Dosage Form: powder, for oral inhalation
FULL PRESCRIBING INFORMATION
Indications and Usage for Relenza
Treatment of Influenza
Relenza® (zanamivir) Inhalation Powder is indicated for treatment of uncomplicated acute illness due to influenza A and B virus in adults and pediatric patients aged 7 years and older who have been symptomatic for no more than 2 days.
Prophylaxis of Influenza
Relenza is indicated for prophylaxis of influenza in adults and pediatric patients aged 5 years and older.
Important Limitations on Use of Relenza
- Relenza is not recommended for treatment or prophylaxis of influenza in individuals with underlying airways disease (such as asthma or chronic obstructive pulmonary disease) due to risk of serious bronchospasm [see Warnings and Precautions (5.1)].
- Relenza has not been proven effective for treatment of influenza in individuals with underlying airways disease.
- Relenza has not been proven effective for prophylaxis of influenza in the nursing home setting.
- Relenza is not a substitute for early influenza vaccination on an annual basis as recommended by the Centers for Disease Control's Immunization Practices Advisory Committee.
- Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use Relenza.
- There is no evidence for efficacy of zanamivir in any illness caused by agents other than influenza virus A and B.
- Patients should be advised that the use of Relenza for treatment of influenza has not been shown to reduce the risk of transmission of influenza to others.
Relenza Dosage and Administration
Dosing Considerations
- Relenza is for administration to the respiratory tract by oral inhalation only, using the DISKHALER device provided [see Warnings and Precautions (5.6)].
- The 10-mg dose is provided by 2 inhalations (one 5-mg blister per inhalation).
- Patients should be instructed in the use of the delivery system. Instructions should include a demonstration whenever possible. If Relenza is prescribed for children, it should be used only under adult supervision and instruction, and the supervising adult should first be instructed by a healthcare professional [see Patient Counseling Information (17.4)].
- Patients scheduled to use an inhaled bronchodilator at the same time as Relenza should use their bronchodilator before taking Relenza [see Patient Counseling Information (17.2)].
Treatment of Influenza
- The recommended dose of Relenza for treatment of influenza in adults and pediatric patients aged 7 years and older is 10 mg twice daily (approximately 12 hours apart) for 5 days.
- Two doses should be taken on the first day of treatment whenever possible provided there is at least 2 hours between doses.
- On subsequent days, doses should be about 12 hours apart (e.g., morning and evening) at approximately the same time each day.
- The safety and efficacy of repeated treatment courses have not been studied.
Prophylaxis of Influenza
Household Setting:
- The recommended dose of Relenza for prophylaxis of influenza in adults and pediatric patients aged 5 years and older in a household setting is 10 mg once daily for 10 days.
- The dose should be administered at approximately the same time each day.
- There are no data on the effectiveness of prophylaxis with Relenza in a household setting when initiated more than 1.5 days after the onset of signs or symptoms in the index case.
Community Outbreaks:
- The recommended dose of Relenza for prophylaxis of influenza in adults and adolescents in a community setting is 10 mg once daily for 28 days.
- The dose should be administered at approximately the same time each day.
- There are no data on the effectiveness of prophylaxis with Relenza in a community outbreak when initiated more than 5 days after the outbreak was identified in the community.
- The safety and effectiveness of prophylaxis with Relenza have not been evaluated for longer than 28 days’ duration.
Dosage Forms and Strengths
Blister for oral inhalation: 5 mg. Four 5-mg blisters of powder on a ROTADISK for oral inhalation via DISKHALER. Packaged in carton containing 5 ROTADISKs (total of 10 doses) and 1 DISKHALER inhalation device [see How Supplied/Storage and Handling (16)].
Contraindications
Do not use in patients with history of allergic reaction to any ingredient of Relenza including milk proteins [see Warnings and Precautions (5.2), Description (11)].
Warnings and Precautions
Bronchospasm
Relenza is not recommended for treatment or prophylaxis of influenza in individuals with underlying airways disease (such as asthma or chronic obstructive pulmonary disease).
Serious cases of bronchospasm, including fatalities, have been reported during treatment with Relenza in patients with and without underlying airways disease. Many of these cases were reported during postmarketing and causality was difficult to assess.
