Flash VIG-news: pay attention to the elimination half-life of hydroxychloroquine and chloroquine and to the risks of drug interactions

As mentioned in the AFMPS news of 24.03.2020, hydroxychloroquine (Plaquenil) and chloroquine are used in certain circumstances to treat patients with COVID-19. The FAMHP reminds everyone of the risks of drug interactions posed by these treatments.

According to the Sciensano treatment guidelines, use of hydroxychloroquine (Plaquenil) and chloroquine to treat COVID-19 must be initiated in hospitals. It is very important that healthcare professionals only use hydroxychloroquine and chloroquine for authorised indications or as part of clinical trials or emergency measures for treating COVID-19. Major clinical trials are underway to generate robust data to determine the efficacy and safety of chloroquine and hydroxychloroquine in the treatment of COVID-19.

Available stocks of these products in Belgium have also been quarantined by the FAMHP to ensure controlled distribution. In some cases, treatment may be continued at home after discharge (in this case, the medication is provided to patients by the hospital).

Hydroxychloroquine and chloroquine have a complex and variable pharmacokinetic profile and a relatively lengthy elimination half-life (up to 30 days). This must be taken into account particularly as regards the risk of drug interactions.

Pharmacokinetic drug interactions

Hydroxychloroquine is a substrate and inhibitor of CYP2D6. The concomitant administration of modulators (inhibitors or inducers) of this enzyme should be avoided during treatment with hydroxychloroquine and must be undertaken with caution (up to several days) after stopping treatment with hydroxychloroquine. Known CYP2D6 inhibitors include antidepressants such as fluoxetine, paroxetine and bupropion, antiarrhythmic drugs such as propafenone, anti-retroviral drugs such as ritonavir, antihistamines such as diphenhydramine and antimycotics such as terbinafine. Used in combination with hydroxychloroquine, these increase plasma levels of hydroxychloroquine and the risks of adverse effects associated with this molecule.

Pharmacodynamic drug interactions

Medication with adverse effects similar to those of chloroquine and hydroxychloroquine, e.g. medication that can prolong the QT interval (i.e. azithromycin), hypoglycemia, lowered seizure threshold or retinopathy must be used with caution, even after stopping treatment with hydroxychloroquine and chloroquine.

Expected drug interactions with medication used to combat COVID-19 can be consulted at http://www.covid19-druginteractions.org/.

Messages for patients

Self-medication should be avoided. Medication containing chloroquine and hydroxychloroquine can entail toxicity, particularly cardiac toxicity.

Do not take this medication without talking to your doctor first.

Many counterfeit anti-COVID-19 medication are circulating on the internet. Do not buy any of these.

Adverse effects should be notified to the FAMHP

Patients and healthcare professionals are urged to report suspected adverse effects via www.notifieruneffetindésirable.be.

For more information

News 24.03.2020

 

 

 

Last updated on
06/04/2020