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英文药名: Zerit(Stavudine Capsules/Oral Solution) 中文药名: 赛瑞特（司他夫定胶囊/口服液） 生产厂家: 施贵宝公司
2.4 Method of Preparation for Oral Solution Dispense solution in original container with measuring cup provided. Instruct patient to shake the container vigorously prior to measuring each dose and to store the tightly closed container in a refrigerator, 2°C to 8°C (36°F to 46°F). Discard any unused portion after 30 days. 3 DOSAGE FORMS AND STRENGTHS • ZERIT 15 mg capsules with dark red cap and light yellow body, printed with black ink “BMS 1964” on the cap and with black ink “15” on the body. • ZERIT 20 mg capsules with light brown cap and light brown body, printed with black ink “BMS 1965” on the cap and with black ink “20” on the body. • ZERIT 30 mg capsules with dark orange cap and light orange body, printed with black ink “BMS 1966” on the cap and with black ink “30” on the body. • ZERIT 40 mg capsules with dark orange cap and dark orange body, printed with black ink “BMS 1967” on the cap and with black ink “40” on the body. • ZERIT for oral solution is a dye-free, fruit-flavored powder that provides 1 mg of stavudine per milliliter solution after constitution. 4 CONTRAINDICATIONS ZERIT is contraindicated in patients with clinically significant hypersensitivity to stavudine or to any of the components contained in the formulation. 5 WARNINGS AND PRECAUTIONS 5.1 Lactic Acidosis/Severe Hepatomegaly with Steatosis Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues alone or in combination, including stavudine and other antiretrovirals. Although relative rates of lactic acidosis have not been assessed in prospective well-controlled trials, longitudinal cohort and retrospective studies suggest that this infrequent event may be more often associated with antiretroviral combinations containing stavudine. Female gender, obesity, and prolonged nucleoside exposure may be risk factors. Fatal lactic acidosis has been reported in pregnant women who received the combination of stavudine and didanosine with other antiretroviral agents. The combination of stavudine and didanosine should be used with caution during pregnancy and is recommended only if the potential benefit clearly outweighs the potential risk [see Use in Specific Populations (8.1)]. Particular caution should be exercised when administering ZERIT to any patient with known risk factors for liver disease; however, cases of lactic acidosis have also been reported in patients with no known risk factors. Generalized fatigue, digestive symptoms (nausea, vomiting, abdominal pain, and unexplained weight loss); respiratory symptoms (tachypnea and dyspnea); or neurologic symptoms, including motor weakness [see Warnings and Precautions (5.3)] might be indicative of the development of symptomatic hyperlactatemia or lactic acidosis syndrome. Treatment with ZERIT (stavudine) should be suspended in any patient who develops clinical or laboratory findings suggestive of symptomatic hyperlactatemia, lactic acidosis, or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations). Permanent discontinuation of ZERIT should be considered for patients with confirmed lactic acidosis. 5.2 Hepatic Toxicity The safety and efficacy of ZERIT have not been established in HIV-infected patients with significant underlying liver disease. During combination antiretroviral therapy, patients with preexisting liver dysfunction, including chronic active hepatitis, have an increased frequency of liver function abnormalities, including severe and potentially fatal hepatic adverse events, and should be monitored according to standard practice. If there is evidence of worsening liver disease in such patients, interruption or discontinuation of treatment must be considered. Hepatotoxicity and hepatic failure resulting in death were reported during postmarketing surveillance in HIV-infected patients treated with hydroxyurea and other antiretroviral agents. Fatal hepatic events were reported most often in patients treated with the combination of hydroxyurea, didanosine, and stavudine. This combination should be avoided. [See Adverse Reactions (6).] Use with Interferon and Ribavirin-Based Regimens In vitro studies have shown ribavirin can reduce the phosphorylation of pyrimidine nucleoside analogues such as stavudine. Although no evidence of a pharmacokinetic or pharmacodynamic (eg, loss of HIV-1/HCV virologic suppression) interaction was seen when ribavirin was coadministered with stavudine in HIV-1/HCV co-infected patients [see Drug Interactions (7)], hepatic decompensation (some fatal) has occurred in HIV-1/HCV co-infected patients receiving combination antiretroviral therapy for HIV-1 and interferon and ribavirin. Patients receiving interferon with or without ribavirin and stavudine should be closely monitored for treatment-associated toxicities, especially hepatic decompensation. Discontinuation of stavudine should be considered as medically appropriate. Dose reduction or discontinuation of interferon, ribavirin, or both should also be considered if worsening clinical toxicities are observed, including hepatic decompensation (eg, Child-Pugh >6) (see the full prescribing information for interferon and ribavirin). 