Ribavirin

Ribavirin for Inhalation Solution, USP is indicated for the treatment of hospitalized infants and young children with severe lower respiratory tract infections due to RSV. Treatment early in the course of severe lower respiratory tract infection may be necessary to achieve efficacy. Only severe RSV lower respiratory tract infection should be treated with Ribavirin for Inhalation Solution, USP. The vast majority of infants and children with RSV infection have disease that is mild, self-limited, and does not require hospitalization or antiviral treatment. Many children with mild lower respiratory tract involvement will require shorter hospitalization than would be required for a full course of Ribavirin for Inhalation Solution, USP aerosol (3 to 7 days) and should not be treated with the drug. Thus the decision to treat with Ribavirin for Inhalation Solution, USP should be based on the severity of the RSV infection. The presence of an underlying condition such as prematurity, immunosuppression or cardiopulmonary disease may increase the severity of clinical manifestations and complications of RSV infection. Use of aerosolized Ribavirin for Inhalation Solution, USP in patients requiring mechanical ventilator assistance should be undertaken only by physicians and support staff familiar with this mode of administration and the specific ventilator being used (see WARNINGS and DOSAGE AND ADMINISTRATION ). Diagnosis RSV infection should be documented by a rapid diagnostic method such as demonstration of viral antigen in respiratory tract secretions by immunofluorescence 3,4 or ELISA 5 before or during the first 24 hours of treatment. Treatment may be initiated while awaiting rapid diagnostic test results. However, treatment should not be continued without documentation of RSV infection. Non-culture antigen detection techniques may have false positive or false negative results. Assessment of the clinical situation, the time of year and other parameters may warrant reevaluation of the laboratory diagnosis. Description of Studies Non-Mechanically Ventilated Infants: In two placebo-controlled trials in infants hospitalized with RSV lower respiratory tract infection, aerosolized Ribavirin for Inhalation Solution, USP treatment had a therapeutic effect, as judged by the reduction in severity of clinical manifestations of disease by treatment day 3. 3,4 Treatment was most effective when instituted within the first 3 days of clinical illness. Virus titers in respiratory secretions were also significantly reduced with Ribavirin for Inhalation Solution, USP in one of these original studies. 4 Additional controlled studies conducted since these initial trials of aerosolized Ribavirin for Inhalation Solution, USP in the treatment of RSV infection have supported these data. Mechanically Ventilated Infants: A randomized, double-blind, placebo-controlled evaluation of aerosolized Ribavirin for Inhalation Solution, USP at the recommended dose was conducted in 28 infants requiring mechanical ventilation for respiratory failure caused by documented RSV infection. 6 Mean age was 1.4 months (SD, 1.7 months). Seven patients had underlying diseases predisposing them to severe infection and 21 were previously normal. Aerosolized Ribavirin for Inhalation Solution, USP treatment significantly decreased the duration of mechanical ventilation required (4.9 vs. 9.9 days, p=0.01) and duration of required supplemental oxygen (8.7 vs. 13.5 days, p=0.01). Intensive patient management and monitoring techniques were employed in this study. These included endotracheal tube suctioning every 1 to 2 hours; recording of proximal airway pressure, ventilatory rate, and F l O 2 every hour; and arterial blood gas monitoring every 2 to 6 hours. To reduce the risk of Ribavirin for Inhalation Solution, USP precipitation and ventilator malfunction, heated wire tubing, two bacterial filters connected in series in the expiratory limb of the ventilator (with filter changes every 4 hours), and water column pressure release valves to monitor internal ventilator pressures were used in connecting ventilator circuits to the SPAG ® -2. Employing these techniques, no technical difficulties with Ribavirin for Inhalation Solution, USP administration were encountered during the study. Adverse events consisted of bacterial pneumonia in one case, staphylococcus bacteremia in one case and two cases of post-extubation stridor. None were felt to be related to Ribavirin for Inhalation Solution, USP administration.

Ribavirin for Inhalation Solution, USP is contraindicated in individuals who have shown hypersensitivity to the drug or its components, and in women who are or may become pregnant during exposure to the drug. Ribavirin has demonstrated significant teratogenic and/or embryocidal potential in all animal species in which adequate studies have been conducted (rodents and rabbits). Therefore, although clinical studies have not been performed, it should be assumed that Ribavirin for Inhalation Solution, USP may cause fetal harm in humans. Studies in which the drug has been administered systemically demonstrate that ribavirin is concentrated in the red blood cells and persists for the life of the erythrocyte.

