Abiraterone acetate is a new androgen deprivation therapy, approved by the FDA in 2011 in combination with prednisone for mCRPC (Goldberg and Berrios-Colon 2013). Abiraterone therapy significantly prolongs overall survival and reduces tumor burden in patients with castration-sensitive prostate cancer (Fizazi et al. 2017; James et al. 2017). The median time to reach the maximum plasma concentration of abiraterone is 2 h and has an elimination half-life of 12 h (Thakur et al. 2018).

Abiraterone is a selective and irreversible inhibitor of the 17α-hydroxylase (CYP17) enzyme complex required for androgen biosynthesis. As a result, androgen levels in testicular, adrenal, and prostatic tumor tissues are reduced. CYP17 promotes the formation of dehydroepiandrosterone (DHEA) and androstenedione which are precursors of testosterone (Yamamoto et al. 2018) (Fig. 2). Abiraterone administration inhibits corticosteroid and androgen production, resulting in hypothalamic-pituitary axis (HPA) upregulation. This potentially results in an increase in ACTH levels and consequently increased mineralocorticoid production by the adrenal glands (Thakur et al. 2018). This may result in mineralocorticoid excess syndrome (MES) characterized by a triad of fluid retention, hypertension, and hypokalemia (Yamamoto et al. 2018). To prevent MES, concurrent administration of glucocorticoid is currently adopted in routine practice.

Mechanism of action of abiraterone acetate

Yamamoto et al described 2 cases of severe life-threatening hypokalemia leading to convulsive seizure and severe lethargy associated with abiraterone within 2 weeks and 1 month after starting the treatment respectively (Yamamoto et al. 2018). Torsades de pointes related to Abiraterone-induced hypokalemia have also been observed in two case reports (Lee et al. 2022; Riad et al. 2021). Similar to our case, Rajvanshi et al. also observed quadriplegia secondary to abiraterone-related hypokalemia (Rajvanshi et al. 2019). However, none of the cases described were perioperative.

Hypokalemia is defined as potassium < 3.5 meq/l. It has 4 grades of severity (Clase et al. 2020) (Table 1). Hypokalemia is a known side effect of abiraterone, but severe grade 4 hypokalemia is extremely rare and reported in only 1% of patients (Fizazi et al. 2017). Severe hypokalemia may present as an ascending paralysis, intestinal paralysis, respiratory failure, or cardiac dysrhythmias. However, there is a high degree of interindividual variability, presentation of aphonia is unusual and not being described in the literature.

There is a recommendation for the continuation of antineoplastic urologic medications up to the day of surgery (Pfeifer et al. 2021). However, we observed severe grade 4 hypokalemia in our patient when abiraterone with steroids was continued preoperatively. Prednisolone, usually prescribed with abiraterone itself has mineralocorticoid activity (0.8) which may precipitate mineralocorticoid excess syndrome. It may be preferable to add dexamethasone or eplerenone when glucocorticoid supplementation is insufficient to manage abiraterone-induced hypokalemia (Yamamoto et al. 2018).

With an extensive literature search, we did not find any data on the anesthetic implications of preoperative administration of abiraterone. Meticulous preoperative examination, vigilance, and stringent monitoring of potassium, cortisol, and ACTH levels should be considered in patients on Abiraterone. Drugs causing hypokalemia should be taken into consideration. Further clinical studies are required to determine the risks and benefits of continuing abiraterone preoperatively.