Pharmacokinetics and Metabolism

Absorption of azelastine following ocular administration was relatively low. A study in symptomatic patients receiving one drop of azelastine hydrochloride in each eye two to four times a day (0.06 to 0.12 mg azelastine hydrochloride) demonstrated plasma concentrations of azelastine hydrochloride to generally be between 0.02 and 0.25 ng/mL after 56 days of treatment. Three of nineteen patients had quantifiable amounts of N-desmethyl azelastine that ranged from 0.25–0.87 ng/mL at Day 56.

Based on intravenous and oral administration, the elimination half-life, steady-state volume of distribution and plasma clearance were 22 hours, 14.5 L/kg and 0.5 L/h/kg, respectively. Approximately 75% of an oral dose of radiolabeled azelastine hydrochloride was excreted in the feces with less than 10% as unchanged azelastine. Azelastine hydrochloride is oxidatively metabolized to the principal metabolite, N-desmethyl azelastine, by the cytochrome P450 enzyme system. In-vitro studies in human plasma indicate that the plasma protein binding of azelastine and N-desmethyl azelastine are approximately 88% and 97%, respectively.

Clinical Trials

In a conjunctival antigen challenge study, azelastine hydrochloride was more effective than its vehicle in preventing itching associated with allergic conjunctivitis. Azelastine hydrochloride had a rapid (within 3 minutes) onset of effect and a duration of effect of approximately 8 hours for the prevention of itching.

In environmental studies, adult and pediatric patients with seasonal allergic conjunctivitis were treated with azelastine hydrochloride for two to eight weeks. In these studies, azelastine hydrochloride was more effective than its vehicle in relieving itching associated with allergic conjunctivitis. 

Information for Patients:

To prevent contaminating the dropper tip and solution, care should be taken not to touch any surface, the eyelids, or surrounding areas with the dropper tip of the bottle. Keep bottle tightly closed when not in use. This product is sterile when packaged.

Patients should be advised not to wear a contact lens if their eye is red. Azelastine hydrochloride should not be used to treat contact lens related irritation. The preservative in azelastine hydrochloride, benzalkonium chloride, may be absorbed by soft contact lenses. Patients who wear soft contact lenses and whose eyes are not red, should be instructed to wait at least ten minutes after instilling azelastine hydrochloride before they insert their contact lenses.

Carcinogenesis, Mutagenesis, Impairment of Fertility:

Azelastine hydrochloride administered orally for 24 months was not carcinogenic in rats and mice at doses up to 30 mg/kg/day and 25 mg/kg/day, respectively. Based on a 30 μL drop size, these doses were approximately 25,000 and 21,000 times higher than the maximum recommended ocular human use level of 0.001 mg/kg/day for a 50 kg adult.

Azelastine hydrochloride showed no genotoxic effects in the Ames test, DNA repair test, mouse lymphoma forward mutation assay, mouse micronucleus test, or chromosomal aberration test in rat bone marrow. Reproduction and fertility studies in rats showed no effects on male or female fertility at oral doses of up to 25,000 times the maximum recommended ocular human use level. At 68.6 mg/kg/day (57,000 times the maximum recommended ocular human use level), the duration of the estrous cycle was prolonged and copulatory activity and the number of pregnancies were decreased. The numbers of corpora lutea and implantations were decreased; however, the implantation ratio was not affected.

Pregnancy:

Teratogenic Effects: Pregnancy Category C. Azelastine hydrochloride has been shown to be embryotoxic, fetotoxic, and teratogenic (external and skeletal abnormalities) in mice at an oral dose of 68.6 mg/kg/day (57,000 times the recommended ocular human use level). At an oral dose of 30 mg/kg/day (25,000 times the recommended ocular human use level), delayed ossification (undeveloped metacarpus) and the incidence of 14th rib were increased in rats. At 68.6 mg/kg/day (57,000 times the maximum recommended ocular human use level) azelastine hydrochloride caused resorption and fetotoxic effects in rats. The relevance to humans of these skeletal findings noted at only high drug exposure levels is unknown.

There are no adequate and well-controlled studies in pregnant women. Azelastine hydrochloride should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Nursing Mothers:

It is not known whether azelastine hydrochloride is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when azelastine hydrochloride is administered to a nursing woman.

Pediatric Use:

Safety and effectiveness in pediatric patients below the age of 3 have not been established.

Geriatric Use:

No overall differences in safety or effectiveness have been observed between elderly and younger adult patients.