5.3 Neurologic Symptoms Motor weakness has been reported rarely in patients receiving combination antiretroviral therapy including ZERIT. Most of these cases occurred in the setting of lactic acidosis. The evolution of motor weakness may mimic the clinical presentation of Guillain-Barré syndrome (including respiratory failure). If motor weakness develops, ZERIT should be discontinued. Symptoms may continue or worsen following discontinuation of therapy. Peripheral sensory neuropathy, manifested by numbness, tingling, or pain in the hands or feet, has been reported in patients receiving ZERIT therapy. Peripheral neuropathy, which can be severe, is dose related and occurs more frequently in patients with advanced HIV-1 disease, a history of peripheral neuropathy, or in patients receiving other drugs that have been associated with neuropathy, including didanosine [see Adverse Reactions (6)]. Patients should be monitored for the development of peripheral neuropathy. Stavudine-related peripheral neuropathy may resolve if therapy is withdrawn promptly. If peripheral neuropathy develops permanent discontinuation of ZERIT should be considered. In some cases, symptoms may worsen temporarily following discontinuation of therapy. 5.4 Pancreatitis Fatal and nonfatal pancreatitis have occurred during therapy when ZERIT was part of a combination regimen that included didanosine in both treatment-naive and treatment-experienced patients, regardless of degree of immunosuppression. The combination of ZERIT and didanosine and any other agents that are toxic to the pancreas should be suspended in patients with suspected pancreatitis. Reinstitution of ZERIT after a confirmed diagnosis of pancreatitis should be undertaken with particular caution and close patient monitoring; avoid use in combination with didanosine. 5.5 Fat Redistribution Redistribution/accumulation of body fat including central obesity, dorsocervical fat enlargement (buffalo hump), peripheral wasting, facial wasting, breast enlargement, and “cushingoid appearance” have been observed in patients receiving antiretroviral therapy. In randomized controlled trials of treatment-naive patients, clinical lipoatrophy or lipodystrophy developed in a higher proportion of patients treated with stavudine compared to other nucleosides (tenofovir or abacavir). Dual energy x-ray absorptiometry (DEXA) scans demonstrated overall limb fat loss in stavudine-treated patients compared to limb fat gain or no gain in patients treated with other nucleosides (abacavir, tenofovir, or zidovudine). The incidence and severity of lipoatrophy or lipodystrophy are cumulative over time with stavudine-containing regimens. In clinical trials, switching from stavudine to other nucleosides (tenofovir or abacavir) resulted in increases in limb fat with modest to no improvements in clinical lipoatrophy. Patients receiving ZERIT should be monitored for symptoms or signs of lipoatrophy or lipodystrophy and questioned about body changes related to lipoatrophy or lipodystrophy. Given the potential risks of using ZERIT including lipoatrophy or lipodystrophy, a benefit-risk assessment for each patient should be made and an alternative antiretroviral should be considered. 5.6 Immune Reconstitution Syndrome Immune reconstitution syndrome has been reported in patients treated with combination antiretroviral therapy, including ZERIT. During the initial phase of combination antiretroviral treatment, patients whose immune system responds may develop an inflammatory response to indolent or residual opportunistic infections (such as Mycobacterium avium infection, cytomegalovirus, Pneumocystis jiroveci pneumonia (PCP), or tuberculosis), which may necessitate further evaluation and treatment. Autoimmune disorders (such as Graves’ disease, polymyositis, and Guillain-Barré syndrome) have also been reported to occur in the setting of immune reconstitution; however, the time to onset is more variable, and can occur many months after initiation of treatment. 