SUDDEN DETERIORATION OF RESPIRATORY FUNCTION HAS BEEN ASSOCIATED WITH INITIATION OF AEROSOLIZED RIBAVIRIN FOR INHALATION SOLUTION, USP USE IN INFANTS. Respiratory function should be carefully monitored during treatment. If initiation of aerosolized Ribavirin for Inhalation Solution, USP treatment appears to produce sudden deterioration of respiratory function, treatment should be stopped and reinstituted only with extreme caution, continuous monitoring, and consideration of concomitant administration of bronchodilators. Use with Mechanical Ventilators USE OF AEROSOLIZED RIBAVIRIN FOR INHALATION SOLUTION, USP IN PATIENTS REQUIRING MECHANICAL VENTILATOR ASSISTANCE SHOULD BE UNDERTAKEN ONLY BY PHYSICIANS AND SUPPORT STAFF FAMILIAR WITH THIS MODE OF ADMINISTRATION AND THE SPECIFIC VENTILATOR BEING USED. Strict attention must be paid to procedures that have been shown to minimize the accumulation of drug precipitate, which can result in mechanical ventilator dysfunction and associated increased pulmonary pressures. These procedures include the use of bacteria filters in series in the expiratory limb of the ventilator circuit with frequent changes (every 4 hours), water column pressure release valves to indicate elevated ventilator pressures, frequent monitoring of these devices and verification that ribavirin crystals have not accumulated within the ventilator circuitry, and frequent suctioning and monitoring of the patient (see Description of Studies). Those administering aerosolized Ribavirin for Inhalation Solution, USP in conjunction with mechanical ventilator use should be thoroughly familiar with detailed descriptions of these procedures as outlined in the SPAG-2 Instructions for Use.

General Patients with severe lower respiratory tract infection due to RSV require optimum monitoring and attention to respiratory and fluid status (see SPAG-2 Instructions for Use). Drug Interactions Clinical studies of interactions of Ribavirin for Inhalation Solution, USP with other drugs commonly used to treat infants with RSV infections, such as digoxin, bronchodilators, other antiviral agents, antibiotics or anti-metabolites, have not been conducted. Interference by Ribavirin for Inhalation Solution, USP with laboratory tests has not been evaluated. Carcinogenesis and Mutagenesis Ribavirin increased the incidence of cell transformations and mutations in mouse Balb/c 3T3 (fibroblasts) and L5178Y (lymphoma) cells at concentrations of 0.015 and 0.03-5.0 mg/mL, respectively (without metabolic activation). Modest increases in mutation rates (3-4x) were observed at concentrations between 3.75-10.0 mg/mL in L5178Y cells in vitro with the addition of a metabolic activation fraction. In the mouse micronucleus assay, ribavirin was clastogenic at intravenous doses of 20-200 mg/kg, (estimated human equivalent of 1.67-16.7 mg/kg, based on body surface area adjustment for a 60 kg adult). Ribavirin was not mutagenic in a dominant lethal assay in rats at intraperitoneal doses between 50-200 mg/kg when administered for 5 days (estimated human equivalent of 7.14-28.6 mg/kg, based on body surface area adjustment; see Pharmacokinetics ). In vivo carcinogenicity studies with ribavirin are incomplete. However, results of a chronic feeding study with ribavirin in rats, at doses of 16-100 mg/kg/day (estimated human equivalent of 2.3-14.3 mg/kg/day, based on body surface area adjustment for the adult), suggest that ribavirin may induce benign mammary, pancreatic, pituitary and adrenal tumors. Preliminary results of two oral gavage oncogenicity studies in the mouse and rat (18-24 months; doses of 20-75 and 10-40 mg/kg/day, respectively [estimated human equivalent of 1.67-6.25 and 1.43-5.71 mg/kg/day, respectively, based on body surface area adjustment for the adult]) are inconclusive as to the carcinogenic potential of ribavirin (see Pharmacokinetics ). However, these studies have demonstrated a relationship between chronic ribavirin exposure and increased incidences of vascular lesions (microscopic hemorrhages in mice) and retinal degeneration (in rats). Impairment of Fertility The fertility of ribavirin-treated animals (male or female) has not been fully investigated. However, in the mouse, administration of ribavirin at doses between 35-150 mg/kg/day (estimated human equivalent of 2.92-12.5 mg/kg/day, based on body surface area adjustment for the adult) resulted in significant seminiferous tubule atrophy, decreased sperm concentrations, and increased numbers of sperm with abnormal morphology. Partial recovery of sperm production was apparent 3-6 months following dose cessation. In several additional toxicology studies, ribavirin has been shown to cause testicular lesions (tubular atrophy) in adult rats at oral dose levels as low as 16 mg/kg/day (estimated human equivalent of 2.29 mg/kg/day, based on body surface area adjustment; see Pharmacokinetics ). Lower doses were not tested. The reproductive capacity of treated male animals has not been studied. Ribavirin has demonstrated significant teratogenic and/or embryocidal potential in all animal species in which adequate studies have been conducted. Teratogenic effects were evident after single oral doses of 2.5 mg/kg or greater in the hamster, and after daily oral doses of 0.3 and 1.0 mg/kg in the rabbit and rat, respectively (estimated human