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Information on oral Antihistamines including Antihistamine uses and side effects.
Antihistamines are a group of medications which can be used for the following conditions:
Some Antihistamines, such as Chlorpheniramine, Dexchlorpheniramine, Tripolidine, Diphenhydramine, Hydroxyzine and Promethazine may cause drowsiness.
Other newer Antihistamines, such as Cetirizine, Loratadine, Fexofenadine, Desloratidine and Levocetirizine are less likely to cause drowsiness
While some Antihistamines may be available over-the-counter, other Antihistamines require a doctor’s prescription.
If you forget to take a dose, take it as soon as you remember. Then take your next dose at the usual time. Do not take two doses to make up for the missed dose.
Inform your healthcare professional if:
The symptoms of a drug allergy to Antihistamines include one or more of the following:
If you experience any of these symptoms, you should stop taking Antihistamines and see your healthcare professional immediately.
If you continue to experience symptoms for more than 2 weeks even with self-treatment or have any of the following symptoms:
Your condition may be too serious for self-treatment and you should consult a doctor
If you are taking a type of medication known as monoamine oxidase inhibitors (e.g. Rasagiline), contact your healthcare professional before taking Antihistamines containing chlorpheniramine or brompheniramine as your blood pressure may drop dangerously low
Taking Antihistamines with alcohol may worsen the drowsy side effect. Avoid all alcohol while on Antihistamines.
Many over-the-counter medications contain Antihistamines, always check with your health care professional before taking two over-the-counter medications at the same time to prevent overdosing.
Store in a cool and dry place, away from direct sunlight. Keep Antihistamines away from children.
Pack Antihistamines into a black trash bag and seal it tightly before throwing it into the rubbish chute or bin.
If you take more than the recommended Antihistamine dosage, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.
This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore.
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This article was last reviewed on
Thursday, February 25, 2021