6 ADVERSE REACTIONS The following adverse reactions are discussed in greater detail in other sections of the labeling: • lactic acidosis and severe hepatomegaly with steatosis [see Boxed Warning and Warnings and Precautions (5.1)] • hepatic toxicity [see Warnings and Precautions (5.2)] • neurologic symptoms and motor weakness [see Warnings and Precautions (5.3)] • pancreatitis [see Boxed Warning and Warnings and Precautions (5.4)] • lipoatrophy/lipodystrophy [see Warnings and Precautions (5.5)] When ZERIT is used in combination with other agents with similar toxicities, the incidence of adverse reactions may be higher than when stavudine is used alone. 6.1 Clinical Trial Experience in Adults Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. Selected adverse reactions that occurred in adult patients receiving ZERIT in a controlled monotherapy study (Study AI455-019) are provided in Table 2. Table 2: Selected Adverse Reactions in Study AI455-019a (Monotherapy)
Selected adverse reactions that occurred in antiretroviral-naive adult patients receiving ZERIT from two controlled combination studies are provided in Table 3. Table 3: Selected Adverse Reactionsa in START 1 and START 2b Studies (Combination Therapy)
Table 4: Selected Laboratory Abnormalities in Study AI455-019a,b
Table 5: Selected Laboratory Abnormalities in START 1 and START 2 Studies (Grades 3–4)
Adverse reactions and serious laboratory abnormalities reported in pediatric patients from birth through adolescence during clinical trials were similar in type and frequency to those seen in adult patients. [See Use in Specific Populations (8.4).] 6.3 Postmarketing Experience The following adverse reactions have been identified during postmarketing use of ZERIT. 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 their seriousness, frequency of reporting, causal connection to ZERIT, or a combination of these factors. Body as a Whole: abdominal pain, allergic reaction, chills/fever, and redistribution/accumulation of body fat [see Warnings and Precautions (5.5)]. Digestive Disorders: anorexia. Exocrine Gland Disorders: pancreatitis, including fatal cases [see Warnings and Precautions (5.4)]. Hematologic Disorders: anemia, leukopenia, thrombocytopenia, neutropenia, and macrocytosis. Liver: symptomatic hyperlactatemia/lactic acidosis and hepatic steatosis [see Warnings and Precautions (5.1)], hepatitis and liver failure. Metabolic Disorders: lipoatrophy, lipodystrophy [see Warnings and Precautions (5.5)], diabetes mellitus and hyperglycemia. Musculoskeletal: myalgia. Nervous System: insomnia, severe motor weakness (most often reported in the setting of lactic acidosis) [see Warnings and Precautions (5.1, 5.3)]. Use with Didanosine- and Hydroxyurea-Based Regimens When stavudine is used in combination with other agents with similar toxicities, the incidence of these toxicities may be higher than when stavudine is used alone. Thus, patients treated with ZERIT in combination with didanosine, with or without hydroxyurea, may be at increased risk for pancreatitis and hepatotoxicity, which may be fatal, and severe peripheral neuropathy [see Warnings and Precautions (5)]. The combination of ZERIT and hydroxyurea, with or without didanosine, should be avoided. 7 DRUG INTERACTIONS ZERIT is unlikely to interact with drugs metabolized by cytochrome P450 isoenzymes. Zidovudine: Zidovudine competitively inhibits the intracellular phosphorylation of stavudine. Therefore, use of zidovudine in combination with ZERIT (stavudine) should be avoided. Doxorubicin: In vitro data indicate that the phosphorylation of stavudine is inhibited at relevant concentrations by doxorubicin. The clinical significance of this interaction is unknown; therefore, concomitant use of stavudine with doxorubicin should be undertaken with caution. Ribavirin: In vitro data indicate ribavirin reduces phosphorylation of lamivudine, stavudine, and zidovudine. The clinical significance of the interaction with stavudine is unknown; therefore, concomitant use of stavudine with ribavirin should be undertaken with caution. No pharmacokinetic (eg, plasma concentrations or intracellular triphosphorylated active metabolite concentrations) or pharmacodynamic (eg, loss of HIV-1/HCV virologic suppression) interaction was observed when ribavirin and lamivudine (n=18), stavudine (n=10), or zidovudine (n=6) were coadministered as part of a multi-drug regimen to HIV-1/HCV co-infected patients [see Warnings and Precautions (5.2)]. 