Little role for sedating antihistamines: Experts

pharmacist sneezes

Newer, less sedating forms can be safely taken long term with no loss of efficacy, according to latest evidence

In a new article for Australian Prescriber, immunology experts have concluded there is now “little role for sedating antihistamines in allergic conditions”.

While early ‘first generation’ antihistamines such as promethazine cause sedation, this is less of a problem with newer ‘second generation’ antihistamines such as loratadine, and ‘third generation’ ones such as desloratadine.

Less sedating antihistamines are equally efficacious as first generation ones and can be safely taken long term, says Associate Professor Katrina Randall from ANU Medical School, and clinical immunologist Dr Carolyn Hawkins from Canberra Hospital.

The unfavourable adverse effect profile of sedating, first generation antihistamines has also prompted the Global Allergy and Asthma European Network to recommend making these antihistamines prescription-only, rather than over-the-counter, they write in an article for Australian Prescriber.

Sedating antihistamines have been linked to:

  • Interference with REM sleep
  • Poorer school performance
  • Increased aviation accidents
  • Increased car accidents
  • Behavioural and other adverse effects in children less than two years (particularly with promethazine)
  • Anticholinergic effects
  • Severe tissue injury, including gangrene, with both intramuscular and intravenous injection (particularly with promethazine)

“The main role for sedating antihistamines is in pregnancy, where they can be used for any of the common indications for antihistamines, as they have the strongest evidence of safety,” say A/Prof Randall and Dr Hawkins.

“They have been taken by a large number of pregnant women and women of childbearing age without any proven increase in malformations or harm to the fetus.

“An exception is promethazine for which adverse events have been reported in animal studies (at very high doses).

“However, pregnant women must be warned about the other aspects of safety such as sedation and consider whether they should not drive while taking these drugs. The newer antihistamines are likely to be as safe in pregnancy but have not been used by as many women, so they do not have the same evidence of safety.”

Cetirizine is one of the newer antihistamines most likely to cause sedation, they say, particularly in higher doses.

Meanwhile, the authors remind readers that there is no role for antihistamines for cold and flu symptoms, nor for acute management of anaphylaxis.

Read the full article here.

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