov/dailyme... (accessed September 17, 2018).
NCIt. "Emtricitabine: NCI Thesaurus (NCIt) provides reference terminology for many systems. It covers vocabulary for clinical care, translational and basic research, and public information and administrative activities.". https://ncit.nci.nih.gov/ncitbrowser... (accessed September 17, 2018).
EPA DSStox. "Emtricitabine: DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology.". https://comptox.epa.gov/dashboard/ds... (accessed September 17, 2018).
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