Press Release

Caution with the use of two drugs and serotonergic psychiatric medications

27 Jul 2011

The Department of Health (DH) today (July 27) cautions the public about the use of two drugs, methylene blue injectable and Zyvox (linezolid,) after assessing safety alerts issued by the United States (US) drug authority, the Food and Drug Administration (FDA).

From surveillance, the DH learns that the USFDA is also warning against the use of methylene blue injectable or Zyvox (linezolid) after reports of serious central nervous system reactions are received when the two drugs are given to patients taking psychiatric medications that work through the serotonin system of the brain.

The group of serotonergic psychiatric medications involved include selective serotonin reuptake inhibitors (e.g. paroxetine, fluoxetine, sertraline, citalopram), serotonin-norepinephrine reuptake inhibitors (e.g. venlafaxine, duloxteine), tricyclic antidepressants (e.g. amitriptyline, desipramine, imipramine, nortriptyline, doxepin, trimipramine), monoamine oxidase inhibitors (e.g. isocarboxazid, phenelzine, selegiline), and other psychiatric medications such as trazodone, bupropion, buspirone and mirtazapine.

A DH spokesman states that methylene blue injectable is used to treat methaemoglobinemia. Zyvox (linezolid) is an antibacterial drug used to treat infections, including pneumonia and infections of the skin. Both are reversible monoamine oxidase inhibitors (MAOI).

“Although the exact mechanism of the drug interactions are unknown, it is believed that when methylene blue injectable or Zyvox (linezolid) are given to patients taking serotonergic psychiatric medications, high levels of serotonin can build up in the brain, causing toxicity symptoms such as twitching, sweating and diarrhoea,” the DH spokesman deliberates.

In fact, the spokesman adds that the DH has already issued a press release and letters to healthcare professionals earlier on in February this year to inform them of the suspicion of interaction between methylene blue injectable and serotonin reuptake inhibitors after assessment on an alert released by Health Canada.

The spokesman confirms that in Hong Kong, Methylene Blue Injection (HK-59020) is registered under Sino-Asia Pharmaceutical Supplies Limited.

As for Zyvox (linezolid), there are three registered dosage forms, respectively as tablet (HK-48055), injectable (HK-48056) and granule (HK-48057). They are prescription items, registered under Pfizer Corp. HK Ltd.

So far, the DH has not received any adverse event report relating the use of the two drugs in patients taking serotonergic psychiatric medications.

However, in view of the FDA’s actions, the DH decides to issue another series of letters to inform doctors and pharmacists about the latest US position. They are also advised to report any side effect resulting from the use of methylene blue injectable and Zyvox (linezolid).

Moreover, the matter will also be discussed in the coming meeting of the Registration Committee of Hong Kong's drug authority, the Pharmacy and Poisons Board.

While the DH will closely monitor the developments of the issue, the spokesman urges patients to consult their healthcare professionals if in doubt or feeling unwell.