8 USE IN SPECIFIC POPULATIONS 8.1 Pregnancy Pregnancy Category C Reproduction studies have been performed in rats and rabbits with exposures (based on Cmax) up to 399 and 183 times, respectively, of that seen at a clinical dosage of 1 mg/kg/day and have revealed no evidence of teratogenicity. The incidence in fetuses of a common skeletal variation, unossified or incomplete ossification of sternebra, was increased in rats at 399 times human exposure, while no effect was observed at 216 times human exposure. A slight post-implantation loss was noted at 216 times the human exposure with no effect noted at approximately 135 times the human exposure. An increase in early rat neonatal mortality (birth to 4 days of age) occurred at 399 times the human exposure, while survival of neonates was unaffected at approximately 135 times the human exposure. A study in rats showed that stavudine is transferred to the fetus through the placenta. The concentration in fetal tissue was approximately one-half the concentration in maternal plasma. Animal reproduction studies are not always predictive of human response. There are no adequate and well-controlled studies of stavudine in pregnant women. Stavudine should be used during pregnancy only if the potential benefit justifies the potential risk. Fatal lactic acidosis has been reported in pregnant women who received the combination of stavudine and didanosine with other antiretroviral agents. It is unclear if pregnancy augments the risk of lactic acidosis/hepatic steatosis syndrome reported in nonpregnant individuals receiving nucleoside analogues [see Boxed Warning and Warnings and Precautions (5.1)]. The combination of stavudine and didanosine should be used with caution during pregnancy and is recommended only if the potential benefit clearly outweighs the potential risk. Healthcare providers caring for HIV-infected pregnant women receiving stavudine should be alert for early diagnosis of lactic acidosis/hepatic steatosis syndrome. Antiretroviral Pregnancy Registry: To monitor maternal-fetal outcomes of pregnant women exposed to stavudine and other antiretroviral agents, an Antiretroviral Pregnancy Registry has been established. Physicians are encouraged to register patients by calling 1-800-258-4263. 8.3 Nursing Mothers The Centers for Disease Control and Prevention recommend that HIV-infected mothers not breastfeed their infants to avoid risking postnatal transmission of HIV. Studies in lactating rats demonstrated that stavudine is excreted in milk. Although it is not known whether stavudine is excreted in human milk, there exists the potential for adverse effects from stavudine in nursing infants. Because of both the potential for HIV transmission and the potential for serious adverse reactions in nursing infants, mothers should be instructed not to breastfeed if they are receiving ZERIT. 8.4 Pediatric Use Use of stavudine in pediatric patients from birth through adolescence is supported by evidence from adequate and well-controlled studies of stavudine in adults with additional pharmacokinetic and safety data in pediatric patients [see Dosage and Administration (2.2) and Adverse Reactions (6.2)]. Adverse reactions and laboratory abnormalities reported to occur in pediatric patients in clinical studies were generally consistent with the safety profile of stavudine in adults. These studies include ACTG 240, where 105 pediatric patients ages 3 months to 6 years received ZERIT 2 mg/kg/day for a median of 6.4 months; a controlled clinical trial where 185 newborns received ZERIT 2 mg/kg/day either alone or in combination with didanosine from birth through 6 weeks of age; and a clinical trial where 8 newborns received ZERIT 2 mg/kg/day in combination with didanosine and nelfinavir from birth through 4 weeks of age. Stavudine pharmacokinetics have been evaluated in 25 HIV-1-infected pediatric patients ranging in age from 5 weeks to 15 years and in weight from 2 to 43 kg after IV or oral administration of single doses and twice-daily regimens and in 30 HIV-1-exposed or -infected newborns ranging in age from birth to 4 weeks after oral administration of twice-daily regimens [see Clinical Pharmacology (12.3, Table 9)]. 8.5 Geriatric Use Clinical studies of ZERIT (stavudine) did not include sufficient numbers of patients aged 65 years and over to determine whether they respond differently than younger patients. Greater sensitivity of some older individuals to the effects of ZERIT cannot be ruled out. In a monotherapy Expanded Access Program for patients with advanced HIV-1 infection, peripheral neuropathy or peripheral neuropathic symptoms were observed in 15 of 40 (38%) elderly patients receiving 40 mg twice daily and 8 of 51 (16%) elderly patients receiving 20 mg twice daily. Of the approximately 12,000 patients enrolled in the Expanded Access Program, peripheral neuropathy or peripheral neuropathic symptoms developed in 30% of patients receiving 40 mg twice daily and 25% of patients receiving 20 mg twice daily. Elderly patients should be closely monitored for signs and symptoms of peripheral neuropathy. ZERIT is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, it may be useful to monitor renal function. Dose adjustment is recommended for patients with renal impairment [see Dosage and Administration (2.3)]. 