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Table 3A Pharmacokinetics and Pharmacodynamics of Oral H1 Antihistamines Differ in Healthy Young Adults

From: H1 Antihistamines: Current Status and Future Directions

H1 Antihistamine (Metabolite)

Time to Maximum Plasma Concentration (tmax, h) After a Single Dose

Terminal Elimination Half-life (t1/2, h)

Clinically Relevant Drug/Drug Interactions*

Onset/Duration of Action,** h

First generation

    

   Chlorpheniramine‡

2.8 ± 0.8

27.9 ± 8.7

Possible

3/24

   Diphenhydramine‡

1.7 ± 1.0

9.2 ± 2.5

Possible

2/12

   Doxepin‡

2

13

Possible

n/a

   Hydroxyzine‡

2.1 ± 0.4

20.0 ± 4.1

Possible

2/24

Second generation

    

   Cetirizine

1.0 ± 0.5

6.5-10

Unlikely

1/≥24

   Desloratadine

1-3

27

Unlikely

2/≥24

   Ebastine (carebastine)

(2.6-5.7)

(10.3-19.3)

n/a

2/≥24

   Fexofenadine

2.6

14.4

Unlikely

2/24

   Levocetirizine

0.8 ± 0.5

7 ± 1.5

Unlikely

1/≥24

   Loratadine (descarboethoxyloratadine)

1.2 ± 0.3 (1.5 ± 0.7)

7.8 ± 4.2 (24 ± 9.8)

Unlikely

2/24

   Mizolastine

1.5

12.9

n/a

1/24

   Rupatadine

0.75-1.0

6 (4.3-13.0)

Possible

2/24

  1. Results are expressed as mean ± SD, unless otherwise indicated.
  2. *Clinically relevant drug-drug interactions are unlikely with most of the second-generation H1 antihistamines.
  3. **Onset/duration of action is based on wheal and flare studies.
  4. ‡Five or 6 decades ago when many of the first-generation H1 antihistamines were introduced, pharmacokinetic and pharmacodynamic studies were not required by regulatory agencies. They have subsequently been performed for some of these drugs. Empirical dosage regimens persist; for example, the manufacturers' recommended diphenhydramine dose for allergic rhinitis is 25 to 50 mg every 4 to 6 hours, and the diphenhydramine dose for insomnia is 25 to 50 mg at bedtime. The use of sustained-action formulations persists, despite the long terminal elimination half-life values identified for medications such as chlorpheniramine.
  5. §Intranasal and ophthalmic H1 antihistamines: tmax, t1/2, and drug-drug interactions were determined after oral administration.
  6. ||Intranasal and ophthalmic H1 antihistamine formulations: onset and duration of action is based on usual adult dose of 1 to 2 sprays in each nostril or 1 drop in each eye.
  7. n/a indicates information not available or incomplete.
  8. Adapted from Simons [2].
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World Allergy Organization Journal

ISSN: 1939-4551

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