Posaconazole (Noxafil): tablets and oral suspension are not directly interchangeable

Switching from posaconazole oral solution to tablets has resulted in cases of dose-related toxicity, whereas switching from tablets to oral solution has resulted in underdosing and lack of efficacy.

Advice for healthcare professionals:

  • posaconazole tablets and oral suspension are not directly interchangeable
  • switching from oral suspension to tablets can lead to overdosing and serious adverse drug reactions, whereas switching from tablets to oral suspension can lead to underdosing and lack of efficacy
  • prescribers should specify the dosage form for posaconazole on every prescription
  • pharmacists should ensure that the correct oral form is dispensed to patients

Posaconazole (Noxafil) is a broad-spectrum triazole antifungal for the treatment and prevention of fungal infections.

Posaconazole is available as an oral suspension (40 mg/mL), tablets (100 mg), and concentrate for solution for infusion (300 mg).

Medication errors

In the UK, we are aware of 3 reports of medication errors related to substitutions of posaconazole tablets and oral suspension at the same dose. Two reports were patients prescribed posaconazole tablets but were dispensed the oral suspension; one patient developed an infection which may have been related to the underdose. The third patient was prescribed posaconazole oral suspension but was dispensed tablets, reporting headache and renal impairment.

Posaconazole tablets and oral suspension are not interchangeable because of differences between the two forms in dosing 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

Product information for posaconazole is being updated to clarify that the oral solution cannot be directly substituted for the oral tablet, or vice versa, at the same dose. 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.

Further information

Letter sent to healthcare professionals, July 2016

Article citation: Drug Safety Update Volume 10 Issue 2, September 2016: 2.

Published 15 September 2016