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Tenofovir Disoproxil Fumarate


General


Pronunciation

(ten OF oh vir dye soe PROX il FUE ma rate)


Brand Names: U.S.

  • Viread

Indications


Use: Labeled Indications

Chronic hepatitis B: Treatment of chronic hepatitis B virus (HBV) in patients ≥12 years of age

HIV infection: In combination with other antiretroviral agents for the treatment of HIV-1 infection in adults and pediatric patients ≥2 years of age


Contraindications


US labeling: There are no contraindications listed in the manufacturers labeling.

Canadian labeling: Hypersensitivity to tenofovir or any component of the formulation


ALERT: U.S. Boxed Warning

Lactic acidosis/severe hepatomegaly with steatosis:

Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs in combination with other antiretrovirals.

Posttreatment exacerbation of hepatitis:

Severe acute exacerbations of hepatitis have been reported in hepatitis B virus (HBV) " “infected patients who have discontinued anti " “hepatitis B therapy. Monitor hepatic function closely with clinical and laboratory follow-up for at least several months in patients who discontinue anti " “hepatitis B therapy. If appropriate, resumption of anti " “hepatitis B therapy may be warranted.


Dosing and Administration


Dosing: Adult

Hepatitis B infection: Oral: 300 mg once daily

Note: Tenofovir is recommended for first-line treatment of HBV (Lok 2009). Concurrent use with adefovir and/or tenofovir combination products should be avoided.

Treatment duration (AASLD practice guidelines 2009):

Note: Patients not achieving <2 log decrease in serum HBV DNA after at least 6 months of therapy should either receive additional treatment or be switched to an alternative therapy (Lok, 2009).

Hepatitis Be antigen (HBeAg) positive chronic hepatitis: Treat ≥1 year until HBeAg seroconversion and undetectable serum HBV DNA; continue therapy for ≥6 months after HBeAg seroconversion

HBeAg negative chronic hepatitis: Treat >1 year until hepatitis B surface antigen (HBsAg) clearance

Decompensated liver disease: Lifelong treatment is recommended

HIV infection: Oral: 300 mg once daily (in combination with other antiretrovirals). Note: Tenofovir is a component of recommended initial regimens in treatment-naive patients (when coadministered with emtricitabine plus dolutegravir, with emtricitabine plus darunavir/ritonavir, or with emtricitabine plus raltegravir; lamivudine may be substituted for emtricitabine in any of these regimens) and is a component of a recommended initial regimen in treatment-naive patients with pre-ART CrCl >70 mL/minute (when coadministered with emtricitabine plus elvitegravir/cobicistat) (HHS [adult] 2015).


Dosing: Geriatric

Refer to adult dosing.


Dosing: Pediatric

Hepatitis B infection: Oral: Children ≥12 years (and ≥35 kg) and Adolescents: Refer to adult dosing. Note: Canadian labeling does not approve of use in patients <18 years of age.

HIV infection: Oral:

Children 2 to <12 years: 8 mg/kg once daily (maximum: 300 mg once daily) (in combination with other antiretrovirals). Note: Canadian labeling does not approve of use in children <12 years of age.

Dosing recommendations based on body weight if using the oral powder: Note: One level scoop of powder = 40 mg tenofovir

10 to <12 kg: 80 mg once daily

12 to <14 kg: 100 mg once daily

14 to <17 kg: 120 mg once daily

17 to <19 kg: 140 mg once daily

19 to <22 kg: 160 mg once daily

22 to <24 kg: 180 mg once daily

24 to <27 kg: 200 mg once daily

27 to <29 kg: 220 mg once daily

29 to <32 kg: 240 mg once daily

32 to <34 kg: 260 mg once daily

34 to <35 kg: 280 mg once daily

≥35 kg: 300 mg once daily

Dosing recommendations based on body weight if using the oral tablets:

17 to <22 kg: 150 mg once daily

22 to <28 kg: 200 mg once daily

28 to <35 kg: 250 mg once daily

≥35 kg: 300 mg once daily

Children ≥12 years (and ≥35 kg) and Adolescents: Refer to adult dosing. Note: Tenofovir is a component of recommended initial regimens in adolescent treatment-naive patients (when coadministered with emtricitabine plus dolutegravir, with emtricitabine plus darunavir/ritonavir, or with emtricitabine plus raltegravir; lamivudine may be substituted for emtricitabine in any of these regimens) and is a component of a recommended initial regimen in adolescent treatment-naive patients with pre-ART CrCl >70 mL/minute (when coadministered with emtricitabine plus elvitegravir/cobicistat) (HHS [adult] 2015).


