Bender, Ph D, of National Jewish Medical and Research Center in Denver."The first-generation antihistamines are more sedating, but the distinction isn't as black-and-white as the marketing of the newer products may lead you to believe. You may have taken antihistamines in the past and found it hard to concentrate or stay awake.For many people, sedating antihistamines, also called old, classic, or first-generation antihistamines, cause sleepiness, grogginess, and slow reaction time.Sold over the counter (OTC), they are less expensive than prescription nonsedating antihistamines. Nonsedating antihistamines, also called new, or second-generation antihistamines, are just as effective against nasal allergy symptoms as older medications. They make you less sleepy and groggy, and are less likely to cause problems with increased eye pressure, which may worsen glaucoma symptoms.Another advantage of the newer antihistamines is that they're available in time-release versions.Your access to the NCBI website at gov has been temporarily blocked due to a possible misuse/abuse situation involving your site.
The newer antihistamines are available only by prescription.
They may interfere with coordination and cloud your concentration.
Many sedating antihistamines do not require a doctor's prescription.
Antihistamines are classified into two groups – the first-generation (“sedating”) and second-generation (“non-sedating”).
Sedating antihistamines cause sedation as they are highly lipid soluble and readily cross the blood brain barrier.