Etripamil NS addresses an unmet medical need since there are currently no fast-acting products available for patient self-administered treatment of episodes of PSVT. The only currently available acute pharmacological therapy is IV treatment with adenosine or calcium channel blockers administered in a hospital or medically supervised environment. A self-administered product for PSVT would give patients the option to safely terminate acute episodes of PSVT without the need for a hospital visit and potential admission. An episodic treatment option may also allow selected patients to discontinue chronic prophylactic therapy with Class I, II (e.g., beta-blockers), III, and/or IV (e.g., calcium channel blockers) antiarrhythmic agents, thus avoiding the side effects and quality of life implications associated with these medications. Furthermore, patients weighing the risks of bridging therapy and an invasive catheter ablation procedure to address their PSVT would have the opportunity to consider episodic management with etripamil NS as a viable alternative treatment option.~The potential risks of study participation include those associated with exposure to etripamil NS. The side effect profile appears to be consistent with its expected pharmacology as a short-acting structural analog of verapamil, as well as with its delivery as moderately low pH nasal spray formulation. The most frequently reported (≥5% of subjects across all studies) AEs determined by the investigator to be possibly, probably, or definitely related to etripamil NS include headache, increased lacrimation, epistaxis, nasal congestion, nasal discomfort, rhinorrhea, sneezing and throat irritation.~Potential AEs, which have been rare or not observed in studies to date, include other cardiac arrhythmias, or AEs associated with drops in blood pressure (syncope, symptomatic hypotension).~The primary benefit of this study is that patients may be able to safely and rapidly terminate acute episodes of PSVT without the need for a hospital visit to receive IV medication. Patients may also be able to discontinue chronic prophylactic therapies they are taking for PSVT. Patients who are waiting for, ineligible, or unwilling to undergo ablation procedures may have an option for at-home treatment of their PSVT episodes.
This Open Label Extension study will enable eligible patients with Paroxysmal Supraventricular Tachycardia (PSVT) who have previously participated in a Milestone Pharmaceuticals clinical trial of etripamil NS for PSVT, to access continued treatment with etripamil NS, Patients who experienced any significant safety issues during participation period in a previous clinical trial of etripamil NS, as per Investigator's assessment , are excluded. This study will be conducted by Investigators who previously participated in a Milestone Pharmaceuticals clinical trial and are trained on the use of etripamil NS.