NHS Greater Glasgow & Clyde Area Drug and Therapeutics Committee
Greater Glasgow and Clyde Medicines
Medicines Update

Posaconazole formulations not interchangeable

Posaconazole (Noxafil®) is a broad-spectrum triazole antifungal It is on the Formulary for specialist use only. Use for the prophylaxis of invasive fungal infections in immunocompromised patients is restricted to patients in whom there is a specific risk of aspergillus infection or where fluconazole or itraconazole are not tolerated in accordance with local protocol. In addition use for treatment is restricted to patients in whom there is a specific risk of Aspergillus infection or where fluconazole or itraconazole are not tolerated on the advice of local microbiologists or specialists in infectious diseases.

 

It is available as 100mg tablets and 40mg/ml oral suspension.  The MHRA Drug Safety Bulletin warns that the doses of tablet and oral suspension formulations of posaconazole are not directly interchangeable due to differences in dosage frequency, administration with food and plasma drug levels achieved.  The labelled oral dosage of posaconazole is: 

  • tablet: 300 mg/day (after a loading dose on day 1 of 600 mg/day)
  • oral suspension: 600–800 mg/day

 

If tablets are substituted for suspension at the same dose there is a risk of toxicity, and if suspension is substituted for tablets at the same dose there is a risk of under dosing infection as a result.  There have so far been 3 reports of such dosing errors in the UK.

 

Product information for posaconazole is being updated and the outer cartons of the oral forms have also been revised to better distinguish the tablets from the oral suspension, and to include a warning statement that the products should not be substituted for one another without adjustment of the dose.

 

 

 

 

Published 19/12/16