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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
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

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". Archived from the original on 26 January 2021. Retrieved 27 October 2021.
  2. "Pemirolast ophthalmic (Alamast) Use During Pregnancy". 2 September 2020. Archived from the original on 23 November 2020. Retrieved 13 September 2020.
  3. "Pemirolast ophthalmic (Alamast) Use During Pregnancy". Archived from the original on 23 November 2020. Retrieved 27 October 2021.
  4. "Pemirolast Prices and Pemirolast Coupons - GoodRx". GoodRx. Archived from the original on 13 June 2016. 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.{{cite journal}}: 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. Archived from the original on 2020-10-28. Retrieved 2020-12-12.

External links