allergy attack

[cellio]

I'm allergic to Pennsic. (Well, to dust and grass and pollen and weeds and...) So I take Allegra for about three weeks each year to deal with that, but don't take it the rest of the year. (I don't want to develop a resistance to it like I did to all previous allergy drugs save one [1].)

This year I started taking it on Saturday, and then went to Cooper's Lake Sunday for setup. I was fine yesterday, but today I've been congested all day. Mid-day I added Sudafed to the mix; I hope that wasn't bad but I really needed to treat the symptoms. (I take the Allegra once a day and had taken it this morning.) It took about four hours for the Sudafed to produce results.

I think this must have happened in the past, because there's Sudafed in with my use-only-at-Pennsic stuff. Now that I think about it, I remember once calling my doctor from Pennsic to ask if taking Sudafed while taking Allegra would kill me and he said it wouldn't.

I don't know if starting the Allegra earlier would help; how long does it have to be coursing through your veins to lay down a basic barrier against the nasty little allergens? With luck, writing this entry will help me remember next year to start earlier. (I'm sort of assuming that I should be taking allergy drugs (Allegra) and not cold drugs (Sudafed) as a baeline. I don't have a cold; I just have some of the symptoms.)

I should remember to ask my doctor if he can improve on this for me.

[1] Seldane. It worked gloriously, better than Allegra I think, so naturally the FDA eventually decided I couldn't have it.

Comments

[(Anonymous)]

how long does it have to be coursing through your veins to lay down a basic barrier against the nasty little allergens?

About an hour. Peak blood serum concentrations are reached (on average) in 2.6 hours. FYI, the laws of steady-state metabolism means that it takes about 5 half-lives for steady-state to be reached. I recall that you've taken enough math to know what I mean, but I don't remember if you remember the math in question. In general, if the drug is supposed to last 12 hours and you take it every 12 hours, it'll take (5x12, or 60) hours for you to reach the maximum amount in your body, and thus maximum effectiveness. It works in reverse as well. If you were at maximum blood levels, and you stopped taking it, it'll all be out of your body in the same amount of time.

Be lucky that antihistamines aren't as bad as amiodarone. Amiodarone has a 51-day half-life.

D'oh!

[sethcohen.livejournal.com]

Of course, that was me. I'm responding from Karen's computer, which can be placed under a fan or air conditioning (or, in this case, both). I'm warm.

[cellio]

Thanks for the information! Ok, next year it sounds like I need to start Thursday (for a Sunday exposure). Could be Friday, but they're one-a-day pills so better 12 hours too much than 12 hours too little. :-)

I hadn't considered the flip side; I've always taken the drugs for a few days past the end of Pennsic on the theory that all that stuff bombarding my body probably has lingering effects. But, as you say, the drugs also linger. So maybe I can stop taking it the day I come home. Hmm.

Amiodarone has a 51-day half-life.

Yowsa. What is it used to treat?

[sethcohen.livejournal.com]

Whoa...remember that it's still 5 half-lives. If the drugs lasts for 24 hours, then you need to take it for 5x24 hours, or 5 days to reach maximum potency.

Amiodarone is used to treat a kind of heart arrythmia. :)

[cellio]

Oh, oops. You're right. Allegra comes in both 12-hour and 24-hour varieties, and somehow I thought you were saying that the half-life of Allegra is 12 hours rather than a particular delivery vehicle.

(I don't know if 24-hour drugs really last 24 hours. I'm torn on when in the day I should take it -- first thing in the morning for maximum effect while I'm awake, or evening so that I won't wake up with sniffles? Assume I'm running around enough to make, say, hitting 2pm consistently impractical. I'm currently taking it in the morning.)

[jerusha.livejournal.com]

According to my pocket reference, the elimination half-life of fexofenadine (the active ingredient in Allegra) is 14.4 hrs. So you would need to start your dosing 72 hours in advance of exposure. So if you'll be on site Sunday, you should start taking it on Wednesday night or Thursday morning.

[sethcohen.livejournal.com]

As your allergies are situational, I'd recommend taking it in the morning. It takes a bit for your immune system to respond to the pollen insult, so the antihistamine will already be in your blood by the time it's thinking about responding. If you had allergies related to being home (e.g. dust mite allergy) I'd recommend you take the Allegra in the afternoon or evening.