Synagis, A New Weapon to do Battle with an Old Enemy
by Phillip A. Noe, MSN, PNP, Pediatric Pulmonology

With the changing of the seasons and the approach of winter, pediatric health care workers everywhere are keenly aware of the approach of RSV. RSV or Respiratory Syncytial Virus is a paramyxovirus. It is present in epidemic proportions each year, typically during the fall and winter months. RSV is the most common cause of lower respiratory tract infections in infant and children worldwide. It is responsible for approximately 90,000 hospitalizations annually in the U.S. alone. Infants and children that are at highest risk for developing a particularly severe illness include: those born prematurely, those with a chronic lung disease such as BPD, infants with certain forms of heart disease, or those who are immunocompromised.

For years, the treatment for active illness has been primarily supportive care focusing on adequate ventilation, and hydration; with essentially no effective way to prevent an individual from contacting this illness except isolation. In February 1996, the FDA approved Respigam™ for the prevention of RSV. Respigam is a gamma globulin product that has been used fairly successfully for the past two winters. It has had several disadvantages including:

·         it is a blood product and an immunoglobulin

·         it requires I.V. administration and takes several hours to administer

·         it interferes with live vaccine administration (thus vaccinations must be temporarily delayed).

This past summer, the FDA approved a new product for the treatment of RSV, Synagis™. Synagis or palivizumab is a monoclonal antibody against RSV that is produced by a recombinant DNA. In controlled studies, it has been shown to be as effective against RSV as Respigam with several advantages:

·         it is administered intramuscularly

·         it does not interfere with routine vaccinations

·         it is not a blood product.

The indications for the use of Synagis are very similar to the former indications for Respigam. The formal American Academy of Pediatrics recommendation can be found in the November 1998 issue of Pediatrics. To paraphrase their recommendations, they felt that Synagis should be considered for the following situations:

1.      Infants and children younger than 2 years with severe chronic lung disease that have required recent medical therapy

2.    Infants born at 29 to 32 weeks gestation that are less than 6 months of age at the start of RSV season (which is October)

3.    Infants born at less than 28 weeks gestation that are less than 1 year of age at the start of RSV season

4.    Infants born at 32 to 35 with additional risk factors should be considered on a case by case basis

Finally, infants with uncorrected cyanotic heart disease should probably not receive Synagis. Healthcare workers should review the formal guidelines prior to administering this product, especially with infants and children with congenital heart disease (CHD).

The Committee on Infectious Diseases and Committee on Fetus and Newborn of the American Academy of Pediatrics notes "Palizumab and RSV-IGIV are not licensed by the FDA for patients with CHD. Available data indicates that RSV-IGIV is contraindicated in patients with cyanotic CHD. However, patients with CLD, who are premature, or both, who meet the criteria in the recommendations above and who also have asymptomatic acyanotic CHD (eg, patent ductus arteriosus or ventricular septal defect) may benefit from prophylaxis"¹.

How To Use

Synagis comes in a unit dose vial that contains 100 mg (1 cc) when reconstituted. It is reconstituted by adding 1 ml of sterile water. The mixture is then gently swirled for 30 seconds. Vigorous shaking should be avoided. After reconstituting, the vial should sit at room temperature for 20 minutes before using and should then be administered within 6 hours of reconstituting. The standard dose is 15 mg / kg with the medication being given intramuscularly in the anterolateral thigh. If the dose is greater than 1 cc, the dose should be divided between both legs. Once administered, protective levels of the Antibody against RSV are present in the blood stream in about 24 hours and remain for approximately 30 days. For the best protection, Synagis should be administered on a monthly basis from October through March, for a total of 6 injections.

The recent introduction of Synagis gives pediatric health care workers a fairly effective treatment to protect high risk infants from developing a lower respiratory tract infection due to RSV. Synagis is also less expensive overall when compared to Respigam with the savings due to the ability to provide this medication on an outpatient basis as well as a marked decrease in administration cost. However, it is still a very expensive preventative medication with the average cost for a 1 ml vial being approximately $925 and a winters worth of therapy ranging from $6,000 to $12,000 compared to Respigam at $15,000 to $30,000 per winter. Careful selection of the appropriate candidate is important to maximize this medications effectiveness in preventing serious illness in a cost effective manner.

References

1. Committee on Infectious Diseases and Committee on Fetus and Newborn. American Academy of Pediatrics: Prevention of Respiratory Syncytial Virus Infections: Indications for the Use of Palivizumab and Update on the Use of RSV-IGIV. Pediatrics Vol. 102 No. 5 November 1998, pp. 1211-1216. Abstract

Respigam Respiratory Syncytial Virus Immune Globulin Intravenous (Human) package insert

Synagis (palivizumab) package insert

Glossary

CLD

Chronic Lung Disease, formerly known as bronchopulmonary dysplasia.