Milestone Pharmaceuticals is a small biopharmaceutical company focused on cardiovascular medicines. Its sole commercial product is CARDAMYST (etripamil nasal spray), FDA-approved in December 2025 for adults to self-administer during acute episodes of paroxysmal supraventricular tachycardia (PSVT), a condition where the heart suddenly beats abnormally fast. CARDAMYST is the first and only therapy patients can self-administer at home to terminate a PSVT episode, without going to the emergency department. Etripamil is a rapid-onset calcium channel blocker that absorbs through the nasal lining into the bloodstream in under 10 minutes, mimicking IV drug speed without requiring medical supervision. Milestone sells CARDAMYST by prescription through retail pharmacies, targeting cardiologists and electrophysiologists through a field sales force of roughly 60 representatives. Revenue is driven by the number of prescribing physicians, patients prescribed the drug, and per-patient utilization. Milestone does not manufacture in-house, relying entirely on contract manufacturers. Beyond PSVT, Milestone is developing etripamil for atrial fibrillation with rapid ventricular rate (AFib-RVR), where a Phase 2 study showed etripamil reduced ventricular rate by roughly 30 bpm versus placebo within about 13 minutes. A single Phase 3 trial of approximately 150 patients would be required for approval. Internationally, Milestone licenses rights to regional partners rather than building its own infrastructure — Corxel holds China rights, and a marketing authorization application was submitted to the European Medicines Agency in November 2025.