Lamivudine

Lamivudine tablets (HBV) are indicated for the treatment of chronic hepatitis B virus (HBV) infection associated with evidence of hepatitis B viral replication and active liver inflammation [see Clinical Studies ( 14.1 , 14.2 )]. The following points should be considered when initiating therapy with lamivudine tablets (HBV):

• Due to high rates of resistance development in treated patients, initiation of treatment with lamivudine tablets (HBV) should only be considered when the use of an alternative antiviral agent with a higher genetic barrier to resistance is not available or appropriate.
• Lamivudine tablets (HBV) have not been evaluated in patients co-infected with human immunodeficiency virus (HIV), hepatitis C virus (HCV), or hepatitis delta virus.
• Lamivudine tablets (HBV) have not been evaluated in liver transplant recipients or in patients with chronic hepatitis B virus infection with decompensated liver disease. Lamivudine tablets (HBV) are a nucleoside analogue reverse transcriptase inhibitor indicated for the treatment of chronic hepatitis B virus (HBV) infection associated with evidence of hepatitis B viral replication and active liver inflammation. ( 1 )

• Lamivudine tablets (HBV): 100 mg are pink colored, capsule shaped, biconvex, film coated tablets, debossed with ‘37’ on one side and ‘I’ on the other side.
• Tablets: 100 mg ( 3 )

Lamivudine tablets (HBV) are contraindicated in patients with a previous hypersensitivity reaction to lamivudine. Lamivudine tablets (HBV) is contraindicated in patients with previous hypersensitivity reaction to lamivudine. (4)

• Emergence of Resistance-Associated HBV Substitutions: Consider a switch to an alternative regimen if serum HBV DNA remains detectable after 24 weeks of treatment. ( 2.6 , 5.3 )
• Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues. ( 5.4 )

5.1 Exacerbations of Hepatitis after Discontinuation of Treatment Clinical and laboratory evidence of exacerbations of hepatitis have occurred after discontinuation of lamivudine. These exacerbations have been detected primarily by serum ALT elevations in addition to re-emergence of HBV DNA commonly observed after stopping treatment; see Table 4 for more information regarding frequency of posttreatment ALT elevations [see Adverse Reactions (6.1) ]. Although most events appear to have been self-limited, fatalities have been reported in some cases. The causal relationship to discontinuation of lamivudine treatment is unknown. Patients should be closely monitored with both clinical and laboratory follow-up for at least several months after stopping treatment with lamivudine tablets (HBV). There is insufficient evidence to determine whether re-initiation of lamivudine tablets (HBV) alters the course of posttreatment exacerbations of hepatitis.

5.2 Risk of HIV-1 Resistance if lamivudine tablets (HBV) is Used in Patients with Unrecognized or Untreated HIV-1 Infection Lamivudine tablets (HBV) contain a lower lamivudine dose than the lamivudine dose used to treat HIV-1 infection with lamivudine tablets and oral solution or with lamivudine- containing antiretroviral fixed-dose combination products. Lamivudine tablets (HBV) is not appropriate for patients co-infected with HBV and HIV-1. If a patient with unrecognized or untreated HIV-1 infection is prescribed lamivudine tablets (HBV) for the treatment of HBV, rapid emergence of HIV-1 resistance is likely to result because of the sub therapeutic dose and the inappropriate use of monotherapy for HIV-1 treatment. HIV counseling and testing should be offered to all patients before beginning treatment with lamivudine tablets (HBV) and periodically during treatment because of the risk of rapid emergence of resistant HIV-1 and limitation of treatment options if lamivudine tablets (HBV) is prescribed to treat chronic hepatitis B in a patient who has unrecognized or untreated HIV-1 infection or who acquires HIV-1 infection during treatment.

5.3 Emergence of Resistance-Associated HBV Substitutions In controlled clinical trials, YMDD-mutant HBV was detected in subjects with on– lamivudine tablets (HBV) re-appearance of HBV DNA after an initial decline below the assay limit [see Microbiology (12.4) ]. Subjects treated with lamivudine tablets (HBV) (adults and children) with YMDD-mutant HBV at 52 weeks showed diminished treatment responses in comparison with subjects treated with lamivudine tablets (HBV) without evidence of YMDD substitutions, including the following: lower rates of HBeAg seroconversion and HBeAg loss (no greater than placebo recipients), more frequent return of positive HBV DNA, and more frequent ALT elevations. In the controlled trials, when subjects developed YMDD-mutant HBV, they had a rise in HBV DNA and ALT from their previous on-treatment levels. Progression of hepatitis B, including death, has been reported in some subjects with YMDD-mutant HBV, including subjects from the liver transplant setting and from other clinical trials. In order to reduce the risk of resistance in patients receiving monotherapy with lamivudine tablets (HBV), a switch to an alternative regimen should be considered if serum HBV DNA remains detectable after 24 weeks of treatment. Optimal therapy should be guided by resistance testing.

