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Doctor insights on: What Is The Highest Dosage Of Antihistamine That One Person Can Take At One Time

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What is the highest dosage of antihistamine that one person can take at one time?

What is the highest dosage of antihistamine that one person can take at one time?

Antihistamines: Safety of high dose medications is often unknown. Our experience comes from case reports of persons who intentionally or accidentally consumed unusually excessive quantities. When Claritin (loratadine) was first investigated, safety studies were done at 40 mg (4 times the current recommended dose). We take 10 mg because effectiveness is not significantly different between 10 mg and 40mg. ...Read more

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Dr. Paul Carter
627 doctors shared insights

Antihistamine (Definition)

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


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How many milligrams of antihistamine can a person take at one time?

How many milligrams of antihistamine can a person take at one time?

Unclear: Different antihistamines have different potencies. 10 mg of Zyrtec is equivalent to 180mg of Allegra (fexofenadine). Mg doseage as in all medicines are drug specific. In regard to toxic levels, each has it's own known limit. However too much antihistamine can lead to deadly arrythmias/ Please use the recommended dose. ...Read more

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Can you take generic multi symptom night time medicine with night time Thera-Flu? I don't usually get drowsy from just one dose of antihistamine. I have adhd so it's hard for me to get sleepy from that. So is it okay to take both?

Can you take generic multi symptom night time medicine with night time Thera-Flu? I don't usually get drowsy from just one dose of antihistamine. I have adhd so it's hard for me to get sleepy from that. So is it okay to take both?

No: Those preparations contain multiple drugs similar to thera-flu, the problem isn't with antihistamines only, other components could interact, or interact with whatever medicines you are on or if you are under treatment for adhd, please consult your doctor and read the labels carefully, good that you asked , always exercise caution with multiple medications, ...Read more

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Would I benefit from imatrex as to just taking tylenol for my migraines? Usually behind one eye, zig zag around eyes, nauseated, throwing up at times. Can not take antihistamines, or OTC cough meds. gives me heart palpatations. Although I do use Alaway an

Would I benefit from imatrex as to just taking tylenol for my migraines? Usually behind one eye, zig zag around eyes, nauseated, throwing up at times. Can not take antihistamines, or OTC cough meds. gives me heart palpatations. Although I do use Alaway an

Yes: Tylenol (acetaminophen) does not really work that well for migraine and thus Imitrex would likely be far more effective. The earlier the better. Sometimes adding a NSAID may provide added benefits. If nausea prevents you from swallowing Imitrex , ask for a nasal spray version. ...Read more

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Is it ok to take Clorazepate with an antihistamine? The dosage is 3.75mg.

Is it ok to take Clorazepate with an antihistamine? The dosage is 3.75mg.

Watch for drowsiness: The combination can cause increased drowsiness. Please do not drive while taking both. Avoid the use of alcohol in combination. The clorazepate can be habit forming. ...Read more

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What dosage of antihistamine should I take to resolve a mild food allergy reaction?

What dosage of antihistamine should I take to resolve a mild food allergy reaction?

Any recommended: Dosage of any OTC antihistamine, either first or second generation, will be effective, more important though is avoidance of re-exposure to the offending food till problem is sorted out. Keep antihistamine handy for accidental exposure, if severe reaction, keep epipen (epinephrine) handy too, see your doctor/allergist if the problem is bothersome, best wishes ...Read more

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What is the best time to take an antihistamine?

Any time: You can take antihistamines any time of the day.Take them same time of day everyday. ...Read more

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I know it is not recommended to take more than one antihistamine pill per 24 hours, but some only last ~8 hours. Which ones lasts for 24 hrs?

I know it is not recommended to take more than one antihistamine pill per 24 hours, but some only last ~8 hours. Which ones lasts for 24 hrs?

Xyzal (levocetirizine) and Clarinex: From experience some of the newer antihistamines such as Xyzal (levocetirizine) and Clarinex seem to be effective for longer time periods. Most antihistamines however peak in effectiveness in the first few hours and start to wear off after 12-15 hours. ...Read more

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I am about to take an antihistamine for the first time but my friends tell me to use it before bedtime. Will I still feel the effects the next day?

Depends on the med: Some antihistamines are more sedating than others. Medications like Benadryl (diphenhydramine) can definitely cause sedation. Newer antihistamines like Allegra and Claritin are non-sedating and Zyrtec is sedating in roughly 10-20% of patients. ...Read more

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Can i take citalopram and antihistamine at the same time?

