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Class: Antiallergic Agents
VA Class: OP300
Chemical Name: 9-Methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2a]pyrimidin-4-one potassium salt
Molecular Formula: C10H7KN6O
CAS Number: 100299-08-9
Brands: Alamast

Medically reviewed by Last updated on Aug 24, 2020.


Mast-cell stabilizer.1

Uses for Pemirolast

Allergic Conjunctivitis

Prevention of ocular itching associated with allergic conjunctivitis.1

Pemirolast Dosage and Administration


Ophthalmic Administration

Apply topically to the eye as an ophthalmic solution.1 Not for injection or oral use.1

Avoid contamination of the solution container.1


Available as pemirolast potassium; dosage expressed in terms of the salt.1

Initiate therapy before and continue throughout pollen season.4 5 6 7

Pediatric Patients

Allergic Conjunctivitis

Children ≥3 years of age: 1 or 2 drops of a 0.1% solution in the affected eye(s) 4 times daily.1

Symptomatic response (i.e., decreased itching) may be evident within a few days following initiation but frequently requires up to 4 weeks of therapy.1 2 3


Allergic Conjunctivitis

1 or 2 drops of a 0.1% solution in the affected eye(s) 4 times daily.1

Symptomatic response (i.e., decreased itching) may be evident within a few days following initiation but frequently requires up to 4 weeks of therapy.1 2 3

Cautions for Pemirolast


  • Known hypersensitivity to pemirolast or any ingredient in the formulation.1


Specific Populations


Category C.1


Distributed into milk in rats; not known whether distributed into human milk.1 Caution if used in nursing women.1

Pediatric Use

Safety and efficacy not established in children <3 years of age.1

Common Adverse Effects

Headache, rhinitis, cold/flu symptoms.1

Interactions for Pemirolast

No formal drug interaction studies to date.8

Pemirolast Pharmacokinetics



Following topical application to both eyes (0.1% solution 4 times daily for 2 weeks), peak plasma concentrations were attained within about 25 minutes, but were substantially lower than those following a single (10 mg) oral dose.1


Elimination Route

10–15% of topical ophthalmic dose excreted unchanged in urine.1


About 4.5 hours.1







  • Suppresses the release of mediators from cells involved in hypersensitivity reactions, including mast cells, and decreases chemotaxis and activation of eosinophils.1

  • Reportedly blocks calcium channels in mast cell membranes.1

Advice to Patients

  • Importance of learning and adhering to proper administration techniques to avoid contamination of the product.1

  • Importance of removing soft contact lenses prior to administration of each dose.1 Delay reinsertion for 10 minutes after administration if eyes are not red; do not wear contact lenses if eye(s) are red.1 Not indicated for contact lens-related irritation.1

  • Importance of reporting any worsening of symptoms or new-onset ocular pain/discomfort.8

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.1

  • Importance of informing patients of other important precautionary information.1 (See Cautions.)


Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Pemirolast Potassium


Dosage Forms


Brand Names





Alamast (with lauralkonium chloride)


AHFS DI Essentials™. © Copyright 2021, Selected Revisions September 1, 2005. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.


1. Santen Incorporated. Alamast (pemirolast potassium) ophthalmic solution prescribing information. Napa, CA; 2000. From Santen web site.

2. Anon. New drugs for allergic conjunctivitis. Med Lett Drugs Ther. 2000; 42:39-40.

3. Schwartz EM, Abelson MB, McGarr PJ et al. A placebo controlled evaluation of the ocular efficacy and safety of 0.1% pemirolast potassium ophthalmic in subjects with acute seasonal allergic conjunctivitis. Invest Ophthalmol Vis Sci. 1998; 39:S66.

4. Ciprandi G, Buscaglia S, Cerqueti PM et al. Drug treatment of allergic conjunctivitis: a review of the evidence. Drugs. 1992; 43:154-76.

5. Morrow GL, Abbott RL. Conjunctivitis. Am Fam Physician. 1998; 57:735-46.

6. Titi MJ. A critical look at ocular allergy drugs. Am Fam Physician. 1996; 53:2637-42.

7. Galindez OA, Kaufman HE. Coping with the itchy-burnies: the management of allergic conjunctivitis. Ophthalmology. 1996; 103:1335-6.

8. Santen, Napa, CA: Personal communication.

a. Alamast (pemirolast potassium) ophthalmic solution prescribing information. In: [database online]. Montvale, NJ: Thomson Healthcare; 2004.