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Doctor insights on: Anticholinergic Effects Of Antihistamines

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Newer antihistamines are not anticholinergic. So why are side effects like constipation often reported for claritin (loratadine) for example?

Newer antihistamines are not anticholinergic. So why are side effects like constipation often reported for claritin (loratadine) for example?

Less anticholinergic: Newer generation antihistamines like Claritin (loratadine) still have anticholinergic properties, but to a much lower degree compared with first-gen. Some patients remain highly sensitive to associated side effects.

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Anticholinergic (Definition)

Most drugs have some anticholinergic qualities, which means they interfere with the normal function ...Read more


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Why bilateral armpit rash after swimming 1 min? I cannot use antihistamines 'cos severe anticholinergic effects (dysphonia, dry mucose). Montelukast.

Why bilateral armpit rash after swimming 1 min? I cannot use antihistamines 'cos severe anticholinergic effects (dysphonia, dry mucose). Montelukast.

Topical creme: There are multiple topical compounded cremes and ointments containing antihistamines which can be applied locally but not get absorbed systemically. Ask your doctor to prescribe some.

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Safe for a person who takes haldol (haloperidol) + anticholinergic / antihistamine do physical activity at the gym?

Yes: The short answer is yes. I might add, that taking alot of anticholinergic medication, i.e. Cogentin/benztropine or artane/trihexylphenadil-can decrease one's ability to perspire, or sweat. As sweating is the body's natural mechanism to cool off, a concern might be that a person could become overheated. Be sure and drink lots of water and be careful not to become overheated. See: hyperpyrexia.

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Does anticholinergic or antihistamine alone relieve bronchoconstriction in asthma? Will doctors prescribe one or another or both with beta 2 agonist?

Does anticholinergic or antihistamine alone relieve bronchoconstriction in asthma? Will doctors prescribe one or another or both with beta 2 agonist?

Anticholinergic: Anticholinergic but not the usual doses of antihistamine relieves bronchoconstriction in some people. It may be used as a combination with a beta 2 agonist as in the case of combivent (albuterol and ipratropium). However persistent asthma should be treated with a controller drug such as inhaled steroid and/or a leukotriene blocker. Using just beta agonist alone on a regular basis may actually make your asthma worse.

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Will benadryl (diphenhydramine) have an effect on a methacholine challenge since its a anticholinergic drug?

Will benadryl (diphenhydramine) have an effect on a methacholine challenge since its a anticholinergic drug?

Possibly: To get the best indication of bronchial hyper reactivity, you should not take any antihistamines for 3 to 7 days before the challenge. Unless, of course, the point is to see if Benadryl (diphenhydramine) will diminish the reactivity. That's why you need to discuss such questions with the physician who ordered the test.

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Do anticholinergic medications like Benadryl (diphenhydramine) have a link with mild cognitive impairment?

Do anticholinergic medications like Benadryl (diphenhydramine) have a link with mild cognitive impairment?

No: Unlikely; Benadryl (diphenhydramine) has drowsy effects, but clears out after few hours. Interestingly can cause paradoxical stimulation as a side effect. A chronic mild cognitive impairment could be something else.

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What are the side effects of using antihistamines?

What are the side effects of using antihistamines?

Few: There are no long term adverse effects from using antihistamines. Short term sides effects are typically from older antihistamines such as Benadryl (diphenhydramine) that can cause drowsiness and delayed reaction time. New generation antihistamines such as claritin, clarinex, zyrtec, xyzal and Allegra are generally very well tolerated. No dependence and few if any drug interactions.

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I wish to know what are the side effects of antihistamines?

I wish to know what are the side effects of antihistamines?

Tiredness: Mostly they cause tiredness but if you have a prostate problem, be careful don't drink and take benedry and don't drive or operate heavy machinery!

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How can we reduce or eliminate the side effects of antihistamines?

How can we reduce or eliminate the side effects of antihistamines?

Try different brands: The side effects of antihistamines (dry mouth, tiredness. Etc) vary from drug to drug. For example Benadryl (diphenhydramine) OTC is more likely to make you sleepy (in fact for some its a safe sleeping pill) whereas the more recent additions to the OTC antihistamine group (eg Claritin) have less sleepiness (but more dry mouth) Each Person reacts differently to these drugs Try some Hope this helps DR Z

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What are the side effects of antihistamines and what can we do about each?

What are the side effects of antihistamines and what can we do about each?

3rd generation AH: Older antihistamines (AH) like Benadryl, (diphenhydramine) Atarax, Periactin caused drowsiness and dry mouth in at least 30% of the people. Weight gain in another potential side effect. Newer antihistamines like Zyrtec, Xyzal causes drowsiness in about 10% of the people 3rd generation AH like Allegra and Claritin are not expected to cause drowsiness in 95% of the people.

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Which effects does antihistamines have on the body?

Many: New generation antihistamines (claritin, zyrtec, (cetirizine) allegra) will decrease itching, runny nose and sneezing associated with allergies. They also help with itching and hives. Older antihistamines do the same, but may also cause side effects like dry mouth, dry eyes, GI upset, fatigue, sleepiness, impaired reaction time, and increased appetite.

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Will taking antihistamines at bedtime reduce its effects the second day?

Antihistamines: At night should not have any effect on how well they work the next day. People don't get desensitized to antihistamines, though a lot think they do. If you are taking Benadryl (diphenhydramine) at bedtime, don't expect it to take care of you the next day though, as it is a short acting medication.

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What are the effects of using antihistamines taken long term for many months?

None: Generally antihistmaines cause short term side effects such as drowsiness.

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Is antihistamine bad for asthma. If not what is the safest antihistamine to take with minimum side effects?

No: Antihistamines are not bad to take if you have asthma, however if you're using them to treat asthma symptoms this is not appropriate. Antihistamines are for itchy, sneezy symptoms secondary to allergies. Asthma medications include albuterol and daily inhaled steroids. Non-sedating antihistamines like Claritn, Zyrtec, and Allegra (fexofenadine) have relatively equal efficacy and safety profiles

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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.

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Can a non drowsy antihistamine that had no side effects that I've noticed hurt you if u take 2 pills in 24hrs instead of 2?

Can a non drowsy antihistamine that had no side effects that I've noticed hurt you if u take 2 pills in 24hrs instead of 2?

No: Which antihistamine? Why using it? Sometimes, for chronic urticaria, cetirizine [Zyrtec] is dosed at 3 a day. The official dose of these is 1 a day. Allegra and claritin are also sometimes used at double or triple dose. It is best if you consult a Dr before you take doses higher than usual.

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Is it possible to get "rebound" side effects from stopping an antihistamine? I've been taking one for 5 months, and have sinus problems since stopping

You probably need it: Rebound to cessation of antihistamines would be unusual, . If you took a combination antihistamine/decongestant, it would be more common. However, you had been taking an antihistamine for 5 months. Had you taken it for a nasal problem? My hunch is that your nasal/sinus problem, for which you had taken the antihistamine in the first place, recurred the moment you stopped it.

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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.

Benadryl (Definition)

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


Dr. Paul Carter
638 Doctors shared insights

Antihistamine (Definition)

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