"Can I": "I" is the catch in your question. I can't give advice to you in particular. The answer depends on your other known conditions and the Celexa dose. For an otherwise healthy person, 30mg daily of Celexa or less plus an antihistamine at standard dose carries a low risk for heart problems. Discuss with your doctor and the pharmacist dispensing the Celexa before going forward with the combo. ...Read more

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Can i take citalopram and antihistamine at the same time?

Can i take citalopram and antihistamine at the same time?

Probably: This combination is usually safe, but individual factors may influence this. Consult your doctor to deal with your specific circumstances. ...Read more

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Can i take an antihistamine and a decongestant at the same time?

Can i take an antihistamine and a decongestant at the same time?

Yes: Many allergy medications already combine an antihistamine with a decongestant. These include Claritin (loratadine) d, Allegra d, zyrtec d, etc. The d stands for decongestant. ...Read more

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Do people take an antihistamine and a corticosteroid at the same time?

Do people take an antihistamine and a corticosteroid at the same time?

Yes: And the treatment should be under medical guidance, dosage of steroids need to be dictated by your treating physician. ...Read more

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When is the best time to take an antihistamines for an allergy? Why?

When is the best time to take an antihistamines for an allergy? Why?

It depends: It depends on the antihistamine and when you are exposed to the cause for your allergies. Antihistamine pills generally take at least 30 minutes to two hours to take effect and peak hours later. Pollen levels are highest in the morning, but if you are exposed to other allergens such as animal dander or dust, those levels would affect you at night. Take it a few hours before your worst time. ...Read more

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Can i take one antihistaminic at moorning and another one at nigt? for alergic reactions.

Can i take one antihistaminic at moorning and another one at nigt? for alergic reactions.

Yes but...: Antihistamines can be taking twice a day safely if required but there are other treatments available. If by allergic reaction you are referring to seasonal allergies, the gold-standard therapy is daily nasal steroid sprays and/or antihistamine nasal sprays. Nasal saline rinses, avoidance measures, and if refractory to treatment, allergy shots can also be helpful. See an Allergist for more details. ...Read more

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Hi..i took three antihistamines by mistake when i was told to take only one at night. is this dangerous? each tablet is 120 gms

Hi..i took three antihistamines by mistake when i was told to take only one at night. is this dangerous? each tablet is 120 gms

Likely Ok: Antihistamines have a high safety margin although the older antihistamines may have more side effects. It is unusual to have mistakenly taken 3 pills when most medication is based on 1 pill. You will have to be more careful in the future since other medications may not be as forgiving. ...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 are going to be skin tested for allergies to either drugs, inhalants (such pollens), or foods extracts ...Read more

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I am on prednisolone, hydroxycloroquine and an nsaid. Can i take antihistamine at the same time?

I am on prednisolone, hydroxycloroquine and an nsaid.  Can i take antihistamine at the same time?

Maybe but it depends: I can't answer your question exactly b/c you didn't specify NSAID or antihistamine. Check out both www.Online.Epocrates.Com & www.Drugs.Com to check for medication interactions. Plug in what you're taking and both websites will warn you of possible interactions. They're not 100% foolproof but they're a good start. Better yet, ask whoever prescribed your meds. Always tell ur doc what you're taking! ...Read more

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Is it safe to take two 24-hour antihistamine pills at the same time?

Is it safe to take two 24-hour antihistamine pills at the same time?

Depends: It could be safe or not depending on the total dose you are taking in one day. By the way safe is conventionally defined, it will probably be safe and it will at most make you a little sleepy and contribute to reduced motor coordination, but in the context of operating a motor vehicle this could make a difference. You may want to see a doctor to get your allergies evaluated medically. Stay safe! ...Read more

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If i take an antihistamine, would this stop an allergic reaction? (if taken 30mins/1hr beforehand with enough time to take effect)

If i take an antihistamine, would this stop an allergic reaction? (if taken 30mins/1hr beforehand with enough time to take effect)

Prevent allergic rxn: Don't count on it. That might work, but it could be very dangerous--fatal! you need tests to determine your allergies and if you want to challenge yourself after that, you should do it in an allergist's office. Better idea: take shots for inhalant allergies that cross react with foods and then retest the foods. The level of allergy could decrease, making it safer for you to eat the fruit again. ...Read more

Apex (Definition)

Apex normally refers to a peak. However in dentistry it actually is defined as the end ...Read more