5.4 Lactic Acidosis and Severe Hepatomegaly with Steatosis Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues, including lamivudine tablets (HBV). A majority of these cases have been in women. Female sex and obesity may be risk factors for the development of lactic acidosis and severe hepatomegaly with steatosis in patients treated with antiretroviral nucleoside analogues. Most of these reports have described patients receiving nucleoside analogues for treatment of HIV infection, but there have been reports of lactic acidosis in patients receiving lamivudine for hepatitis B. Treatment with lamivudine tablets (HBV) should be suspended in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations.

The following adverse reactions are discussed in other sections of the labeling:

• Exacerbations of hepatitis B after discontinuation of treatment [see Warnings and Precautions (5.1) ].
• Risk of emergence of resistant HIV-1 infection [see Warnings and Precautions (5.2) ].
• Risk of emergence of resistant HBV infection [see Warnings and Precautions (5.3) ].
• Lactic acidosis and severe hepatomegaly with steatosis [see Warnings and Precautions (5.4) ]. The most common reported adverse reactions in those receiving lamivudine tablets (HBV) (incidence greater than or equal to 10% and reported at a rate greater than placebo) were ear, nose, and throat infections; sore throat; and diarrhea. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Hetero Labs Limited at 1-866-495-1995 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. Clinical Trials Experience in Adult Subjects with Chronic HBV Infection Clinical adverse reactions (regardless of investigator’s causality assessment) reported in greater than or equal to 10% of subjects who received lamivudine tablets (HBV) and reported at a rate greater than in subjects who received placebo are listed in Table 2. Table 2. Clinical Adverse Reactions a Reported in Greater than or Equal to 10% of Subjects Who Received Lamivudine Tablets (HBV) for 52 to 68 Weeks and at an Incidence Greater than Placebo (Trials 1 to 3) Adverse Event Lamivudine Tablets (HBV) (n = 332) P lacebo ( n = 200) Ear, Nose, and Throat Ear, nose, and throat infections 25% 21% Sore throat 13% 8% G astrointestinal Diarrhea 14% 12% a Includes adverse events regardless of severity and causality assessment. Specified laboratory abnormalities reported in subjects who received lamivudine tablets (HBV) and reported at a rate greater than in subjects who received placebo are listed in Table 3. Table 3. Frequencies of Specified Laboratory Abnormalities Reported during Treatment at a Greater Frequency in Subjects Treated with Lamivudine Tablets (HBV) than with Placebo (Trials 1 to 3) a Test (A bnormal Level) Subjects with Abnormality/ Subjects with Observations Lamivudine Tablets (HBV) P lacebo Serum Lipase ≥2.5 x ULN b 10% 7% Creatine Phosphokinase (CPK) ≥7 x baseline 9% 5% Platelets <50,000/mm 3 4% 3% a Includes subjects treated for 52 to 68 weeks. b Includes observations during and after treatment in the 2 placebo-controlled trials that collected this information. ULN = Upper limit of normal. In subjects followed for up to 16 weeks after discontinuation of treatment, posttreatment ALT elevations were observed more frequently in subjects who had received lamivudine tablets (HBV) than in subjects who had received placebo. A comparison of ALT elevations between Weeks 52 and 68 in subjects who discontinued lamivudine tablets (HBV) at Week 52 and subjects in the same trials who received placebo throughout the treatment course is shown in Table 4. Table 4. Posttreatment ALT Elevations with No-Active-Treatment Follow-up (Trials 1 and 3) A bnormal Value Subjects with ALT Elevation/ Subjects with Observations a Lamivudine Tablets (HBV) b P lacebo b ALT ≥2 x baseline value 27% 19% ALT ≥3 x baseline value c 21% 8% ALT ≥2 x baseline value and absolute ALT >500 IU/L 15% 7% ALT ≥2 x baseline value; and bilirubin >2 x ULN and ≥2 x baseline value 0.7% 0.9% a Each subject may be represented in one or more category. b During treatment phase. c Comparable to a Grade 3 toxicity in accordance with modified WHO criteria. ULN = Upper limit of normal. Clinical Trials Experience in Pediatric Subjects with Chronic HBV Infection Most commonly observed adverse reactions in the pediatric trials were similar to those in adult trials. Posttreatment transaminase elevations were observed in some subjects followed after cessation of lamivudine tablets (HBV).