Relenza should be discontinued in any patient who develops bronchospasm or decline in respiratory function; immediate treatment and hospitalization may be required.
Some patients without prior pulmonary disease may also have respiratory abnormalities from acute respiratory infection that could resemble adverse drug reactions or increase patient vulnerability to adverse drug reactions.
Bronchospasm was documented following administration of zanamivir in 1 of 13 patients with mild or moderate asthma (but without acute influenza-like illness) in a Phase I study. In a Phase III study in patients with acute influenza-like illness superimposed on underlying asthma or chronic obstructive pulmonary disease, 10% (24 of 244) of patients on zanamivir and 9% (22 of 237) on placebo experienced a greater than 20% decline in FEV1 following treatment for 5 days.
If use of Relenza is considered for a patient with underlying airways disease, the potential risks and benefits should be carefully weighed. If a decision is made to prescribe Relenza for such a patient, this should be done only under conditions of careful monitoring of respiratory function, close observation, and appropriate supportive care including availability of fast-acting bronchodilators.
Allergic Reactions
Allergic-like reactions, including oropharyngeal edema, serious skin rashes, and anaphylaxis have been reported in postmarketing experience with Relenza. Relenza should be stopped and appropriate treatment instituted if an allergic reaction occurs or is suspected.
Neuropsychiatric Events
Influenza can be associated with a variety of neurologic and behavioral symptoms which can include events such as seizures, hallucinations, delirium, and abnormal behavior, in some cases resulting in fatal outcomes. These events may occur in the setting of encephalitis or encephalopathy but can occur without obvious severe disease.
There have been postmarketing reports (mostly from Japan) of delirium and abnormal behavior leading to injury in patients with influenza who were receiving neuraminidase inhibitors, including Relenza. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made, but they appear to be uncommon based on usage data for Relenza. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of Relenza to these events has not been established. Patients with influenza should be closely monitored for signs of abnormal behavior. If neuropsychiatric symptoms occur, the risks and benefits of continuing treatment should be evaluated for each patient.
Limitations of Populations Studied
Safety and efficacy have not been demonstrated in patients with high-risk underlying medical conditions. No information is available regarding treatment of influenza in patients with any medical condition sufficiently severe or unstable to be considered at imminent risk of requiring inpatient management.
Bacterial Infections
Serious bacterial infections may begin with influenza-like symptoms or may coexist with or occur as complications during the course of influenza. Relenza has not been shown to prevent such complications.
Importance of Proper Route of Administration
Relenza Inhalation Powder must not be made into an extemporaneous solution for administration by nebulization or mechanical ventilation. There have been reports of hospitalized patients with influenza who received a solution made with Relenza Inhalation Powder administered by nebulization or mechanical ventilation, including a fatal case where it was reported that the lactose in this formulation obstructed the proper functioning of the equipment. Relenza Inhalation Powder must only be administered using the device provided [see Dosage and Administration (2.1)].
Importance of Proper Use of DISKHALER
Effective and safe use of Relenza requires proper use of the DISKHALER to inhale the drug. Prescribers should carefully evaluate the ability of young children to use the delivery system if use of Relenza is considered [see Use in Specific Populations (8.4)].
Adverse Reactions
See Warnings and Precautions for information about risk of serious adverse events such as bronchospasm (5.1) and allergic-like reactions (5.2), and for safety information in patients with underlying airways disease (5.1).
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 practice.
The placebo used in clinical studies consisted of inhaled lactose powder, which is also the vehicle for the active drug; therefore, some adverse events occurring at similar frequencies in different treatment groups could be related to lactose vehicle inhalation.