8.6 Renal Impairment Data from two studies in adults indicated that the apparent oral clearance of stavudine decreased and the terminal elimination half-life increased as creatinine clearance decreased. Based on these observations, it is recommended that the ZERIT dosage be modified in patients with reduced creatinine clearance and in patients receiving maintenance hemodialysis [see Dosage and Administration (2.3) and Clinical Pharmacology (12.3)]. 10 OVERDOSAGE Experience with adults treated with 12 to 24 times the recommended daily dosage revealed no acute toxicity. Complications of chronic overdosage include peripheral neuropathy and hepatic toxicity. Stavudine can be removed by hemodialysis; the mean ± SD hemodialysis clearance of stavudine is 120 ± 18 mL/min. Whether stavudine is eliminated by peritoneal dialysis has not been studied. 11 DESCRIPTION ZERIT® is the brand name for stavudine (d4T), a synthetic thymidine nucleoside analogue, active against the human immunodeficiency virus type 1 (HIV-1). The chemical name for stavudine is 2′,3′-didehydro-3′-deoxythymidine. Stavudine has the following structural formula: Stavudine is a white to off-white crystalline solid with the molecular formula C10H12N2O4 and a molecular weight of 224.2. The solubility of stavudine at 23°C is approximately 83 mg/mL in water and 30 mg/mL in propylene glycol. The n-octanol/water partition coefficient of stavudine at 23°C is 0.144. Capsules: ZERIT is available as capsules for oral administration containing either 15, 20, 30, or 40 mg of stavudine. Each capsule also contains inactive ingredients microcrystalline cellulose, sodium starch glycolate, lactose, and magnesium stearate. The hard gelatin shell consists of gelatin, titanium dioxide, and iron oxides. The capsules are printed with edible inks. Powder for Oral Solution: ZERIT is available as a dye-free, fruit-flavored powder in bottles with child-resistant closures providing 200 mL of a 1 mg/mL stavudine oral solution upon constitution with water per label instructions. The powder for oral solution contains the following inactive ingredients: methylparaben, propylparaben, sodium carboxymethylcellulose, sucrose, and antifoaming and flavoring agents. 12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Stavudine is an antiviral drug [see Clinical Pharmacology (12.4)]. 12.3 Pharmacokinetics The pharmacokinetics of stavudine have been evaluated in HIV-1-infected adult and pediatric patients (Tables 7, 8, and 9). Peak plasma concentrations (Cmax) and area under the plasma concentration-time curve (AUC) increased in proportion to dose after both single and multiple doses ranging from 0.03 to 4 mg/kg. There was no significant accumulation of stavudine with repeated administration every 6, 8, or 12 hours. Absorption Following oral administration, stavudine is rapidly absorbed, with peak plasma concentrations occurring within 1 hour after dosing. The systemic exposure to stavudine is the same following administration as capsules or solution. Steady-state pharmacokinetic parameters of ZERIT (stavudine) in HIV-1-infected adults are shown in Table 7. Table 7: Steady-State Pharmacokinetic Parameters of ZERIT in HIV-1-Infected Adults
Binding of stavudine to serum proteins was negligible over the concentration range of 0.01 to 11.4 µg/mL. Stavudine distributes equally between red blood cells and plasma. Volume of distribution is shown in Table 8. Metabolism Metabolism plays a limited role in the clearance of stavudine. Unchanged stavudine was the major drug-related component circulating in plasma after an 80-mg dose of 14C-stavudine, while metabolites constituted minor components of the circulating radioactivity. Minor metabolites include oxidized stavudine, glucuronide conjugates of stavudine and its oxidized metabolite, and an N-acetylcysteine conjugate of the ribose after glycosidic cleavage, suggesting that thymine is also a metabolite of stavudine. Elimination Following an 80-mg dose of 14C-stavudine to healthy subjects, approximately 95% and 3% of the total radioactivity was recovered in urine and