Dosing: Renal Impairment

Adults: Note: Use of powder formulation has not been evaluated in renal impairment.

Manufacturers labeling:

CrCl ≥50 mL/minute: No dosage adjustment necessary.

CrCl 30-49 mL/minute: 300 mg every 48 hours

CrCl 10-29 mL/minute: 300 mg every 72-96 hours

CrCl <10 mL/minute without hemodialysis: No dosage adjustment provided in manufacturer 's labeling; has not been studied.

Hemodialysis: 300 mg following dialysis every 7 days or after a total of ~12 hours of dialysis (usually once weekly assuming 3 dialysis sessions lasting about 4 hours each).

Alternate recommendations (IDSA [Lucas 2014]):

CrCl <50 mL/minute (and not on hemodialysis) or GFR <60 mL/minute/1.73 m2: Avoid use

Peritoneal dialysis: Use with caution; dose reduction recommended (no specific adjustment provided)

Children: No dosage adjustment provided in manufacturer 's labeling (has not been studied).


Dosing: Hepatic Impairment

No dosage adjustment necessary.


Administration

Tablets may be administered without regard to meals. Powder should be mixed with 2-4 ounces of soft food (applesauce, baby food, yogurt) and swallowed immediately (avoids bitter taste); do not mix in liquid (powder may float on top of the liquid even after stirring). Measure powder using only the supplied dosing scoop.


Dietary Considerations

Consider calcium and vitamin D supplementation.


Storage

Store at 25 ‚ °C (77 ‚ °F); excursions are permitted between 15 ‚ °C and 30 ‚ °C (59 ‚ °F and 86 ‚ °F). Dispense only in original container.


Dosage Forms/Strengths


Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Powder, Oral, as disoproxil fumarate:

Viread: 40 mg/g (60 g)

Tablet, Oral, as disoproxil fumarate:

Viread: 150 mg, 200 mg, 250 mg

Viread: 300 mg [contains fd&c blue #2 aluminum lake]


Drug Interactions

Acyclovir-Valacyclovir: May increase the serum concentration of Tenofovir Products. Tenofovir Products may increase the serum concentration of Acyclovir-Valacyclovir. Monitor therapy

Adefovir: May diminish the therapeutic effect of Tenofovir Products. Adefovir may increase the serum concentration of Tenofovir Products. Tenofovir Products may increase the serum concentration of Adefovir. Avoid combination

Aminoglycosides: May increase the serum concentration of Tenofovir Products. Tenofovir Products may increase the serum concentration of Aminoglycosides. Monitor therapy

Atazanavir: Tenofovir Disoproxil Fumarate may decrease the serum concentration of Atazanavir. Atazanavir may increase the serum concentration of Tenofovir Disoproxil Fumarate. Management: Must use ritonavir-boosting in adults; give combo (atazanavir/ritonavir 300mg/100mg and tenofovir 300mg) as a single daily dose with food. Pediatric patients, pregnant patients, and users of H2-blockers require other dose changes. Consider therapy modification

Cabozantinib: MRP2 Inhibitors may increase the serum concentration of Cabozantinib. Monitor therapy

Cidofovir: May increase the serum concentration of Tenofovir Products. Tenofovir Products may increase the serum concentration of Cidofovir. Monitor therapy

Cobicistat: May enhance the adverse/toxic effect of Tenofovir Products. More specifically, cobicistat may impair proper tenofovir monitoring and dosing. Monitor therapy

Darunavir: Tenofovir Disoproxil Fumarate may increase the serum concentration of Darunavir. Darunavir may increase the serum concentration of Tenofovir Disoproxil Fumarate. Monitor therapy

Diclofenac (Systemic): May enhance the nephrotoxic effect of Tenofovir Products. Management: Seek alternatives to this combination whenever possible. Avoid use of tenofovir with multiple NSAIDs or any NSAID given at a high dose. Consider therapy modification

Didanosine: Tenofovir Disoproxil Fumarate may diminish the therapeutic effect of Didanosine. Tenofovir Disoproxil Fumarate may increase the serum concentration of Didanosine. Management: Avoid concomitant treatment with tenofovir disoproxil fumarate and didanosine. Consider altering even existing, stable treatment to avoid this combination. Avoid combination