Treatment of Influenza: Clinical Trials in Adults and Adolescents: Adverse events that occurred with an incidence ≥1.5% in treatment studies are listed in Table 1. This table shows adverse events occurring in patients aged ≥12 years receiving Relenza 10 mg inhaled twice daily, Relenza in all inhalation regimens, and placebo inhaled twice daily (where placebo consisted of the same lactose vehicle used in Relenza).
| Adverse Event | Relenza | Placebo (Lactose Vehicle) (n = 1,520) | |
10 mg b.i.d. Inhaled (n = 1,132) | All Dosing Regimensa (n = 2,289) | ||
| Body as a whole | |||
| Headaches | 2% | 2% | 3% |
| Digestive | |||
| Diarrhea | 3% | 3% | 4% |
| Nausea | 3% | 3% | 3% |
| Vomiting | 1% | 1% | 2% |
| Respiratory | |||
| Nasal signs and symptoms | 2% | 3% | 3% |
| Bronchitis | 2% | 2% | 3% |
| Cough | 2% | 2% | 3% |
| Sinusitis | 3% | 2% | 2% |
| Ear, nose, and throat infections | 2% | 1% | 2% |
| Nervous system | |||
| Dizziness | 2% | 1% | <1% |
| a Includes studies where Relenza was administered intranasally (6.4 mg 2 to 4 times per day in addition to inhaled preparation) and/or inhaled more frequently (q.i.d.) than the currently recommended dose. | |||
Additional adverse reactions occurring in less than 1.5% of patients receiving Relenza included malaise, fatigue, fever, abdominal pain, myalgia, arthralgia, and urticaria.
The most frequent laboratory abnormalities in Phase III treatment studies included elevations of liver enzymes and CPK, lymphopenia, and neutropenia. These were reported in similar proportions of zanamivir and lactose vehicle placebo recipients with acute influenza-like illness.
Clinical Trials in Pediatric Patients: Adverse events that occurred with an incidence ≥1.5% in children receiving treatment doses of Relenza in 2 Phase III studies are listed in Table 2. This table shows adverse events occurring in pediatric patients aged 5 to 12 years receiving Relenza 10 mg inhaled twice daily and placebo inhaled twice daily (where placebo consisted of the same lactose vehicle used in Relenza).
| a Includes a subset of patients receiving Relenza for treatment of influenza in a prophylaxis study. | ||
| Adverse Event | Relenza 10 mg b.i.d. Inhaled (n = 291) | Placebo (Lactose Vehicle) (n = 318) |
| Respiratory | ||
| Ear, nose, and throat infections | 5% | 5% |
| Ear, nose, and throat hemorrhage | <1% | 2% |
| Asthma | <1% | 2% |
| Cough | <1% | 2% |
| Digestive | ||
| Vomiting | 2% | 3% |
| Diarrhea | 2% | 2% |
| Nausea | <1% | 2% |
In 1 of the 2 studies described in Table 2, some additional information is available from children (aged 5 to 12 years) without acute influenza-like illness who received an investigational prophylaxis regimen of Relenza; 132 children received Relenza and 145 children received placebo. Among these children, nasal signs and symptoms (zanamivir 20%, placebo 9%), cough (zanamivir 16%, placebo 8%), and throat/tonsil discomfort and pain (zanamivir 11%, placebo 6%) were reported more frequently with Relenza than placebo. In a subset with chronic pulmonary disease, lower respiratory adverse events (described as asthma, cough, or viral respiratory infections which could include influenza-like symptoms) were reported in 7 of 7 zanamivir recipients and 5 of 12 placebo recipients.
Prophylaxis of Influenza: Family/Household Prophylaxis Studies: Adverse events that occurred with an incidence of ≥1.5% in the 2 prophylaxis studies are listed in Table 3. This table shows adverse events occurring in patients aged ≥5 years receiving Relenza 10 mg inhaled once daily for 10 days.
| a In prophylaxis studies, symptoms associated with influenza-like illness were captured as adverse events; subjects were enrolled during a winter respiratory season during which time any symptoms that occurred were captured as adverse events. | ||
| Adverse Event | Contact Cases | |
Relenza (n = 1,068) | Placebo (n = 1,059) | |
| Lower respiratory | ||
| Viral respiratory infections | 13% | 19% |
| Cough | 7% | 9% |
| Neurologic | ||
| Headaches | 13% | 14% |
| Ear, nose, and throat | ||
| Nasal signs and symptoms | 12% | 12% |
| Throat and tonsil discomfort and pain | 8% | 9% |
| Nasal inflammation | 1% | 2% |
| Musculoskeletal | ||
| Muscle pain | 3% | 3% |
| Endocrine and metabolic | ||
| Feeding problems (decreased or increased appetite and anorexia) | 2% | 2% |
| Gastrointestinal | ||
| Nausea and vomiting | 1% | 2% |
| Non-site specific | ||
| Malaise and fatigue | 5% | 5% |
| Temperature regulation disturbances (fever and/or chills) | 5% | 4% |
Community Prophylaxis Studies: Adverse events that occurred with an incidence of ≥1.5% in 2 prophylaxis studies are listed in Table 4. This table shows adverse events occurring in patients aged ≥5 years receiving Relenza 10 mg inhaled once daily for 28 days.