feces, respectively. Radioactivity due to parent drug in urine and feces was 73.7% and 62.0%, respectively. The mean terminal elimination half-life is approximately 2.3 hours following single oral doses. Mean renal clearance of the parent compound is approximately 272 mL/min, accounting for approximately 67% of the apparent oral clearance. In HIV-1-infected patients, renal elimination of unchanged drug accounts for about 40% of the overall clearance regardless of the route of administration (Table 8). The mean renal clearance was about twice the average endogenous creatinine clearance, indicating active tubular secretion in addition to glomerular filtration. Table 8: Pharmacokinetic Parameters of Stavudine in HIV-1-Infected Adults: Bioavailability, Distribution, and Clearance
Pediatric Pharmacokinetic parameters of stavudine in pediatric patients are presented in Table 9. Table 9: Pharmacokinetic Parameters (Mean ± SD) of Stavudine in HIV-1-Exposed or -Infected Pediatric Patients
Data from two studies in adults indicated that the apparent oral clearance of stavudine decreased and the terminal elimination half-life increased as creatinine clearance decreased (see Table 10). Cmax and Tmax were not significantly altered by renal impairment. The mean ± SD hemodialysis clearance value of stavudine was 120 ± 18 mL/min (n=12); the mean ± SD percentage of the stavudine dose recovered in the dialysate, timed to occur between 2–6 hours post-dose, was 31 ± 5%. Based on these observations, it is recommended that ZERIT (stavudine) dosage be modified in patients with reduced creatinine clearance and in patients receiving maintenance hemodialysis [see Dosage and Administration (2.3)]. Table 10: Mean ± SD Pharmacokinetic Parameter Values of ZERITa in Adults with Varying Degrees of Renal Function
Stavudine pharmacokinetics were not altered in five non-HIV-infected patients with hepatic impairment secondary to cirrhosis (Child-Pugh classification B or C) following the administration of a single 40-mg dose. Geriatric Stavudine pharmacokinetics have not been studied in patients >65 years of age. [See Use in Specific Populations (8.5).] Gender A population pharmacokinetic analysis of data collected during a controlled clinical study in HIV-1-infected patients showed no clinically important differences between males (n=291) and females (n=27). Race A population pharmacokinetic analysis of data collected during a controlled clinical study in HIV-1-infected patients showed no clinically important differences between races (n=233 Caucasian, 39 African-American, 41 Hispanic, 1 Asian, and 4 other). Drug Interaction Studies Stavudine does not inhibit the major cytochrome P450 isoforms CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4; therefore, it is unlikely that clinically significant drug interactions will occur with drugs metabolized through these pathways. Because stavudine is not protein-bound, it is not expected to affect the pharmacokinetics of protein-bound drugs. Tables 11 and 12 summarize the effects on AUC and Cmax, with a 95% confidence interval (CI) when available, following coadministration of ZERIT with didanosine, lamivudine, and nelfinavir. No clinically significant pharmacokinetic interactions were observed. Table 11: Results of Drug Interaction Studies with ZERIT: Effects of Coadministered Drug on Stavudine Plasma AUC and Cmax Values
a HIV-1-infected patients 12.4 Microbiology Mechanism of Action Stavudine, a nucleoside analogue of thymidine, is phosphorylated by cellular kinases to the active metabolite stavudine triphosphate. Stavudine triphosphate inhibits the activity of HIV-1 reverse transcriptase (RT) by competing with the natural substrate thymidine triphosphate (Ki=0.0083 to 0.032 µM) and by causing DNA chain termination following its incorporation into viral DNA. Stavudine triphosphate inhibits cellular DNA polymerases β and γ and markedly reduces the synthesis of mitochondrial DNA. Antiviral Activity in Cell Culture The cell culture antiviral activity of stavudine was measured in peripheral blood mononuclear cells, monocytic cells, and lymphoblastoid cell lines. The concentration of drug necessary to inhibit HIV-1 replication by 50% (EC50) ranged from 0.009 to 4 µM against laboratory and clinical isolates of HIV-1. In cell culture, stavudine exhibited additive to antagonistic activity in combination with zidovudine. Stavudine in combination with either abacavir, didanosine, tenofovir, or zalcitabine exhibited additive to synergistic anti-HIV-1 activity. Ribavirin, at the 9–45 µM concentrations tested, reduced the anti-HIV-1 activity of stavudine by 2.5- to 5-fold. The