equivalent doses of 0.12 and 0.14 mg/kg, based on body surface area adjustment for the adult). Malformations of the skull, palate, eye, jaw, limbs, skeleton, and gastrointestinal tract were noted. The incidence and severity of teratogenic effects increased with escalation of the drug dose. Survival of fetuses and offspring was reduced. Ribavirin caused embryolethality in the rabbit at daily oral dose levels as low as 1 mg/kg. No teratogenic effects were evident in the rabbit and rat administered daily oral doses of 0.1 and 0.3 mg/kg, respectively with estimated human equivalent doses of 0.01 and 0.04 mg/kg, based on body surface area adjustment (see Pharmacokinetics ). These doses are considered to define the No Observable Teratogenic Effects Level (NOTEL) for ribavirin in the rabbit and rat. Following oral administration of ribavirin in the pregnant rat (1.0 mg/kg) and rabbit (0.3 mg/kg), mean plasma levels of drug ranged from 0.10-0.20 µ M [0.024-0.049 µ /mL] at 1 hour after dosing, to undetectable levels at 24 hours. At 1 hour following the administration of 0.3 or 0.1 mg/kg in the rat and rabbit (NOTEL), respectively, mean plasma levels of drug in both species were near or below the limit of detection (0.05 µ M; see Pharmacokinetics ). Although clinical studies have not been performed, Ribavirin for Inhalation Solution, USP may cause fetal harm in humans. As noted previously, ribavirin is concentrated in red blood cells and persists for the life of the cell. Thus the terminal half-life for the systemic elimination of ribavirin is essentially that of the half-life of circulating erythrocytes. The minimum interval following exposure to Ribavirin for Inhalation Solution, USP before pregnancy may be safely initiated is unknown (see CONTRAINDICATIONS , WARNINGS , and Information for Health Care Personnel ). Lactation Ribavirin for Inhalation Solution, USP has been shown to be toxic to lactating animals and their offspring. It is not known if Ribavirin for Inhalation Solution, USP is excreted in human milk. Information for Health Care Personnel Health care workers directly providing care to patients receiving aerosolized Ribavirin for Inhalation Solution, USP should be aware that ribavirin has been shown to be teratogenic in all animal species in which adequate studies have been conducted (rodents and rabbits). Although no reports of teratogenesis in offspring of mothers who were exposed to aerosolized Ribavirin for Inhalation Solution, USP during pregnancy have been confirmed, no controlled studies have been conducted in pregnant women. Studies of environmental exposure in treatment settings have shown that the drug can disperse into the immediate bedside area during routine patient care activities with highest ambient levels closest to the patient and extremely low levels outside of the immediate bedside area. Adverse reactions resulting from actual occupational exposure in adults are described below (see Adverse Events in Health Care Workers ). Some studies have documented ambient drug concentrations at the bedside that could potentially lead to systemic exposures above those considered safe for exposure during pregnancy (1/1000 of the NOTEL dose in the most sensitive animal species). 7, 8, 9 A 1992 study conducted by the National Institute of Occupational Safety and Health (NIOSH) demonstrated measurable urine levels of ribavirin in health care workers exposed to aerosol in the course of direct patient care. 7 Levels were lowest in workers caring for infants receiving aerosolized Ribavirin for Inhalation Solution, USP with mechanical ventilation and highest in those caring for patients being administered the drug via an oxygen tent or hood. This study employed a more sensitive assay to evaluate ribavirin levels in urine than was available for several previous studies of environmental exposure that failed to detect measurable ribavirin levels in exposed workers. Creatinine adjusted urine levels in the NIOSH study ranged from less than 0.001 to 0.140 µ M of ribavirin per gram of creatinine in exposed workers. However, the relationship between urinary ribavirin levels in exposed workers, plasma levels in animal studies, and the specific risk of teratogenesis in exposed pregnant women is unknown. […]

The description of adverse reactions is based on events from clinical studies (approximately 200 patients) conducted prior to 1986, and the controlled trial of aerosolized Ribavirin for Inhalation Solution, USP conducted in 1989-1990. Additional data from spontaneous post-marketing reports of adverse events in individual patients have been available since 1986. Deaths Deaths during or shortly after treatment with aerosolized Ribavirin for Inhalation Solution, USP have been reported in 20 cases of patients treated with Ribavirin for Inhalation Solution, USP (12 of these patients were being treated for RSV infections). Several cases have been characterized as “possibly related” to Ribavirin for Inhalation Solution, USP by the treating physician; these were in infants who experienced worsening respiratory status related to bronchospasm while being treated with the drug. Several other cases have been attributed to mechanical ventilator malfunction in which Ribavirin for Inhalation Solution, USP precipitation within the ventilator apparatus led to excessively high