Pam asked
How long until Allegra-D 24hr is out of my system? This was recommended to me by the doctor at the urgent care clinic, but after one dose this morning I am not feeling well.
I have NO appetite, my face is tingling, I feel jittery and out of it, my mouth is so dry, I just don't feel well at all. I would rather have the allergies and congestion! Is there anything I can do to get this out of my system fast? It is really sending my anxiety through the roof.
Answer
Allegra-D is a combination product containing:
- Fexofenadine (Antihistamine)
- Pseudoephedrine (Nasal decongestant)
Allegra-D is available in two formulations over the counter:
- 12 Hour (Containing 60 mg fexofenadine & 120 mg pseudoephedrine)
- 24 Hour (Containing 180 mg fexofenadine & 240 mg pseudoephedrine)
Each product will have it's effect last about as long as marketed on the package (i.e. 12 hours for Allegra-D 12 Hour, 24 hours for Allegra-D 24 Hour). However, if you are having adverse effects from either product, they may last slightly longer than beneficial effects of the ingredients.
Onset And Duration Of Action Of Allegra-D
The onset of action of Allegra-D is about 1 hour, but can range from 30 minuted to 2 hours depending on the individual. The duration of action is around 12 or 24 hours, depending on the product. When side effects occur with Allegra-D, it generally is attributed to the pseduoephedrine component, which can cause the following in some individuals:
- Insomnia
- High blood pressure
- Increased heart rate
- Feeling of anxiety
Allegra-D tablets have a dual release mechanism. The Allegra (fexofenadine) component is immediately released while the pseudoephedrine component is slowly released from the tablet over a 24 hour time period. This is why often times, the side effects from the pseudoephedrine component can last for long periods of time as your body is constantly getting exposed to newly released drug (from the extended release tablet).
While the decongestant effects of Allegra-D will generally subside after 12 to 24 hours (depending on the product), the actual drug (pseudoephedrine) lasts in the body for considerably longer. The half-life (time it takes for 50% of the drug to be metabolized) of pseudoephedrine ranges from 9—16 hours.
It is generally accepted that it takes around 5 half lives for the drug to be completely eliminated from the body. This translates to 3-4 days. While you shouldn't expect adverse reactions to last exactly that long, they can persist for longer than the 24 hour duration of action (of the Allegra-D 24 hour product).
Lastly, studies show that taking Allegra-D with a high-fat meal significantly decreases blood concentrations of fexofenadine. This could potentially reduce the antihistamine effect of Allegra-D. The pseudoephedrine component doesn't appear to be affected by food. Drinking water and staying hydrated is the best way to try to eliminate the drug from the body as quickly as possible.