| a In prophylaxis studies, symptoms associated with influenza-like illness were captured as adverse events; subjects were enrolled during a winter respiratory season during which time any symptoms that occurred were captured as adverse events. | ||
| Adverse Event | Relenza (n = 2,231) | Placebo (n = 2,239) |
| Neurologic | ||
| Headaches | 24% | 26% |
| Ear, nose, and throat | ||
| Throat and tonsil discomfort and pain | 19% | 20% |
| Nasal signs and symptoms | 12% | 13% |
| Ear, nose, and throat infections | 2% | 2% |
| Lower respiratory | ||
| Cough | 17% | 18% |
| Viral respiratory infections | 3% | 4% |
| Musculoskeletal | ||
| Muscle pain | 8% | 8% |
| Musculoskeletal pain | 6% | 6% |
| Arthralgia and articular rheumatism | 2% | <1% |
| Endocrine and metabolic | ||
| Feeding problems (decreased or increased appetite and anorexia) | 4% | 4% |
| Gastrointestinal | ||
| Nausea and vomiting | 2% | 3% |
| Diarrhea | 2% | 2% |
| Non-site specific | ||
| Temperature regulation disturbances (fever and/or chills) | 9% | 10% |
| Malaise and fatigue | 8% | 8% |
Postmarketing Experience
In addition to adverse events reported from clinical trials, the following events have been identified during postmarketing use of zanamivir (Relenza). Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to zanamivir (Relenza).
Allergic Reactions: Allergic or allergic-like reaction, including oropharyngeal edema [see Warnings and Precautions (5.2)].
Psychiatric: Delirium, including symptoms such as altered level of consciousness, confusion, abnormal behavior, delusions, hallucinations, agitation, anxiety, nightmares[see Warnings and Precautions (5.3)].
Cardiac: Arrhythmias, syncope.
Neurologic: Seizures. Vasovagal-like episodes have been reported shortly following inhalation of zanamivir.
Respiratory: Bronchospasm, dyspnea [see Warnings and Precautions (5.1)].
Skin: Facial edema; rash, including serious cutaneous reactions (e.g., erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis); urticaria [see Warnings and Precautions (5.2)].
Drug Interactions
Zanamivir is not a substrate nor does it affect cytochrome P450 (CYP) isoenzymes (CYP1A1/2, 2A6, 2C9, 2C18, 2D6, 2E1, and 3A4) in human liver microsomes. No clinically significant pharmacokinetic drug interactions are predicted based on data from in vitro studies.
The concurrent use of Relenza with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of potential interference between these products, LAIV should not be administered within 2 weeks before or 48 hours after administration of Relenza, unless medically indicated. The concern about possible interference arises from the potential for antiviral drugs to inhibit replication of live vaccine virus.
Trivalent inactivated influenza vaccine can be administered at any time relative to use of Relenza [see Clinical Pharmacology (12.4)].
USE IN SPECIFIC POPULATIONS
Pregnancy
Pregnancy Category C. There are no adequate and well-controlled studies of zanamivir in pregnant women. Zanamivir should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Embryo/fetal development studies were conducted in rats (dosed from days 6 to 15 of pregnancy) and rabbits (dosed from days 7 to 19 of pregnancy) using the same IV doses (1, 9, and 90 mg/kg/day). Pre- and post-natal developmental studies were performed in rats (dosed from day 16 of pregnancy until litter day 21 to 23). No malformations, maternal toxicity, or embryotoxicity were observed in pregnant rats or rabbits and their fetuses. Because of insufficient blood sampling timepoints in rat and rabbit reproductive toxicity studies, AUC values were not available. In a subchronic study in rats at the 90 mg/kg/day IV dose, the AUC values were greater than 300 times the human exposure at the proposed clinical dose.