pulmonary pressures and diminished oxygenation. In these cases the monitoring procedures described in the current package insert were not employed (see Description of Studies , WARNINGS , and DOSAGE AND ADMINISTRATION ). Pulmonary and Cardiovascular Pulmonary function significantly deteriorated during aerosolized Ribavirin for Inhalation Solution, USP treatment in six of six adults with chronic obstructive lung disease and in four of six asthmatic adults. Dyspnea and chest soreness were also reported in the latter group. Minor abnormalities in pulmonary function were also seen in healthy adult volunteers. In the original study population of approximately 200 infants who received aerosolized Ribavirin for Inhalation Solution, USP, several serious adverse events occurred in severely ill infants with life-threatening underlying diseases, many of whom required assisted ventilation. The role of Ribavirin for Inhalation Solution, USP in these events is indeterminate. Since the drug’s approval in 1986, additional reports of similar serious, though non-fatal, events have been filed infrequently. Events associated with aerosolized Ribavirin for Inhalation Solution, USP use have included the following: Pulmonary: Worsening of respiratory status, bronchospasm, pulmonary edema, hypoventilation, cyanosis, dyspnea, bacterial pneumonia, pneumothorax, apnea, atelectasis and ventilator dependence. Cardiovascular: Cardiac arrest, hypotension, bradycardia and digitalis toxicity. Bigeminy, bradycardia and tachycardia have been described in patients with underlying congenital heart disease. Some subjects requiring assisted ventilation experienced serious difficulties, due to inadequate ventilation and gas exchange. Precipitation of drug within the ventilatory apparatus, including the endotracheal tube, has resulted in increased positive end expiratory pressure and increased positive inspiratory pressure. Accumulation of fluid in tubing (“rain out”) has also been noted. Measures to avoid these complications should be followed carefully (see DOSAGE AND ADMINISTRATION ). Hematologic Although anemia was not reported with use of aerosolized Ribavirin for Inhalation Solution, USP in controlled clinical trials, most infants treated with the aerosol have not been evaluated 1 to 2 weeks post-treatment when anemia is likely to occur. Anemia has been shown to occur frequently with experimental oral and intravenous Ribavirin for Inhalation Solution, USP in humans. Also, cases of anemia (type unspecified), reticulocytosis and hemolytic anemia associated with aerosolized Ribavirin for Inhalation Solution, USP use have been reported through post-marketing reporting systems. All have been reversible with discontinuation of the drug. Other Rash and conjunctivitis have been associated with the use of aerosolized Ribavirin for Inhalation Solution, USP. These usually resolve within hours of discontinuing therapy. Seizures and asthenia associated with experimental intravenous Ribavirin for Inhalation Solution, USP therapy have also been reported. Adverse Events in Health Care Workers Studies of environmental exposure to aerosolized Ribavirin for Inhalation Solution, USP in health care workers administering care to patients receiving the drug have not detected adverse signs or symptoms related to exposure. However, 152 health care workers have reported experiencing adverse events through post-marketing surveillance. Nearly all were in individuals providing direct care to infants receiving aerosolized Ribavirin for Inhalation Solution, USP. Of 358 events from these 152 individual health care worker reports, the most common signs and symptoms were headache (51% of reports), conjunctivitis (32%), and rhinitis, nausea, rash, dizziness, pharyngitis, or lacrimation (10-20% each). Several cases of bronchospasm and/or chest pain were also reported, usually in individuals with known underlying reactive airway disease. Several case reports of damage to contact lenses after prolonged close exposure to aerosolized Ribavirin for Inhalation Solution, USP have also been reported. Most signs and symptoms reported as having occurred in exposed health care workers resolved within minutes to hours of discontinuing close exposure to aerosolized Ribavirin for Inhalation Solution, USP (also see Information for Health Care Personnel ). The symptoms of RSV in adults can include headache, conjunctivitis, sore throat and/or cough, fever, hoarseness, nasal congestion and wheezing, although RSV infections in adults are typically mild and transient. Such infections represent a potential hazard to uninfected hospital patients. It is unknown whether certain symptoms cited in reports from health care workers were due to exposure to the drug or infection with RSV. Hospitals should implement appropriate infection control procedures. To report SUSPECTED ADVERSE REACTIONS, contact Oceanside Pharmaceuticals at 1-800-321-4576 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Clinical studies of interactions of Ribavirin for Inhalation Solution, USP with other drugs commonly used to treat infants with RSV infections, such as digoxin, bronchodilators, other antiviral agents, antibiotics or anti-metabolites, have not been conducted. Interference by Ribavirin for Inhalation Solution, USP with laboratory tests has not been evaluated.