6.2 Postmarketing Experience The following adverse reactions have been identified during post-approval use of lamivudine tablets (HBV). Because these reactions are reported voluntarily from a population of unknown size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. These reactions have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to lamivudine. Blood and Lymph atic Anemia (including pure red cell aplasia and severe anemias progressing on therapy), lymphadenopathy, splenomegaly, thrombocytopenia. Digestive Stomatitis. Endocrine and Metabolic Hyperglycemia. General Weakness. Hepatic and Pancreatic Lactic acidosis and steatosis [see Warnings and Precautions (5.4) ], posttreatment exacerbations of hepatitis [see Warnings and Precautions (5.1) ], pancreatitis. Hypersensitivity Anaphylaxis, urticaria. Musculoskeletal Cramps, rhabdomyolysis. Nervous Paresthesia, peripheral neuropathy. Respiratory Abnormal breath sounds/wheezing. Skin Alopecia, pruritus, rash.

Sorbitol: Coadministration of lamivudine and sorbitol may result in decreased lamivudine concentrations; when possible, avoid chronic coadministration. Consider more frequent monitoring of HBV viral load when chronic coadministration cannot be avoided. (7.2)

7.1 Drugs Inhibiting Organic Cation Transporters Lamivudine is predominantly eliminated in the urine by active organic cationic secretion. The possibility of interactions with other drugs administered concurrently should be considered, particularly when their main route of elimination is active renal secretion via the organic cationic transport system (e.g., trimethoprim) [see Clinical Pharmacology (12.3)]. No data are available regarding interactions with other drugs that have renal clearance mechanisms similar to that of lamivudine.

7.2 Sorbitol Coadministration of single doses of lamivudine and sorbitol resulted in a sorbitol dose-dependent reduction in lamivudine exposures. When possible, avoid use of sorbitol-containing medicines with lamivudine [see Clinical Pharmacology (12.3]. Consider more frequent monitoring of HBV viral load when chronic coadministration cannot be avoided.