relationship between cell culture susceptibility of HIV-1 to stavudine and the inhibition of HIV-1 replication in humans has not been established. Resistance HIV-1 isolates with reduced susceptibility to stavudine have been selected in cell culture (strain-specific) and were also obtained from patients treated with stavudine. Phenotypic analysis of HIV-1 isolates from 61 patients receiving prolonged (6–29 months) stavudine monotherapy showed that post-therapy isolates from four patients exhibited EC50 values more than 4-fold (range 7- to 16-fold) higher than the average pretreatment susceptibility of baseline isolates. Of these, HIV-1 isolates from one patient contained the zidovudine-resistance-associated substitutions T215Y and K219E, and isolates from another patient contained the multiple-nucleoside-resistance-associated substitution Q151M. Mutations in the RT gene of HIV-1 isolates from the other two patients were not detected. The genetic basis for stavudine susceptibility changes has not been identified. Cross-resistance Cross-resistance among HIV-1 reverse transcriptase inhibitors has been observed. Several studies have demonstrated that prolonged stavudine treatment can select and/or maintain thymidine analogue mutations (TAMs; M41L, D67N, K70R, L210W, T215Y/F, K219Q/E) associated with zidovudine resistance. HIV-1 isolates with one or more TAMs exhibited reduced susceptibility to stavudine in cell culture. These TAMs are seen at a similar frequency with stavudine and zidovudine in virological treatment. The clinical relevance of these findings suggests that stavudine should be avoided in the presence of thymidine analogue mutations. 13 NONCLINICAL TOXICOLOGY 13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility In 2-year carcinogenicity studies in mice and rats, stavudine was noncarcinogenic at doses which produced exposures (AUC) 39 and 168 times, respectively, human exposure at the recommended clinical dose. Benign and malignant liver tumors in mice and rats and malignant urinary bladder tumors in male rats occurred at levels of exposure 250 (mice) and 732 (rats) times human exposure at the recommended clinical dose. Stavudine was not mutagenic in the Ames, E. coli reverse mutation, or the CHO/HGPRT mammalian cell forward gene mutation assays, with and without metabolic activation. Stavudine produced positive results in the in vitro human lymphocyte clastogenesis and mouse fibroblast assays, and in the in vivo mouse micronucleus test. In the in vitro assays, stavudine elevated the frequency of chromosome aberrations in human lymphocytes (concentrations of 25 to 250 µg/mL, without metabolic activation) and increased the frequency of transformed foci in mouse fibroblast cells (concentrations of 25 to 2500 µg/mL, with and without metabolic activation). In the in vivo micronucleus assay, stavudine was clastogenic in bone marrow cells following oral stavudine administration to mice at dosages of 600 to 2000 mg/kg/day for 3 days. No evidence of impaired fertility was seen in rats with exposures (based on Cmax) up to 216 times that observed following a clinical dosage of 1 mg/kg/day. 14 CLINICAL STUDIES Combination Therapy The combination use of ZERIT is based on the results of clinical studies in HIV-1-infected patients in double- and triple-combination regimens with other antiretroviral agents. One of these studies (START 1) was a multicenter, randomized, open-label study comparing ZERIT (40 mg twice daily) plus lamivudine plus indinavir to zidovudine plus lamivudine plus indinavir in 202 treatment-naive patients. Both regimens resulted in a similar magnitude of inhibition of HIV-1 RNA levels and increases in CD4+ cell counts through 48 weeks. Monotherapy The efficacy of ZERIT was demonstrated in a randomized, double-blind study (AI455-019, conducted 1992–1994) comparing ZERIT with zidovudine in 822 patients with a spectrum of HIV-1-related symptoms. The outcome in terms of progression of HIV-1 disease and death was similar for both drugs. 16 HOW SUPPLIED/STORAGE AND HANDLING 16.1 Capsules Table 13: Capsule Strength/Configuration
