The case is presented of a 56 year-old man with a history of squamous cell carcinoma of the penis, who underwent elective surgery of partial penectomy with remodelling. He had a clinical history of secondary clinical hypothyroidism and dyslipidaemia, with no medical history of allergies, or previous surgeries. There were no complications during the partial penectomy surgery. During the procedure intravenous fentanyl, bupivacaine, and midazolam were administered without complications. In the immediate postoperative period and after administering naloxone 0.2 mg, the patient had a mixed respiratory failure, tachycardia, tachypnoea, and then severe bradycardia that progressed to distributive shock, requiring vasopressor and mechanical ventilatory support. Chest radiography and fibrobronchoscopy were performed with findings suggestive of non-cardiogenic pulmonary oedema and generalised bleeding at bronchial tree, lobar, segmental and sub-segmental divisions bilaterally, respectively. The autoimmune profile, the haemosiderophage index of 7% in the bronchioloalveolar lavage, and cardiac enzymes were normal. There were no changes in the electrocardiograph, but the transthoracic ultrasound showed moderate pulmonary hypertension with mild overload of the right ventricle. After management with vasopressors and ventilatory support, there was a successful resolution of the pulmonary oedema, confirmed by chest radiography one month after admission. The Naranjo scale was applied retrospectively, with a score of 5 that suggested a probable relationship of the event with the drug in question. Although naloxone is considered a safe drug with few complications, the indications have to be precise and well documented, since severe complications with non-cardiogenic pulmonary oedema may occur.