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Oral Antihistamines

(I'm asking this question as it regards to my current pharmacy training)

Do Oral Antihistamines...

a) cause drowsiness in some people

or

b) all cause drowsiness

For those of you who may not know what an Antihistamine is, it is used to treat allergies such as:
Hayfever
Food allergies
Pet allergies
House dust mite allergies
Insect bites
Mould spore allergies
Also relieves the itchy rash of chickenpox

Reply 1

Speedbird2008

After a quick Google search, from BUPA:

" There are two types of antihistamines, the older ones that are sedating (e.g. chlorpheniramine), which have drowsiness as one of their main Side effects, and the newer non-sedating ones (e.g. loratadine), which rarely cause drowsiness. Other less common Side effects, from the sedating antihistamines in particular, are headache, difficulty in passing urine, dry mouth, blurred vision, and digestive tract problems such as feeling or being sick, constipation or diarrhoea. Rarely, some antihistamines can also cause palpitations and abnormal heart rhythms, high blood pressure, allergic reactions (such as swelling, rash, and breathing difficulties), dizziness, confusion, depression, disturbed sleep, tremor, convulsions, blood and liver disorders, and over-excitement in children. Children and older people are more likely to experience Side effects. Antihistamine preparations applied locally (i.e. to the nose, eyes or skin) can cause irritation."

Hope that helps!

:smile:

Reply 2

visesh

A)

It depends on whether the antihistamine can cross the blood-brain barrier, as antagonising the histamine receptors in the brain can lead to drowsiness. The first antihistamines were sedative, but the newer ones don't usually cause drowsiness.