ZERIT® (stavudine) for Oral Solution is a dye-free, fruit-flavored powder that provides 1 mg of stavudine per mL of solution upon constitution with water. Directions for solution preparation are included on the product label and in the Dosage and Administration (2) section of this insert. ZERIT for Oral Solution (NDC No. 0003-1968-01) is available in child-resistant containers that provide 200 mL of solution after constitution with water. 16.3 Storage ZERIT Capsules should be stored in tightly closed containers at 25°C (77°F). Excursions between 15°C and 30°C (59°F and 86°F) are permitted (see USP Controlled Room Temperature). ZERIT for Oral Solution should be protected from excessive moisture and stored in tightly closed containers at 25°C (77°F). Excursions between 15°C and 30°C (59°F and 86°F) are permitted (see USP Controlled Room Temperature). After constitution, store tightly closed containers of ZERIT for Oral Solution in a refrigerator, 2°C to 8°C (36°F to 46°F). Discard any unused portion after 30 days. 17 PATIENT COUNSELING INFORMATION See MEDICATION GUIDE. 17.1 General Patients should be advised that ZERIT is not a cure for HIV-1 infection, and that they may continue to experience illnesses associated with HIV-1 infection, including opportunistic infections. Patients should be advised to remain under the care of a physician when using ZERIT and the importance of adherence to any antiretroviral regimen including those that contain ZERIT. Patients should be advised to avoid doing things that can spread HIV-1 infection to others. • Do not share needles or other injection equipment. • Do not share personal items that can have blood or body fluids on them, like toothbrushes and razor blades. • Do not have any kind of sex without protection. Always practice safe sex by using a latex or polyurethane condom to lower the chance of sexual contact with semen, vaginal secretions, or blood. • Do not breastfeed. It is not known if ZERIT can be passed to your baby in your breast milk and whether it could harm your baby. Also, mothers with HIV-1 should not breastfeed because HIV-1 can be passed to the baby in breast milk. Patients should be informed that when ZERIT is used in combination with other agents with similar toxicities, the incidence of adverse reactions may be higher than when ZERIT is used alone. Patients should be instructed that if they miss a dose, to take it as soon as possible. If it is almost time for the next dose, skip the missed dose and continue the regular dosing schedule. Patients should be instructed if they take too much ZERIT, they should contact a poison control center or emergency room right away. Patients should be informed that the Centers for Disease Control and Prevention (CDC) recommend that HIV-infected mothers not nurse newborn infants to reduce the risk of postnatal transmission of HIV infection. Patients with diabetes should be aware that ZERIT for Oral Solution contains 50 mg of sucrose (sugar) per mL. 17.2 Lactic Acidosis Patients should be informed of the importance of early recognition of symptoms of symptomatic hyperlactatemia or lactic acidosis syndrome, which include unexplained weight loss, abdominal discomfort, nausea, vomiting, fatigue, dyspnea, and motor weakness. Patients in whom these symptoms develop should seek medical attention immediately. Discontinuation of ZERIT therapy may be required. 17.3 Hepatic Toxicity Patients should be informed that an increased risk of hepatotoxicity, which may be fatal, may occur in patients treated with ZERIT in combination with didanosine and hydroxyurea. This combination should be avoided. 17.4 Peripheral Neuropathy Patients should be informed that an important toxicity of ZERIT (stavudine) is peripheral neuropathy. Patients should be aware that peripheral neuropathy is manifested by numbness, tingling, or pain in hands or feet, and that these symptoms should be reported to their physicians. Patients should be counseled that peripheral neuropathy occurs with greatest frequency in patients who have advanced HIV-1 disease or a history of peripheral neuropathy, and discontinuation of ZERIT may be required if toxicity develops. Caregivers of young children receiving ZERIT therapy should be instructed regarding detection and reporting of peripheral neuropathy. 17.5 Pancreatitis Patients should be informed that an increased risk of pancreatitis, which may be fatal, may occur in patients treated with the combination of ZERIT and didanosine. This combination should be avoided. Patients should be closely monitored for symptoms of pancreatitis. The patient should be instructed to avoid alcohol while taking ZERIT. Alcohol may increase the patient’s risk of pancreatitis or liver damage. 17.6 Fat Redistribution Patients should be informed that redistribution or accumulation of body fat may occur in individuals receiving antiretroviral therapy including ZERIT. Patients receiving ZERIT should be monitored for clinical signs and symptoms of lipoatrophy/lipodystrophy. Patients should be routinely questioned about body changes related to lipoatrophy/lipodystrophy. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
