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Beware of mix-ups between products containing mirtazapine and mianserin

31 August 2009

The Danish Medicines Agency has been informed through the Danish Patient Safety Database of six adverse incidents in the period from March 2007 to June 2009 involving the mix-up of medicines containing the active substances mirtazapine and mianserin.
The reasons for the mix-ups are described as follows:

  • The pronunciation of the names sound alike
  • The names look alike, especially when hand-written
  • The ATC codes are almost the same - antidepressants
  • They are placed near to each other in the medicine room because the ATC codes are almost identical

One report describes a patient who had been administered 15 mg mirtazapine instead of 15 mg mianserin. The two products were confused with one another because they had been placed under the same ATC code in the medicine room and had comparable names. At the same time, the medicine room was busy when the medicine was dispensed.

Medicines containing the active substances mianserin and mirtazapine have many similarities, but they are not interchangeable. The dosage regimen is different, and the side-effect profile and interactions are not identical. The two active substances are summarised below:

 

Mianserin

 Mirtazapine

ATC code
N06AX03 – Antidepressants, block of adrenergic receptors (NaSSA)
N06AX11– Antidepressants, block of adrenergic receptors (NaSSA)

Type of substance


tricyclic antidepressant 

 piperazino azepine
Example of dosage Adults
Individual. Initially, 30-40 mg per day and dose adjustment according to clinical response.
Maintenance dose is usually 30-90 mg per day.

Aged patients
Initially, maximum 30 mg per day. Dose increase should be effected slowly and under close monitoring.

Adults
The recommended initial dose is 15 mg or 30 mg, taken at night. Maintenance dose is usually between 15 mg and 45 mg per day.


Aged patients
The same as for adults. Any changes, particular dose increases, should take place carefully and under close monitoring.

Sources: 1) Infomatum A/S - www.medicin.dk  2) Martindale - the Complete Drug Reference

 

There are several pharmaceutical companies that manufacture medicines containing the active substances mianserin and mirtazapine. The name of the medicine may not be the same as name of the active substance, e.g. Tolvon from the company Organon (mianserin) and Mirtin from the company KRKA (mirtazapine).

It is crucial that the name and strength are always cross-checked before administered to the patient, just as the medicine rooms must be calm while the medicine is dispensed. It could be considered whether it is necessary to store both medicines in the room as standard.

With this announcement, the Danish Medicines Agency wishes to increase focus on the safety related to the general handling of these products.

Danish Medicines Agency, 31 August 2009