A parenteral formulation of esmolol hydrochloride for use in the treatment of a patient suffering from tachycardia comprising a lyophilized powder consisting of pure esmolol hydrochloride, wherein said powder is reconstituted to obtain a ready-to-use i.v. solution of esmolol hydrochloride at a concentration of 20-100 mg/mL, and said i.v. solution is directly administered to the patient, and further a method of producing a ready-to-use i.v. solution of esmolol hydrochloride by reconstituting a lyophilized powder consisting of pure esmolol hydrochloride with a solvent, characterized in that said solvent is an i.v. solvent devoid of alcohol or a buffer excipient, in an amount necessary to obtain a ready-to-use i.v. solution at a concentration of 20-100 mg/mL, and the ready-to-use i.v. solution containing a parenteral formulation of 20-100 mg/mL pure esmolol hydrochloride in an infusion device or consisting of a parenteral formulation of 20-100 mg/mL pure esmolol hydrochloride, WFI and/or saline solution, devoid of any alcohol or buffer excipients.