What is the recommended workup for a patient with suspected secondary hypertension who is already on spironolactone (aldactone)?

Secondary Hypertension Workup in Patients on Spironolactone

For patients on spironolactone who require evaluation for secondary hypertension, discontinue spironolactone temporarily (if possible) before performing diagnostic testing for primary aldosteronism, as it will interfere with aldosterone-to-renin ratio measurements. 1

Initial Assessment

• Confirm true resistant hypertension by:

  • Verifying proper BP measurement technique
  • Ruling out white coat effect with ambulatory BP monitoring
  • Assessing medication adherence
  • Reviewing current antihypertensive regimen 2, 1

• Screen for clinical clues suggesting secondary causes:

  • Early onset hypertension (<30 years)
  • Resistant hypertension despite optimal therapy
  • Sudden deterioration in previously well-controlled BP
  • Hypertensive urgency or emergency 2, 1

Diagnostic Testing Strategy

First-line Tests (for all patients):

• Basic blood biochemistry (sodium, potassium, eGFR, TSH)
• Urinalysis and urine albumin-to-creatinine ratio
• Renal ultrasound 2, 1

Targeted Testing Based on Suspected Cause:

Suspected Cause	Recommended Screening Test	Special Considerations with Spironolactone
Primary aldosteronism	Aldosterone-to-renin ratio	Discontinue spironolactone 4-6 weeks before testing
Renovascular hypertension	Renal Doppler ultrasound, CT/MR angiography	No direct interference
Pheochromocytoma	24h urinary/plasma metanephrines	No direct interference
Obstructive sleep apnea	Overnight polysomnography	No direct interference
Cushing's syndrome	24h urinary free cortisol, dexamethasone suppression	No direct interference
Thyroid disease	TSH	No direct interference
Hyperparathyroidism	PTH, calcium, phosphate	No direct interference
Coarctation of aorta	Echocardiogram, CT angiogram	No direct interference

Managing Spironolactone During Workup

• Primary aldosteronism testing: Spironolactone must be discontinued 4-6 weeks before testing as it directly interferes with aldosterone-to-renin ratio measurements 1

• Blood pressure management during spironolactone discontinuation:

  • Replace spironolactone with alternative agents that don't interfere with testing
  • Consider calcium channel blockers or alpha-blockers as temporary alternatives 1

• Monitoring during medication changes:

  • Check serum potassium within 1 week of discontinuing spironolactone 3
  • Monitor BP closely as discontinuation may lead to BP elevation 3

Special Considerations

• Medication interactions: Be aware that spironolactone can cause hyperkalemia, especially when combined with ACE inhibitors, ARBs, or potassium supplements 3

• Renal function: Monitor renal function closely, as spironolactone can worsen renal function, particularly in salt-depleted patients 3

• Electrolyte monitoring: Spironolactone can cause hyponatremia, hypomagnesemia, and hypocalcemia in addition to hyperkalemia 3

• Resistant hypertension management: If spironolactone (25-50 mg daily) was effective before workup, consider resuming it after completing diagnostic testing if no specific secondary cause is identified 2, 1

Follow-up After Diagnosis

• For confirmed secondary causes, treat the underlying condition while maintaining BP control
• For resistant hypertension without identifiable secondary cause, consider referral to specialized hypertension centers 2, 1
• Resume spironolactone if previously effective and no contraindications exist 2

Remember that spironolactone is particularly effective for resistant hypertension, with studies showing BP reductions of 21-26/9-12 mmHg when added to existing regimens 4, 5, 6.