Ganciclovir-Valganciclovir: Tenofovir Products may increase the serum concentration of Ganciclovir-Valganciclovir. Ganciclovir-Valganciclovir may increase the serum concentration of Tenofovir Products. Monitor therapy

Ledipasvir: May increase the serum concentration of Tenofovir Disoproxil Fumarate. Management: Avoidance of this combination is recommended under some circumstances. Refer to full monograph for details. Consider therapy modification

Lopinavir: May enhance the nephrotoxic effect of Tenofovir Disoproxil Fumarate. Lopinavir may increase the serum concentration of Tenofovir Disoproxil Fumarate. Monitor therapy

Nonsteroidal Anti-Inflammatory Agents: May enhance the nephrotoxic effect of Tenofovir Products. Management: Seek alternatives to these combinations whenever possible. Avoid use of tenofovir with multiple NSAIDs or any NSAID given at a high dose. Consider therapy modification

Simeprevir: Tenofovir Disoproxil Fumarate may decrease the serum concentration of Simeprevir. Simeprevir may increase the serum concentration of Tenofovir Disoproxil Fumarate. Monitor therapy

Telaprevir: May increase the serum concentration of Tenofovir Disoproxil Fumarate. Monitor therapy

Tipranavir: Tenofovir Disoproxil Fumarate may decrease the serum concentration of Tipranavir. Tipranavir may decrease the serum concentration of Tenofovir Disoproxil Fumarate. Monitor therapy

TiZANidine: CYP1A2 Inhibitors (Weak) may increase the serum concentration of TiZANidine. Management: Avoid these combinations when possible. If combined use cannot be avoided, initiate tizanidine at an adult dose of 2 mg and increase in 2-4 mg increments based on patient response. Monitor for increased effects of tizanidine, including adverse reactions. Consider therapy modification

Velpatasvir: May increase the serum concentration of Tenofovir Disoproxil Fumarate. Monitor therapy


Monitoring Parameters

Patients with HIV: CBC with differential, reticulocyte count, creatine kinase, CD4 count, HIV RNA plasma levels, serum phosphorus; serum creatinine (prior to initiation and as clinically indicated during therapy), urine glucose and urine protein (in patients at risk for renal impairment or who experienced renal impairment while taking adefovir), hepatic function tests, bone density (patients with a history of bone fracture or have risk factors for bone loss); testing for HBV is recommended prior to the initiation of antiretroviral therapy; weight (children)

Patients with HBV: HIV status (prior to initiation of therapy); serum phosphorus; serum creatinine (prior to initiation and as clinically indicated during therapy), urine glucose and urine protein (in patients at risk for renal impairment or who experienced renal impairment while taking adefovir); bone density (patients with a history of bone fracture or have risk factors for bone loss); HBV DNA (every 3-6 months during therapy); HBeAg and anti-HBe; LFTs every 3 months during therapy and for several months following discontinuation of tenofovir; signs/symptoms of HBV relapse/exacerbation following discontinuation of therapy

Patients with HIV and HBV coinfection should be monitored for several months following tenofovir discontinuation.


Adverse Reactions


Includes data from both treatment-naive and treatment-experienced HIV patients and in chronic hepatitis B.

>10%:

Central nervous system: Insomnia (3% to 18%), headache (5% to 14%), pain (12% to 13%), dizziness (8% to 13%), depression (4% to 11%)

Dermatologic: Skin rash (includes maculopapular, pustular, or vesiculobullous rash; pruritus; or urticaria: 5% to 18%), pruritus (16%)

Endocrine & metabolic: Hypercholesterolemia (19% to 22%), increased serum triglycerides (1% to 4%)

Gastrointestinal: Abdominal pain (4% to 22%), nausea (8% to 20%), diarrhea (9% to 16%), vomiting (2% to 13%)

Neuromuscular & skeletal: Decreased bone mineral density (28%; ≥5% at spine or ≥7% at hip), increased creatine phosphokinase (2% to 12%), weakness (6% to 11%)

Miscellaneous: Fever (4% to 11%)

1% to 10%:

Cardiovascular: Chest pain (3%)

Central nervous system: Fatigue (9%), anxiety (6%), peripheral neuropathy (1% to 5%)

Dermatologic: Diaphoresis (3%)

Endocrine & metabolic: Weight loss (2% to 4%), glycosuria (grades 3/4: ≤3%), hyperglycemia (grades 3/4: 2% to 3%), lipodystrophy (1%)

