5 doctors weighed in:

What is the difference between first and second-generation antihistamines?

5 doctors weighed in
Dr. Stephen Kimura
Internal Medicine - Allergy & Immunology
2 doctors agree

In brief: Side effects

The second generation antihistamines were developed to try and decrease the side effects of the first generations.
Many are "purified" first generation antihistamines so they have the active effects without the side effects of drowsiness, sedation, dry mouth etc. They also tend to have longer half lives, meaning they can be taken once or twice a day not every 4 hours.

In brief: Side effects

The second generation antihistamines were developed to try and decrease the side effects of the first generations.
Many are "purified" first generation antihistamines so they have the active effects without the side effects of drowsiness, sedation, dry mouth etc. They also tend to have longer half lives, meaning they can be taken once or twice a day not every 4 hours.
Dr. Stephen Kimura
Dr. Stephen Kimura
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Dr. Manav Singla
Internal Medicine - Allergy & Immunology

In brief: Sleepyness

The first generation antihistamines (benadryl, chlor-trimeton, tavist) are short acting and usually make people sleepy.
Second generation (claritin, zyrtec, allegra, xyzal, (levocetirizine) clarinex) are long acting once a day, and generally do not make people sleepy, or less so.

In brief: Sleepyness

The first generation antihistamines (benadryl, chlor-trimeton, tavist) are short acting and usually make people sleepy.
Second generation (claritin, zyrtec, allegra, xyzal, (levocetirizine) clarinex) are long acting once a day, and generally do not make people sleepy, or less so.
Dr. Manav Singla
Dr. Manav Singla
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Dr. Jack Mutnick
Internal Medicine - Allergy & Immunology

In brief: Antihistamines

1st generation are better antihistamines but have significant drowsiness.
2nd generation do not bind the receptor as well as 1st generation, but they cause much less drowsiness.

In brief: Antihistamines

1st generation are better antihistamines but have significant drowsiness.
2nd generation do not bind the receptor as well as 1st generation, but they cause much less drowsiness.
Dr. Jack Mutnick
Dr. Jack Mutnick
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