Ribavirin has demonstrated significant teratogenic and/or embryocidal potential in all animal species in which adequate studies have been conducted. Teratogenic effects were evident after single oral doses of 2.5 mg/kg or greater in the hamster, and after daily oral doses of 0.3 and 1.0 mg/kg in the rabbit and rat, respectively (estimated human equivalent doses of 0.12 and 0.14 mg/kg, based on body surface area adjustment for the adult). Malformations of the skull, palate, eye, jaw, limbs, skeleton, and gastrointestinal tract were noted. The incidence and severity of teratogenic effects increased with escalation of the drug dose. Survival of fetuses and offspring was reduced. Ribavirin caused embryolethality in the rabbit at daily oral dose levels as low as 1 mg/kg. No teratogenic effects were evident in the rabbit and rat administered daily oral doses of 0.1 and 0.3 mg/kg, respectively with estimated human equivalent doses of 0.01 and 0.04 mg/kg, based on body surface area adjustment (see Pharmacokinetics ). These doses are considered to define the No Observable Teratogenic Effects Level (NOTEL) for ribavirin in the rabbit and rat. Following oral administration of ribavirin in the pregnant rat (1.0 mg/kg) and rabbit (0.3 mg/kg), mean plasma levels of drug ranged from 0.10-0.20 µ M [0.024-0.049 µ /mL] at 1 hour after dosing, to undetectable levels at 24 hours. At 1 hour following the administration of 0.3 or 0.1 mg/kg in the rat and rabbit (NOTEL), respectively, mean plasma levels of drug in both species were near or below the limit of detection (0.05 µ M; see Pharmacokinetics ). Although clinical studies have not been performed, Ribavirin for Inhalation Solution, USP may cause fetal harm in humans. As noted previously, ribavirin is concentrated in red blood cells and persists for the life of the cell. Thus the terminal half-life for the systemic elimination of ribavirin is essentially that of the half-life of circulating erythrocytes. The minimum interval following exposure to Ribavirin for Inhalation Solution, USP before pregnancy may be safely initiated is unknown (see CONTRAINDICATIONS , WARNINGS , and Information for Health Care Personnel ).

Ribavirin for Inhalation Solution, USP has been shown to be toxic to lactating animals and their offspring. It is not known if Ribavirin for Inhalation Solution, USP is excreted in human milk.

In cell cultures the inhibitory activity of ribavirin for respiratory syncytial virus (RSV) is selective. The mechanism of action is unknown. Reversal of the in vitro antiviral activity by guanosine or xanthosine suggests ribavirin may act as an analogue of these cellular metabolites. Microbiology Ribavirin has demonstrated antiviral activity against RSV in vitro 1 and in experimentally infected cotton rats. 2 Several clinical isolates of RSV were evaluated for ribavirin susceptibility by plaque reduction in tissue culture. Plaques were reduced 85-98% by 16 mcg/mL; however, results may vary with the test system. The development of resistance has not been evaluated in vitro or in clinical trials. In addition to the above, ribavirin has been shown to have in vitro activity against influenza A and B viruses and herpes simplex virus, but the clinical significance of these data is unknown. Immunologic Effects Neutralizing antibody responses to RSV were decreased in aerosolized Ribavirin for Inhalation Solution, USP-treated infants compared to placebo-treated infants. 3 One study also showed that RSV-specific IgE antibody in bronchial secretions was decreased in patients treated with aerosolized Ribavirin for Inhalation Solution, USP. In rats, ribavirin administration resulted in lymphoid atrophy of the thymus, spleen and lymph nodes. Humoral immunity was reduced in guinea pigs and ferrets. Cellular immunity was also mildly depressed in animal studies. The clinical significance of these observations is unknown.