Objectives This study aimed to develop a liquid oral formulation containing losartan potassium, an angiotensin II receptor antagonist drug used for its antihypertensive activity, and to perform a preliminary stability assessment under different temperatures and packages to ensure paediatric therapeutic adherence and facilitate the hospital routine.

Methods A syrup containing losartan potassium (1.0 and 2.5 mg/mL) (excipients: potassium sorbate, sucrose (85%), water, citric acid and raspberry flavouring) was prepared. The packaging was carried out in amber polyethylene terephthalate (PET) and amber glass bottles (in triplicate) under the following conditions: (a) room temperature (15–30°C); (b) refrigeration (2–8°C); and (c) oven temperature (40°C) for 28 days. An analytical method by high performance liquid chromatography using a reverse-phase column was also developed and validated for quantitative determination of the drug in the formulations.

Results The analytical method showed satisfactory linearity, detection and quantification limits, precision, accuracy and robustness. Samples at room temperature maintained content values between 90% and 110% for 7 days, while those stored under refrigeration maintained a homogeneous appearance and content between 90% and 110% for a period of 21 days. Values of pH stayed in a narrow range. Viscosity results were between 40.1 and 49.2 centipoise (cp) for glass bottles and 42.4 and 54.7 cp for PET bottles.

Conclusions A simple and economical losartan potassium liquid formulation was produced and was shown to be stable under refrigeration for 21 days in both PET and glass packages.