An additional embryo/fetal study, in a different strain of rat, was conducted using subcutaneous administration of zanamivir, 3 times daily, at doses of 1, 9, or 80 mg/kg during days 7 to 17 of pregnancy. There was an increase in the incidence rates of a variety of minor skeleton alterations and variants in the exposed offspring in this study. Based on AUC measurements, the 80 mg/kg dose produced an exposure greater than 1,000 times the human exposure at the proposed clinical dose. However, in most instances, the individual incidence rate of each skeletal alteration or variant remained within the background rates of the historical occurrence in the strain studied.
Zanamivir has been shown to cross the placenta in rats and rabbits. In these animals, fetal blood concentrations of zanamivir were significantly lower than zanamivir concentrations in the maternal blood.
Nursing Mothers
Studies in rats have demonstrated that zanamivir is excreted in milk. However, nursing mothers should be instructed that it is not known whether zanamivir is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Relenza is administered to a nursing mother.
Pediatric Use
Treatment of Influenza: Safety and effectiveness of Relenza for treatment of influenza have not been assessed in pediatric patients younger than 7 years, but were studied in a Phase III treatment study in pediatric patients, where 471 children aged 5 to 12 years received zanamivir or placebo [see Clinical Studies (14.1)]. Adolescents were included in the 3 principal Phase III adult treatment studies. In these studies, 67 patients were aged 12 to 16 years. No definite differences in safety and efficacy were observed between these adolescent patients and young adults.
In a Phase I study of 16 children aged 6 to 12 years with signs and symptoms of respiratory disease, 4 did not produce a measurable peak inspiratory flow rate (PIFR) through the DISKHALER (3 with no adequate inhalation on request, 1 with missing data), 9 had measurable PIFR on each of 2 inhalations, and 3 achieved measurable PIFR on only 1 of 2 inhalations. Neither of two 6-year-olds and one of two 7-year-olds produced measurable PIFR. Overall, 8 of the 16 children (including all those younger than 8 years) either did not produce measurable inspiratory flow through the DISKHALER or produced peak inspiratory flow rates below the 60 L/min considered optimal for the device under standardized in vitro testing; lack of measurable flow rate was related to low or undetectable serum concentrations [see Clinical Pharmacology (12.3), Clinical Studies (14.1)]. Prescribers should carefully evaluate the ability of young children to use the delivery system if prescription of Relenza is considered.
Prophylaxis of Influenza: The safety and effectiveness of Relenza for prophylaxis of influenza have been studied in 4 Phase III studies where 273 children aged 5 to 11 years and 239 adolescents aged 12 to 16 years received Relenza. No differences in safety and effectiveness were observed between pediatric and adult subjects [see Clinical Studies (14.2)].
Geriatric Use
Of the total number of patients in 6 clinical studies of Relenza for treatment of influenza, 59 patients were aged 65 years and older, while 24 patients were aged 75 years and older. Of the total number of patients in 4 clinical studies of Relenza for prophylaxis of influenza in households and community settings, 954 patients were aged 65 years and older, while 347 patients were aged 75 years and older. No overall differences in safety or effectiveness were observed between these patients and younger patients, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out. Elderly patients may need assistance with use of the device.
In 2 additional studies of Relenza for prophylaxis of influenza in the nursing home setting, efficacy was not demonstrated [see Indications and Usage (1.3)].
Overdosage
There have been no reports of overdosage from administration of Relenza.
Relenza Description
The active component of Relenza is zanamivir. The chemical name of zanamivir is 5 - (acetylamino) - 4 - [(aminoiminomethyl) - amino] - 2,6 - anhydro - 3,4,5 - trideoxy - D - glycero - D - galacto - non - 2 - enonic acid. It has a molecular formula of C12H20N4O7 and a molecular weight of 332.3. It has the following structural formula:
Zanamivir is a white to off-white powder for oral inhalation with a solubility of approximately 18 mg/mL in water at 20°C.