8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to lamivudine during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1-800-258-4263. Risk Summary Available data from the APR show no substantial difference in the risk of overall major birth defects for lamivudine compared with the background rate for major birth defects of 2.7% reported in the U.S. reference population of the Metropolitan Atlanta Congenital Defects Program (MACDP). The APR uses the MACDP as a U.S. reference population for birth defects in the general population. The MACDP evaluates women and infants from a limited geographic area and does not include outcomes for births that occur at less than 20 weeks’ gestation. Of over 12,900 women exposed to lamivudine in the APR, less than 2% were HBV mono-infected. The majority of women exposed to lamivudine in the APR were HIV-1-infected and were treated with higher doses of lamivudine compared with HBV mono-infected women. In addition to lamivudine, HIV-1-infected women were also treated with other concomitant medications for HIV-1 infection (see Data) . The estimated rate of miscarriage for women exposed to lamivudine in the indicated population is unknown. The estimated background rate of miscarriage in clinically recognized pregnancies in the U.S. general population is 15% to 20%. Oral administration of lamivudine to pregnant rabbits during organogenesis resulted in embryolethality at systemic exposure (AUC) similar to the recommended clinical dose; however, no adverse developmental effects were observed with oral administration of lamivudine to pregnant rats during organogenesis at plasma concentrations (C max ) 60 times the recommended clinical dose (see Data) . Data Human Data : Based on prospective reports from the APR of over 12,900 exposures to lamivudine during pregnancy resulting in live births (including over 5,400 exposed in the first trimester and over 7,500 exposed in the second/third trimester), there was no difference between the overall risk of birth defects with lamivudine compared with the background birth defect rate of 2.7% observed in the U.S. reference population of the MACDP. The prevalence of birth defects in live births was 3.1% (95% CI: 2.7% to 3.6%) following first trimester exposure to lamivudine-containing regimens and 2.9% (95% CI: 2.5% to 3.3%) following second/third trimester exposure to lamivudine-containing regimens. The pharmacokinetics of lamivudine in patients with HBV or HIV-1 infection and in healthy volunteers are similar at similar doses. Lamivudine pharmacokinetics were studied in pregnant women with HIV-1 infection during 2 clinical trials conducted in South Africa. The trials assessed pharmacokinetics in 16 women at 36 weeks’ gestation using 150 mg lamivudine twice daily (3 times the recommended daily dosage for HBV) with zidovudine, 10 women at 38 weeks’ gestation using 150 mg lamivudine twice daily (3 times the recommended daily dosage for HBV) with zidovudine, and 10 women at 38 weeks’ gestation using lamivudine 300 mg twice daily (6 times the recommended daily dosage for HBV) without other antiretrovirals. Lamivudine concentrations were generally similar in maternal, neonatal, and umbilical cord serum samples. In a subset of subjects, amniotic fluid specimens were collected following natural rupture of membranes and confirmed that lamivudine crosses the placenta in humans. Based on limited data at delivery, median (range) amniotic fluid concentrations of lamivudine were 3.9- (1.2- to 12.8-) fold greater compared with paired maternal serum concentrations (n = 8). Animal Data : Lamivudine was administered orally to pregnant rats (at 90, 600, and 4,000 mg per kg per day) and rabbits (at 90, 300, and 1,000 mg per kg per day and at 15, 40, and 90 mg per kg per day) during organogenesis (on Gestation Days 7 through 16 [rat] and 8 through 20 [rabbit]). No evidence of fetal malformations due to lamivudine was observed in rats and rabbits at doses producing plasma concentrations (C max ) approximately 53 or more times higher than human exposure at the recommended daily dose. Evidence of early embryolethality in the absence of maternal toxicity was seen in the rabbit at systemic exposures (AUC) similar to those observed in humans, but there was no indication of this effect in the rat at plasma concentrations (C max ) 60 times higher than human exposure at the recommended daily dose. Studies in pregnant rats showed that lamivudine is transferred to the fetus through the placenta. In the fertility/pre-and postnatal development study in rats, lamivudine was administered orally at doses of 180, 900, and 4,000 mg per kg per day (from prior to mating through postnatal Day 20). In the study, development of the offspring, including fertility and reproductive performance, was not affected by maternal administration of lamivudine at plasma concentrations (C max ) 104 times higher than human exposure.

8.2 Lactation Risk Summary Lamivudine is present in human milk. There is no information available regarding lamivudine concentrations in milk from lactating women receiving lamivudine for treatment of HBV infection. However, in lactating women with HIV-1 infection being treated with lamivudine at 3 or 6 times the recommended daily dose for HBV, lamivudine concentrations in milk were similar to those observed in serum ( see Data). The lamivudine dose received by a breastfed infant of a mother being treated for HIV-1 infection was estimated to be approximately 6% of the recommended daily lamivudine dose for HBV in children over 2 years of age. There is no information available regarding the effects of the drug on the breastfed infant or on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for lamivudine tablets (HBV) and any potential adverse effects on the breastfed infant from lamivudine or from the underlying maternal condition. Data In mothers with HIV receiving lamivudine monotherapy (300 mg twice daily [6 times the recommended daily dosage for HBV]) or combination therapy (150 mg lamivudine twice daily [3 times the recommended daily dosage for HBV] with 300 mg zidovudine twice daily), the median breast milk to plasma lamivudine concentration ratio was 0.6 to 3.3, and the estimated infant daily dose was approximately 6% of the recommended 3-mg-per-kg daily lamivudine dose for treatment of HBV in children over 2 years of age. In breastfed infants of mothers with HIV-1 infection receiving lamivudine therapy, the blood concentrations of lamivudine decreased after delivery and were undetectable at 6 months despite constant milk concentrations. This is consistent with increased lamivudine renal clearance in the first 6 months of life.

8.4 Pediatric Use Lamivudine tablets (HBV) is indicated for the treatment of chronic hepatitis B virus infection in pediatric patients aged 2 to 17 years [see Indications and Usage ( 1 ), Clinical Pharmacology ( 12.3 ), Clinical Studies ( 14.2 )] . The safety and efficacy of lamivudine tablets (HBV) in pediatric patients younger than 2 years have not been established.

8.5 Geriatric Use Clinical trials of lamivudine tablets (HBV) did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. In general, caution should be exercised in the administration of lamivudine tablets (HBV) in elderly patients reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy [see Dosage and Administration (2.4), Clinical Pharmacology (12.3)]. […]

Lamivudine is an antiviral agent with activity against HBV [see Microbiology ( 12.4 )].