The Department of Health (DH) today (July 27) cautioned the public about the use of two drugs, methylene blue injectable and Zyvox (linezolid), after assessing safety alerts issued by the US drug authority, the Food and Drug Administration (FDA).
From surveillance, the DH learned that the FDA is also warning against the use of methylene blue injectable or Zyvox (linezolid) after reports of serious central nervous system reactions received after the two drugs were 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 stated 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 mechanisms 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 said.
The spokesman added that the DH had already issued a press release and letters to health-care professionals 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 confirmed 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, as a 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 to the use of the two drugs in patients taking serotonergic psychiatric medications.
However, in view of the FDA's actions, the DH decided to issue another series of letters to inform doctors and pharmacists about the latest US position. They are also advised to report any side effects 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 urged patients to consult their health-care professionals if in doubt or feeling unwell.
(Reprinted from HKSAR Government web page:
http://www.info.gov.hk/gia/general/201107/27/P201107270227.htm )