Relenza is for administration to the respiratory tract by oral inhalation only. Each Relenza ROTADISK contains 4 regularly spaced double-foil blisters with each blister containing a powder mixture of 5 mg of zanamivir and 20 mg of lactose (which contains milk proteins). The contents of each blister are inhaled using a specially designed breath-activated plastic device for inhaling powder called the DISKHALER. After a Relenza ROTADISK is loaded into the DISKHALER, a blister that contains medication is pierced and the zanamivir is dispersed into the air stream created when the patient inhales through the mouthpiece. The amount of drug delivered to the respiratory tract will depend on patient factors such as inspiratory flow. Under standardized in vitro testing, Relenza ROTADISK delivers 4 mg of zanamivir from the DISKHALER device when tested at a pressure drop of 3 kPa (corresponding to a flow rate of about 62 to 65 L/min) for 3 seconds.
Relenza - Clinical Pharmacology
Mechanism of Action
Zanamivir is an antiviral drug [see Clinical Pharmacology (12.4)].
Pharmacokinetics
Absorption and Bioavailability: Pharmacokinetic studies of orally inhaled zanamivir indicate that approximately 4% to 17% of the inhaled dose is systemically absorbed. The peak serum concentrations ranged from 17 to 142 ng/mL within 1 to 2 hours following a 10 mg dose. The area under the serum concentration versus time curve (AUC∞) ranged from 111 to 1,364 ng•hr/mL.
Distribution: Zanamivir has limited plasma protein binding (<10%).
Metabolism: Zanamivir is renally excreted as unchanged drug. No metabolites have been detected in humans.
Elimination: The serum half-life of zanamivir following administration by oral inhalation ranges from 2.5 to 5.1 hours. It is excreted unchanged in the urine with excretion of a single dose completed within 24 hours. Total clearance ranges from 2.5 to 10.9 L/hr. Unabsorbed drug is excreted in the feces.
Impaired Hepatic Function: The pharmacokinetics of zanamivir have not been studied in patients with impaired hepatic function.
Impaired Renal Function: After a single intravenous dose of 4 mg or 2 mg of zanamivir in volunteers with mild/moderate or severe renal impairment, respectively, significant decreases in renal clearance (and hence total clearance: normals 5.3 L/hr, mild/moderate 2.7 L/hr, and severe 0.8 L/hr; median values) and significant increases in half-life (normals 3.1 hr, mild/moderate 4.7 hr, and severe 18.5 hr; median values) and systemic exposure were observed. Safety and efficacy have not been documented in the presence of severe renal insufficiency. Due to the low systemic bioavailability of zanamivir following oral inhalation, no dosage adjustments are necessary in patients with renal impairment. However, the potential for drug accumulation should be considered.
Pediatric Patients: The pharmacokinetics of zanamivir were evaluated in pediatric patients with signs and symptoms of respiratory illness. Sixteen patients, aged 6 to 12 years, received a single dose of 10 mg zanamivir dry powder via DISKHALER. Five patients had either undetectable zanamivir serum concentrations or had low drug concentrations (8.32 to 10.38 ng/mL) that were not detectable after 1.5 hours. Eleven patients had Cmax median values of 43 ng/mL (range: 15 to 74) and AUC∞ median values of 167 ng•hr/mL (range: 58 to 279). Low or undetectable serum concentrations were related to lack of measurable PIFR in individual patients [see Use in Specific Populations (8.4), Clinical Studies (14.1)].
Geriatric Patients: The pharmacokinetics of zanamivir have not been studied in patients older than 65 years [see Use in Specific Populations (8.5)].
Gender, Race, and Weight: In a population pharmacokinetic analysis in patient studies, no clinically significant differences in serum concentrations and/or pharmacokinetic parameters (V/F, CL/F, ka, AUC0-3, Cmax, Tmax, CLr, and % excreted in urine) were observed when demographic variables (gender, age, race, and weight) and indices of infection (laboratory evidence of infection, overall symptoms, symptoms of upper respiratory illness, and viral titers) were considered. There were no significant correlations between measures of systemic exposure and safety parameters.
Microbiology
Mechanism of Action: Zanamivir is an inhibitor of influenza virus neuraminidase affecting release of viral particles.
Antiviral Activity: The antiviral activity of zanamivir against laboratory and clinical isolates of influenza virus was determined in cell culture assays. The concentrations of zanamivir required for inhibition of influenza virus were highly v
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