Pharmacokinetics of cetirizine in tear fluid after a single oral dose

Antihistamines (histamine H(1) receptor antagonists) are effective and convenient drugs for the treatment of allergic conjunctivitis. Because of the short duration of action generally observed for drugs administered topically to the eye, the oral route is often preferred. However, the presence of a selective barrier between blood and ocular tissues, the so-called blood-ocular barrier, does not allow a priori assessment of the most suitable dosage for ocular therapy.