When Drugs Stop Working HIV Dr Despair

Antivirals to treat HIV infection need to be carefully combined to maximize effectiveness. (Themba Hadebe/Associated Press)

The antiviral drug Telzir should not be used together with some drugs to treat irregular heartbeat or another specific anti-viral medication used to treat HIV infection, Health Canada warns.

Telzir or fosamprenavir calcium is used in combination with other antivirals to treat HIV infection in adults and children age six and older.

"Telzir should not be used with the antiarrhythmic drugs amiodarone, lidocaine (systemic), or quinidine, as this may cause serious and/or life-threatening reactions such as abnormal heart rhythm (arrhythmias)," Health Canada said Wednesday in a safety update.

In addition, Telzir should not be used with delavirdine, another antiviral drug to treat HIV, because it may reduce the effectiveness of delavirdine. 

The product labels have been updated to better reflect the recommendations.

Health Canada said people should not stop treatment without consulting their doctor or health-care professional.