Gastrointestinal: Increased serum amylase (grades 3/4: 4% to 9%), anorexia (3% to 4%), dyspepsia (3% to 4%), flatulence (3% to 4%)

Genitourinary: Hematuria ( ≤grades 3/4: 3% to 7%)

Hematologic & oncologic: Neutropenia (3%)

Hepatic: Increased serum ALT (2% to 10%), increased serum AST (3% to 5%), increased serum transaminases (2% to 5%), increased serum alkaline phosphatase (1%)

Neuromuscular & skeletal: Back pain (4% to 9%), arthralgia (5%), myalgia (4%)

Renal: Increased serum creatinine (9%), renal failure (7%)

Respiratory: Sinusitis (8%), upper respiratory tract infection (8%), nasopharyngitis (5%), pneumonia (2% to 5%)

Postmarketing and/or case reports: Angioedema, exacerbation of hepatitis B (following discontinuation), Fanconi 's syndrome, hepatitis, hypersensitivity reaction, hypokalemia, hypophosphatemia, immune reconstitution syndrome, increased gamma-glutamyl transferase, interstitial nephritis, lactic acidosis, myopathy, nephrogenic diabetes insipidus, nephrotoxicity, osteomalacia, pancreatitis, polyuria, proteinuria, proximal tubular nephropathy, renal insufficiency, renal tubular necrosis, rhabdomyolysis, severe hepatomegaly with steatosis


Warnings/Precautions


Special Populations: Renal Function Impairment

In patients with CrCl <50 mL/minute or with ESRD requiring dialysis, Cmax and AUC of tenofovir were increased. Following a single 300 mg dose, a 4-hour hemodialysis session removed ~10% of the administered tenofovir dose.


Warnings/Precautions

Concerns related to adverse effects:

- Decreased bone mineral density: In clinical trials, use has been associated with decreases in bone mineral density in HIV-1 infected adults and increases in bone metabolism markers. Serum parathyroid hormone and 1,25 vitamin D levels were also higher. Decreases in bone mineral density have also been observed in clinical trials of HIV-1 infected pediatric patients. Observations in chronic hepatitis B infected pediatric patients (aged 12-18 years) were similar. In all pediatric clinical trials, skeletal growth (height) appears unaffected. Consider monitoring of bone density in adult and pediatric patients with a history of pathologic fractures or with other risk factors for bone loss or osteoporosis. Consider calcium and vitamin D supplementation for all patients; effect of supplementation has not been studied but may be beneficial. Long-term bone health and fracture risk unknown. If abnormalities are suspected, expert assessment is recommended.

- Fat redistribution: May cause redistribution of fat (eg, buffalo hump, peripheral wasting with increased abdominal girth, cushingoid appearance).

- Immune reconstitution syndrome: Patients may develop immune reconstitution syndrome resulting in the occurrence of an inflammatory response to an indolent or residual opportunistic infection during initial HIV treatment or activation of autoimmune disorders (eg, Graves ' disease, polymyositis, Guillain-Barre syndrome) later in therapy; further evaluation and treatment may be required.

- Lactic acidosis/hepatomegaly: [US Boxed Warning]: Lactic acidosis and severe hepatomegaly with steatosis have been reported with tenofovir and other nucleoside analogues, including fatal cases; use with caution in patients with risk factors for liver disease (risk may be increased with female gender, obesity, pregnancy or prolonged nucleoside exposure) and suspend treatment in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or hepatotoxicity (transaminase elevation may/may not accompany hepatomegaly and steatosis).

- Osteomalacia and renal dysfunction: May cause osteomalacia with proximal renal tubulopathy. Bone pain, extremity pain, fractures, arthralgias, weakness and muscle pain have been reported. In patients at risk for renal dysfunction, persistent or worsening bone or muscle symptoms should be evaluated for hypophosphatemia and osteomalacia.

- Pancreatitis: Pancreatitis has been reported; use with caution in patients with a prior history or risk factors for pancreatitis. Discontinue if pancreatitis is suspected.

