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Trade namesAlamast, Alegysal, others
Other namesPemirolast potassium
  • 9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidin-4-one
Clinical data
Drug classMast cell stabilizer[1]
Main usesAllergic conjunctivitis[1]
Side effectsHeadache, runny nose[1]
  • US: C (Risk not ruled out)[2]
Routes of
By mouth, eye drop
External links
US NLMPemirolast
Legal status
  • US: ℞-only
  • In general: ℞ (Prescription only)
Chemical and physical data
Molar mass228.215 g·mol−1
3D model (JSmol)
  • CC1=CC=CN2C1=NC=C(C2=O)C3=NNN=N3
 ☒NcheckY (what is this?)  (verify)

Pemirolast, sold under the brand names Alamast among others, is a medication used to treat allergic conjunctivitis.[1] It is used as an eye drop.[1]

Common side effects include headache and runny nose.[1] Safety in pregnancy and breastfeeding is unclear.[3] It is is a mast cell stabilizer.[1]

Pemirolast was approved for medical use in the United States in 1999.[1] As of 2021 it is not commercially available in the United States.[4]

Medical uses

The combination of levocabastine and pemirolast may be more effective than levocabastine alone.[5]


It may be used as 1 to 2 drops up to 4 times per day.[1]


It has also been studied for the treatment of asthma. Pemirolast has appeared as a possible candidate for SARS-CoV-2 (COVID-19) spike protein disruption and interference. Such results were ascertained by molecular dynamics calculations executed on the Summit supercomputer. By simulating compounds with FDA or similar regulatory approval, the authors found 4 interfacial molecules that could potentially disrupt the SARS-CoV-2 interface with ACE-2 receptors, suggesting that such small molecules could mitigate SARS-CoV-2 infection. The 4 candidate interfacial molecules included pemirolast, isoniazid pyruvate, nitrofurantoin, and eriodictyol.[6]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 "Pemirolast Monograph for Professionals". Retrieved 27 October 2021.
  2. "Pemirolast ophthalmic (Alamast) Use During Pregnancy". 2 September 2020. Retrieved 13 September 2020.
  3. "Pemirolast ophthalmic (Alamast) Use During Pregnancy". Retrieved 27 October 2021.
  4. "Pemirolast Prices and Pemirolast Coupons - GoodRx". GoodRx. Retrieved 27 October 2021.
  5. Castillo M, Scott NW, Mustafa MZ, Mustafa MS, Azuara-Blanco A (2015). "Topical antihistamines and mast cell stabilisers for treating seasonal and perennial allergic conjunctivitis". Cochrane Database Syst Rev. 6 (6): CD009566. doi:10.1002/14651858.CD009566.pub2. hdl:2164/6048. PMID 26028608.CS1 maint: uses authors parameter (link)
  6. Smith, MD, Smith JC (April 2020). "Repurposing Therapeutics for COVID-19: Supercomputer-Based Docking to the SARS-CoV-2 Viral Spike Protein and Viral Spike Protein-Human ACE2 Interface". Preprint: 1–28.

External links