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Doctor insights on: Long Acting Antihistamines

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Benadryl (Definition)

Diphenhydramine is a sedating antihistamine which is a kind of antihistamine type drug (common ...Read more


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Are there any immediate acting allergy medications I can take other than Benadryl (diphenhydramine)?

Are there any immediate acting allergy medications I can take other than Benadryl (diphenhydramine)?

Several: OTC second generation antihistamines as cetirizine and loratadine, but read the labels and instructions carefully ...Read more

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Am taking 24hr alegra but my allergies still act up at night, so I take a Benadryl (diphenhydramine) at night too?

Am taking 24hr alegra but my allergies still act up at night, so I take a Benadryl (diphenhydramine) at night too?

Allergic rhinits: Instead of benadryl, (diphenhydramine) I recommend you to ask your doctor for a prescription of a nasal steroid to use once a day. Examples are flonase, nasaonex, Qnasl and nasacort. Another class of medicines your doctor can try is singulair, 10 mg, taken once a day. ...Read more

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I wanted to know I took benadryl (diphenhydramine) because my allergies are acting up and I'm stuffed up, I have a cough, I'm weeding because my asthma as well. Is it o?

I wanted to know I took benadryl (diphenhydramine) because my allergies are acting up and I'm stuffed up, I have a cough, I'm weeding because my asthma as well. Is it o?

Probably not: I presume you are asking whether it is ok to do some weeding when your nose is stuffed up and your asthma is not controlled. In general, the answer would be no since you are likely allergic to weed pollen and molds from the disturbed soil. It is also important for you to call your doctor about your asthma. Benadryl (diphenhydramine) or any other antihistamine has no decongesting action, nasal steroid does. ...Read more

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Just took 25 mg of Benadryl (diphenhydramine) will that counter-act/ make my Prozac and klonopin that I took earlier not effective?

Just took 25 mg of Benadryl (diphenhydramine) will that counter-act/ make my Prozac and klonopin that I took earlier not effective?

No it won’t: Taking benadryl (diphenhydramine) in addition to prozac and klonopin will not counteract the effects. Just be careful with taking it too close to the klonopin because they both cause drowsiness. ...Read more

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My doctor prescribed me trazodone 100 mg for sleep and I am now experiencing pins and needles all over. I took 4 Benadryl (diphenhydramine) to counter act.

My doctor prescribed me trazodone 100 mg for sleep and I am now experiencing pins and needles all over. I took 4 Benadryl (diphenhydramine) to counter act.

Oversedating: It is not a good idea to combine sedating medications. The trazadone was given to help you sleep and taking additional 4 Benadryl (diphenhydramine) which I assume is 100mg will add too much extra sedation on top. If the side effects of trazadone are bothersome I recommend discussing other options with your doctor instead of taking a lot of other medications to mask symptoms. ...Read more

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Is taking antihistamine everyday bad for you in the long term? Will my immune system get impaired?

Is taking antihistamine everyday bad for you in the long term? Will my immune system get impaired?

No and no.: There are no known longterm sequellae from antihistamines. I would stick with the long-acting, non-sedating ones, such as Allegra and Claritin, (loratadine) since the short-acting ones can make you drowsy. Antihistamines do not affect the immune system in any measurable way. ...Read more

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What amount of does take to get high off of diphenhydramine hci/antihistamine and how long does it take to kick in?

What amount of does take to get high off of diphenhydramine hci/antihistamine and how long does it take to kick in?

Varies: Varies with dose. Some people get sleepy at lower dose than others. Some people get jumpy instead, especially children. Also depends on interaction with other meds or alcohol or caffeine. ...Read more

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I have been congested for 10 days -- much longer than a regular cold. Antihistamines help a little. What else can I try?

Still a cold: A viral upper respiratory infection may last up to 2 weeks, although usually it lasts less. Beyond 2 weeks symptoms may suggest allergy or complicating sinus infection. Antihistamines don't work well for colds. You may try nasal irrigation with saline, even a nasal decongestant such as oxymetazoline (afrin) for no more than five days. If no better then, see a physician. ...Read more

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How many weeks does it take for claritin (loratadine) 10mg to work? How long should I give it a try before deciding to switch to a different antihistamine?

How many weeks does it take for claritin (loratadine) 10mg to work? How long should I give it a try before deciding to switch to a different antihistamine?

Try for a few days: Antihistamines begin to work in less than an hour but a person may not feel significant relief for a few days. Claritin tends to be one of the weaker non-drowsy antihistamines. Others available without a prescription are Zyrtec, Allegra and Xyzal. If antihistamines are still not working then an evaluation by an allergist can be helpful to determine the cause of symptoms ...Read more

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How long do antihistamines stay in your system?

72 hrs: The biologic effects no longer than 72 hours even though the drug may still be detectable for up to a couple of weeks with certain antihistamines. ...Read more

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Do antihistamines lose effectivness after prolonged use?

Do antihistamines lose effectivness after prolonged use?

