This study evaluates if :

1 ) the plasma aldosterone concentration and blood pressure change in response to roxithromycin could be useful for the screening of PA patients carrying a KCNJ5-mutated APA; 2) the change of PAC in response to mutated KCNJ5 channel is truly occurring in KCNJ5-mutated APA.

Aldosterone-producing adenoma (APA) cause primary aldosteronism (PA), the main curable cause of endocrine hypertension, is in up to 66% of all cases investigated with adrenal vein sampling (AVS). Mutations in the KCNJ5 potassium channel involve up to 70% of APA and cause the most florid PA phenotypes. The recent finding that macrolide antibiotics specifically inhibit in vitro the altered function of mutated KCNJ5 channels has opened new horizons for the diagnosis and treatment of APA with KCNJ5 mutations in that it can allow identification and target treatment of PA patients harbouring a mutated APA. Thus, the aim of the present study was to investigate if clarithromycin and roxithromycin, two macrolides that potently blunt mutated Kir3.4 channel function in vitro, affect plasma aldosterone concentration in adrenal vein blood during AVS and in peripheral blood, respectively, in PA patients with a mutated APA.

The investigators designed two proof of concept studies. In study A: consecutive patients with an unambiguous biochemical evidence of PA will be exposed to a single dose of 250 mg clarithromycin during AVS, to assess its effect on the relative aldosterone secretion index (RASI) in adrenal vein blood from the gland with and without APA. In study B: consecutive hypertensive patients submitted to the work-up for hypertension will receive a single oral dose of 150 mg roxithromycin. The experimental endpoints will be the change induced by roxithromycin of plasma aldosterone concentration (PAC) and other steroids, direct active renin concentration (DRC), serum K+, systolic and diastolic blood pressure.

The investigators expect to prove that: i) clarithromycin allows identification of mutated APA before adrenalectomy and sequencing of tumour DNA; ii) the acute changes of PAC, DRC, and blood pressure in peripheral venous blood after roxithromycin can be a proxy for the presence of an APA with somatic mutations.

Inclusion Criteria:

• A signed and dated informed consent form
• A diagnosis of hypertension defined either as:

Use of antihypertensive drug (s) Arterial hypertension: in untreated patients this must be confirmed by daytime ambulatory blood pressure monitoring (ABPM), or home blood pressure monitoring, with blood pressure higher or equal to 135 mmHg for systolic blood pressure and/or higher or equal to 85 mmHg for diastolic blood pressure.

Normal observation of ECG QT interval.

Exclusion Criteria:

• History of allergy/intolerance to any macrolides;
• Refusal of the patient to undergo dynamic testing;
• Refusal of the patient to undergo AVS and/or contraindications to the general anesthesia that is required for laparoscopic adrenalectomy (for objective 2);
• Suspicion of cortisol-aldosterone co-secreting adenoma
• Pregnancy
• Family history of sudden death
• Family history of syncope
• Family history of Long QT syndrome and or torsade de point
• Congenital or drug-induced Long QT syndrome

The decision to share the data will be taken upon completion of the study and publication of the results.