Pemirolast is an antiallergic pharmaceutical compound belonging to the mast-cell stabilizer class. For pharmaceutical use, the active ingredient is commonly supplied as Pemirolast Potassium, the potassium salt of pemirolast. It is associated with inhibition of antigen-mediated mediator release from mast cells and has been used in pharmaceutical products for allergic conditions.
The official Japanese Pharmacopoeia recognizes Pemirolast Potassium as Monopotassium 5-(9-methyl-4-oxo-4H-pyrido[1,2-a]pyrimidin-3-yl)-1H-tetrazol-1-ide. Its molecular formula is C10H7KN6O and molecular weight is 266.30 g/mol. The official CAS number is 100299-08-9.
Pemirolast Potassium occurs as a light yellow crystalline powder. According to the Japanese Pharmacopoeia, it is freely soluble in water, slightly soluble in methanol and very slightly soluble in ethanol (99.5). It also dissolves in potassium hydroxide TS. Its reported melting point is approximately 322°C with decomposition.
The physical and chemical properties make the exact salt form important when preparing pharmaceutical API documentation. Pemirolast free base and Pemirolast Potassium should not be treated as interchangeable substances because their molecular formula, molecular weight and CAS numbers differ.
The Japanese Pharmacopoeia provides multiple identification procedures for Pemirolast Potassium. Identification includes UV-visible spectrophotometry, infrared absorption spectrophotometry and a qualitative test confirming the presence of potassium.
For UV identification, the sample spectrum is compared with the reference spectrum. IR identification is performed using the potassium bromide disk method. The substance must also respond to the qualitative test for potassium salt.
Pemirolast Potassium is required to contain 98.5% to 101.0% of pemirolast potassium, calculated on the anhydrous basis. The official assay is performed by liquid chromatography, using UV detection at 260 nm. The JP method uses an octadecylsilanized silica-gel column and a mobile phase consisting of water, methanol and acetic acid.
This makes the 98.5–101.0% range an appropriate verified value for your CMS assay field.
The Japanese Pharmacopoeia controls related substances by liquid chromatography. The sample is compared with a diluted pemirolast standard solution. The area of each peak other than pemirolast must not be greater than the pemirolast peak in the standard solution. Based on the monograph's dilution scheme, this corresponds to an individual related-substance limit of approximately NMT 0.10%.
The monograph does not provide a separate numerical total impurities limit. Therefore, the CMS should not incorrectly state a total impurity limit such as 1.0% or 0.5%.
Water content is controlled by Karl Fischer coulometric titration, with a requirement of NMT 0.5%. This means the CMS should use the Water Content field rather than assigning the same value to Loss on Drying.
Heavy metals are controlled by the Japanese Pharmacopoeia Method 2, using a lead standard corresponding to NMT 20 ppm.
Pemirolast Potassium requires controlled synthesis, purification and crystallization to obtain the required chemical purity and physical characteristics. Quality control should include chromatographic assay, related-substance testing, water determination, elemental/heavy-metal control and identity testing.
The official JP reference standard documentation confirms that the Pemirolast Potassium reference standard is used for identification and LC assay and is hygroscopic under elevated relative humidity.
Pemirolast Potassium has been used as an antiallergic pharmaceutical ingredient, particularly in ophthalmic and oral pharmaceutical preparations. The Japanese Pharmacopoeia includes monographs for Pemirolast Potassium Ophthalmic Solution, Pemirolast Potassium Tablets and Pemirolast Potassium for Syrup, in addition to the API monograph.
For pharmaceutical manufacturing and API sourcing, the exact form should therefore be stated as Pemirolast Potassium rather than simply Pemirolast whenever the potassium salt is being supplied.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Heavy Metals | NMT 20 ppm |
| Individual Impurity | NMT 0.10% |
| Water Content | NMT 0.5% |
| Melting Point | About 322°C |