178 Treatment and Prophylaxis

Amantadine: adverse reactions to amantadine have only rarely been observed among patients with liver disease.

Seizure Disorders

Seizures (or seizure-like activity) have rarely been reported among patients with a history of seizures who were not receiving anticonvulsant medication while taking amantadine or rimantadine.

Pregnancy

All drugs mentioned above should only be used during pregnancy if the potential benefit justifies the potential risk to the foetus (Pregnancy Category C).

Treatment of Human H5N1 Influenza

Experience with the treatment of H5N1 disease in humans is limited – until 8 March 2006, 175 confirmed cases had been reported to the WHO (WHO 2006), and clinical reports published to date include only a few patients (Yuen 1998, Chan 2002, Hien 2004, Chotpitayasunondh 2005, WHO 2005, de Jong 2005).

Based on current data, the treatment of influenza disease caused by the currently circulating H5N1 strains might be somewhat different from the treatment of “classical” influenza (WHO 2006b). However, it should be noted that current recommendations are preliminary and modifications are likely as new data come in:

•Patients with suspected H5N1 influenza should promptly receive a neuraminidase inhibitor pending the results of laboratory testing (WHO 2005).

•Oseltamivir (Tamiflu®) is currently regarded as the drug of choice.

•Consider increasing the dose of oseltamivir in severe disease (150 mg twice daily in adults) and continue treatment for longer periods (7–10 days or longer) (WHO 2005, WHO 2006b).

•Resistance may occur and precede clinical deterioration (de Jong 2005).

•Treatment with oseltamivir may be beneficial even when initiated as late as 8 days after the onset of symptoms, if there is evidence of ongoing viral replication (WHO 2005, de Jong 2005).

Corticosteroids have frequently been used, with conflicting results. In one series, six of the seven patients who were treated with corticosteroids died (Hien 2004). Ribavirin, interferon alpha and other immunomodulatory drugs have all been used, but without convincing results.

In severe cases, ventilatory support and intensive care may be needed within days of admission (Hien 2004, Chotpitayasunondh 2005).