- Renal toxicity: May cause renal toxicity (acute renal failure and/or Fanconi syndrome); avoid use with concurrent or recent nephrotoxic therapy (including high dose or multiple NSAID use). Acute renal failure has occurred in HIV-infected patients with risk factors for renal impairment who were on a stable tenofovir regimen to which a high dose or multiple NSAID therapy was added. Consider alternatives to NSAIDS in patients taking tenofovir and at risk for renal impairment. Calculate estimated creatinine clearance prior to initiation of therapy and monitor renal function (including recalculation of creatinine clearance and serum phosphorus) during therapy. In patients at risk for renal dysfunction, including patients who have experienced renal events while taking adefovir, assess serum phosphorus, urine glucose, and urine protein prior to and periodically during treatment. Dosage adjustment required in patients with CrCl <50 mL/minute. Use with caution in patients with low body weight or concurrent medications that increase tenofovir levels. IDSA guidelines recommend discontinuing tenofovir (and substituting with alternative antiretroviral therapy) in HIV-infected patients who develop a decline in GFR (a >25% decrease in GFR from baseline and to a level of <60 mL/minute/1.73 m2) during use, particularly in presence of proximal tubular dysfunction (eg, euglycemic glycosuria, increased urinary phosphorus excretion and hypophosphatemia, proteinuria [new onset or worsening]) (IDSA [Lucas 2014]).

Disease-related concerns:

- Chronic hepatitis B: [US Boxed Warning]: Severe, acute exacerbation of hepatitis B may occur upon discontinuation. Monitor liver function several months after discontinuing treatment; reinitiation of antihepatitis B therapy may be required. Treatment of HBV in patients with unrecognized/untreated HIV may lead to HIV resistance; patients should be tested for presence of HIV infection prior to initiating therapy

- Hepatic impairment: Use with caution in patients with hepatic impairment. Limited data supporting treatment of chronic hepatitis B in patients with decompensated liver disease; observe for increased adverse reactions, including renal dysfunction.

- Renal impairment: Tenofovir is predominately eliminated renally. Use with caution in patients with renal impairment (CrCl <50 mL/minute); dosage adjustment required. IDSA guidelines recommend avoiding tenofovir in HIV patients with preexisting kidney disease (CrCl <50 mL/minute and not on hemodialysis or GFR <60 mL/minute/1.73 m2) when other effective HIV treatment options exist because data suggest risk of chronic kidney disease (CKD) is increased (IDSA [Lucas 2014]).

Concurrent drug therapy issues:

- Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

- Tenofovir combination products: Do not use concurrently with tenofovir combination products (ie, Atripla, Complera, Stribild, Truvada).

Special populations:

- Elderly: Use with caution in the elderly. Dosage adjustment based on renal function may be required.

- Pediatric: Decreases in bone mineral density may occur; long term effects are unknown. Skeletal growth (height) appears to be unaffected in tenofovir-treated children and adolescents.

Other warnings/precautions:

- Appropriate use: Hepatitis B coinfection: Treatment of HIV in patients with unrecognized/untreated hepatitis B virus (HBV) may lead to rapid HBV resistance. Patients should be tested for presence of chronic hepatitis B infection prior to initiation of therapy. In patients coinfected with HIV and HBV, an appropriate antiretroviral combination should be selected due to HIV resistance potential; these patients should receive tenofovir dosed for HIV therapy.

- Appropriate use: HIV treatment: Do not use as monotherapy in treatment of HIV. Clinical trials in HIV-infected patients whose regimens contained only three nucleoside reverse transcriptase inhibitors (NRTI) show less efficacy, early virologic failure and high rates of resistance substitutions. Use three NRTI regimens with caution and monitor response carefully. Triple drug regimens with two NRTIs in combination with a non-nucleoside reverse transcriptase inhibitor or a HIV-1 protease inhibitor are usually more effective.


Pregnancy Risk Factor

B


Pregnancy Considerations

Adverse events were observed in some animal reproduction studies. Tenofovir has a high level of transfer across the human placenta. Intrauterine growth has not been affected in human studies, but data is conflicting about potential growth effects later in infancy. Clinical studies in children have shown bone demineralization with chronic use. Bone mineral content was also decreased in infants following in utero exposure. No increased risk of overall birth defects has been observed following first trimester exposure according to data collected by the antiretroviral pregnancy registry. Cases of lactic acidosis/hepatic steatosis syndrome related to mitochondrial toxicity have been reported with use of nucleoside analogues. In addition, these adverse events are similar to other rare but life-threatening syndromes which occur during pregnancy (eg, HELLP syndrome). In general nucleoside reverse transcriptase inhibitors are well tolerated and the benefits of use generally outweigh potential risk. The HHS Perinatal HIV Guidelines consider tenofovir in combination with either emtricitabine or lamivudine to be a preferred NRTI backbone for use in antiretroviral-naive pregnant women. The HHS Perinatal HIV Guidelines consider emtricitabine plus tenofovir, or lamivudine plus tenofovir as recommended dual NRTI/NtRTI backbones for HIV/HBV coinfected pregnant women. Hepatitis B flare may occur if tenofovir is discontinued postpartum. Limited data indicate decreased maternal exposure during the third trimester; dose adjustments are not needed.

