Introduction: Patients with primary aldosteronism (PA) have increased cardiovascular risk and studies have found that medical therapy fails to ameliorate this. This may be due to side effects and limited efficacy of medications at tolerable doses.

Methods: We conducted a retrospective study on 201 patients with PA treated with medical therapy (spironolactone, eplerenone or amiloride) for PA from 2000-2020 at two tertiary centres. Patients were assessed for efficacy to achieve clinical and biochemical control, and for side effects.

Results: 53.7% of patients achieved blood pressure <140/90mmHg, 44.6% achieved potassium ≥4.3mmol/L, 63.2% achieved renin >1ng/ml/hr, and only 24.6% achieved all three. Concordance of biochemical control using potassium and renin levels was 49%. 45.3% of patients experienced side effects, with 8.5% switching to another medication, 18.9% decreasing dose, and 10.0% stopping medications altogether. Risk factors for side effects were spironolactone use, dose ≥50mg, duration of treatment ≥1year, male gender and unilateral PA. Patients with unilateral PA, compared to bilateral PA, used higher median doses of spironolactone, 75mg vs 50mg, P<0.001, but more had persistent hypokalemia, 20.5% vs 6.4%, P=0.007. 44 patients with unilateral PA underwent surgery after initial medical therapy, which further improved systolic and diastolic BP, from 142 to 134mmHg, P<0.001, and from 85 to 79mmHg, P<0.001, respectively.

Conclusion: Dose-dependent side effects limit the efficacy of medical therapy in PA. Future prospective studies should assess the best monitoring strategy for biochemical control during long-term medical therapy. In patients with unilateral PA, surgery remains a better option compared to life-long medications.