No: Antihistamines bind to histamine receptors without activating the receptor thereby blocking ability of histamine to bind to the receptor and activate it, causing itching and blood vessel dilatation (producing redness and swelling of affected tissue). The ability of the antihistamine to bind to the histamine receptor doesn't decrease over time. Increased symptoms due to increased allergen exposure. ...Read more

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Can you tell me the safest antihistamines for long term use?

Many: All of the newest generation of antihistamines like Zyrtec, Claratin, Allegra, Xyzal, (levocetirizine) or Clarinex are very safe for long term use. ...Read more

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What consequences result from using antihistamines long term?

What consequences result from using antihistamines long term?

Break: What do you mean long time? Its good to give break to antihistamine, do saline rinse b, use pnaris nasal emollient with q-tip, wear a mask in yard and car, house carpet free bed room. All pills have side effects. Effects are they dry you up s/e many. ...Read more

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How long does it take antihistamines to get out of your system? I was told not to take any for 1 week, but inadvertently did. Is 5 days enough time?

How long does it take antihistamines to get out of your system? I was told not to take any for 1 week, but inadvertently did. Is 5 days enough time?

Yes: Most antihistamines clear within 2 -3 days or less, 1 week is a precautionary measure to make sure that your system is clear, that's mainly if you are going to be skin tested for allergies to either drugs, inhalants (such pollens), or foods extracts ...Read more

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What are long term side effects of diphenhydramine antihistamines and do they lose effectiveness over time? K

Minimal: Diphenhydramine is the active ingredient in Benadryl (diphenhydramine) and has been around for a very long time. Like most antihistamines, there is not believed to be long term side effects. Losing effectiveness is less well studied, but with ongoing use there could be some development of tolerance or it could be that you are still being exposed to an allergen and that is why symptoms are not controlled. ...Read more

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How long will it take for prolactin levels (17.5 in male) to drop after discontinuing high doses of antihistamine for three consecutive months that caused elevated numbers? Will hair stop shedding?

How long will it take for prolactin levels (17.5 in male) to drop after discontinuing high doses of antihistamine for three consecutive months that caused elevated numbers? Will hair stop shedding?

If it was: Due to the antihistamine, which a doubt, it should be relatively quickly over days. Also, it is unlikely that that is the cause of your hair loss. Check w/your doctor for other explanations for all of your concerns. ...Read more

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What is the safest antihistamine for long term use?

What is the safest antihistamine for long term use?

New generation ones: Antihistamines in general are very safe. New generation products (Zyrtec, Claritin, (loratadine) Allegra, Xyzal) are just as effective with less side effects than older antihistamines (Benadryl, chlorpheniramine, hydroxyzine). However, it would be important to address WHY a person needs to take antihistamines long term? Consult with an allergist to assist in identifying the cause of symptoms. ...Read more

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How long until an antihistamine works on post nasal drip?

THEY WON'T HELP MUCH: Other than drying it up a bit and thickening it, which can cause cough. The key in trying to eliminate postnasal drip is to cut the inflammatory or environmental response that it is caused by. ...Read more

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Is there any side effects when you take antihistamines for a longer period than a month?

Unlikely: Antihistamines are generally safe to take for prolonged periods of time, as long as you're taking the proper dose. These medicines are notorious for causing drowsiness, although some over the counter antihistamines are non-drowsy. ...Read more

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Is it OK to take multiple types of antihistamines within a 24-hour period? Nothing seems to work as long as advertised.

DETAILS?????: What are you treating? Which antihistamines? How many of each? There are easy answers after the details are given. No answer is possible without this information. For chronic urticaria I may manage it with 10 or 20mg cetirizine (Zyrtec) in AM and hydroxyzine at bedtime. I never use Benadryl (diphenhydramine) except as a sleeping pill. ...Read more

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Is qnasl an antihistamine? Is it safe to eat grapefruit and use it? If not how long must one wait after eating it to use it?

Is qnasl an antihistamine? Is it safe to eat grapefruit and use it? If not how long must one wait after eating it to use it?

Nasal steroid spray: Qnasl is a steroid nasal spray and not an antihistamine. It is safe to eat with grapefruit and any other food. No food interactions. The good effect of nasal steroids may take a couple of days to notice and peak in about a week. Qnasl is one of 2 nasal steroid sprays that is "dry" rather than wet. ...Read more

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How long to take antihistamines to get rid of hives?

How long to take antihistamines to get rid of hives?

Depends: If it is truly hives then you should notice an improvement soon after taking med....If no improvement or worsening then see your doctor. ...Read more

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How long does it take for antihistamines to work on your itchy rash?

How long does it take for antihistamines to work on your itchy rash?

IF they work. Fast.: Oral and especially topical antihistamines may have a slight- if any- effect on itching and will be noticeable quite soon after use. ...Read more

Dr. Paul Carter
648 Doctors shared insights

Antihistamine (Definition)

Sedating and non-sedating antihistamines prevent and treat allergic reactions, and are ...Read more