Combination antiretroviral therapy (cART) therapy is recommended for all HIV-infected pregnant women. The goal of therapy is to keep the viral load below the limit of detection and prevent perinatal transmission. Therapy must be individualized. In general, women who become pregnant on a stable cART regimen may continue that regimen if viral suppression is effective, contraindications for use in pregnancy are not present, and the regimen is well tolerated. For HIV-infected couples planning a pregnancy, maximum viral suppression with cART is recommended prior to conception for the HIV-infected partner(s). When HIV is diagnosed during pregnancy in a woman who has never received antiretroviral therapy, cART should be considered as soon as possible after diagnosis to reduce the risk of perinatal transmission. If antiretroviral drug-resistance testing is done, treatment may be started prior to obtaining results, then adjusted accordingly. Monitoring during pregnancy is more frequent than in non-pregnant adults. If cART must be interrupted for <24 hours, stop then restart all medications simultaneously in order to decrease the chance of developing resistance. Long-term follow-up is recommended for all infants exposed to antiretroviral medications; children who develop significant organ system abnormalities (particularly of the CNS or heart) should be evaluated for potential mitochondrial dysfunction.

HIV-infected women not planning a pregnancy may use any available type of contraception, considering possible drug interactions and contraindications of the specific method. In addition, consistent use of condoms is also recommended (even during pregnancy) to prevent transmission of HIV or other sexually-transmitted diseases.

Health care providers are encouraged to enroll pregnant women exposed to antiretroviral medications as early in pregnancy as possible in the Antiretroviral Pregnancy Registry (1-800-258-4263 or www.APRegistry.com). Health care providers caring for HIV-infected women and their infants may contact the National Perinatal HIV Hotline (888-448-8765) for clinical consultation (HHS [perinatal] 2016).


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Pharmacology

Tenofovir disoproxil fumarate (TDF), a nucleotide reverse transcriptase inhibitor, is an analog of adenosine 5-monophosphate; it interferes with the HIV viral RNA dependent DNA polymerase resulting in inhibition of viral replication. TDF is first converted intracellularly by hydrolysis to tenofovir and subsequently phosphorylated to the active tenofovir diphosphate. Tenofovir inhibits replication of HBV by inhibiting HBV polymerase.


Distribution

Vd: 1.2-1.3 L/kg


Metabolism

Tenofovir disoproxil fumarate (TDF) is converted intracellularly by hydrolysis (by non-CYP enzymes) to tenofovir, then phosphorylated to the active tenofovir diphosphate


Excretion

Urine (70% to 80%) via filtration and active secretion, primarily as unchanged tenofovir within 72 hours; after multiple oral doses (administered with food): 32% ‚ ± 10% is excreted in the urine within 24 hours

Clearance: Total body clearance is decreased in patients with renal impairment


Time to Peak

Serum: Fasting: 36-84 minutes; With high-fat meal: 96-144 minutes


Half-Life Elimination

Serum: 17 hours; intracellular: 10 to 50 hours


Protein Binding

<7% to serum proteins


Patient and Family Education


Patient Education

- Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

- Patient may experience headache, dizziness, nausea, vomiting, diarrhea, insomnia, or loss of strength and energy. Have patient report immediately to prescriber signs of liver problems (dark urine, feeling tired, lack of appetite, nausea, abdominal pain, light-colored stools, vomiting, or yellow skin or eyes), signs of kidney problems (urinary retention, blood in urine, change in amount of urine passed, or weight gain), signs of too much lactic acid in the blood (lactic acidosis; fast breathing, fast heartbeat, abnormal heartbeat, vomiting, drowsiness, shortness of breath, feeling very tired or weak, severe dizziness, feeling cold, or muscle pain or cramps), depression, bone pain, muscle pain, muscle weakness, painful extremities, change in body fat, or sign of infection (HCAHPS).

- Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

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