TGA issues medicines safety update

Pharmacists have been reminded that first-generation oral sedating antihistamines are not approved for use in kids under two

Following a coronial hearing of a fatal case involving a 74-day-old infant being given OTC promethazine oral liquid, the TGA has recently reviewed the safety of the medicine in infants.

While the Coroner did not attribute the infant’s death to ingestion of promethazine, they were concerned about the risk of respiratory depression when promethazine is given to infants, and therefore recommended stronger PI and CMI warnings.

The TGA’s investigation found that while most promethazine oral liquid products do have warnings on their labels advising against use in children under two years, there is still a need to improve safety measures.

It will be seeking to make the statement ‘Do not give to children under two years of age’ a mandatory warning statement on the labels of all OTC liquid oral formulations of first-generation oral sedating antihistamines.

The risk of respiratory depression in infants also applies to other first-generation oral sedating antihistamines, including: brompheniramine; chlorpheniramine; dexchlorpheniramine; diphenhydramine; doxylamine; pheniramine; alimemazine (trimeprazine); and triprolidine.

As of 15 November 2017, the TGA database contained 45 reports of adverse events in children aged under two in which a first-generation oral sedating antihistamine is listed as the sole-suspected medicine, with adverse events including hypersensitivity reactions, agitation, abnormal movements, vomiting and diarrhoea.

The TGA reminds health professionals that these products should not be prescribed or recommended to children under two years of age.

They are encouraged to discuss the issues with parents and caregivers, and report any adverse events involving the medicines to the TGA.

Other safety updates include:

Suvorexant (Belsomra) next day effects

Since registration of insomnia treatment Belsomra on the ARTG in November 2016, the TGA has received a number of adverse events reports, including sleep paralysis, gait disturbance, hallucination, headache and paraesthesia.

Potential side effects, including next day residual effects, are well communicated in the PI, but it’s important for patients to be warned of them, reminds the TGA.

Patients should also be reminded not to take the medication if they are drinking alcohol that evening or before going to bed, or if they have taken other medicines that make them sleepy, as it may increase risk of these adverse events occurring.

Miconazole and potential interaction with warfarin

Health professionals are reminded that, while the number of Australian reports is low, the potential interaction between miconazole and warfarin can be life-threatening.

The antifungal miconazole is used to treat ringworm, pityriasis versicolour, and yeast infections of the skin or vagina.

Three products affected by this issue are:

  • Daktarin Oral Gel
  • Decozol Oral Gel
  • Resolve Thrush Cream

Potential for interaction between miconazole and warfarin is “well-documented”, says the TGA.

It inhibits one of the main isoenzymes involved in warfarin metabolism, leading to potentially fatal bleeding events.

The TGA is seeking to make the statement ‘Ask your doctor or pharmacist before use if you are taking warfarin, a medicine used to thin the blood, because bleeding or bruising may occur’ a mandatory warning statement on these products.

It will also work with sponsors to strengthen the warnings in the PI and CMI documents for these products.

In the meantime, health professionals are encouraged to discuss this issue with patients.

Desvenlafaxine (Pristiq) recommended dose

Health professionals are reminded that the recommended dose of desvenlafaxine (Pristiq and generic versions) is 50 mg once daily and that the maximum dose should not exceed 200 mg/day.

The PI for Pristiq has recently been updated to reflect this.

Prescribing above this dose may increase the risk of patients experiencing adverse events.

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