I got prescribed this in 280mg tablets, OTC is only 120mg. For urticaria not typical allergies. I found it's not 24 hours but would effectively run out before the day is over I took one of the higher prescription version per day. I haves since gone back to loratidine taking up to 4 one a day tablets a day as it is licensed for urticaria at this frequency.
Imho this drug works quicker after taking but doesn't last a full day. This is for urticaria but I also need antihistamines for various other allergies so I'm talking about its effect on say hayfever or dust mite allergic response as well as urticaria. If you can live with shorter effectiveness to benefit from faster acting then consider it.
My advice is to speak to your pharmacist. This is pharmacist territory. Unfortunately we as a nation use pharmacist less than other nations. A lot of nations use pharmacist as a triage service even down to sending to hospital instead of GP. Basically closer to how we use a GP than how we use a pharmacist as a pill pusher. They can do a lot more than we often use them for.
