The Use of Captopril—Angiotensin Converting Enzyme (ACE) Inhibitor for Cystinuria During COVID-19 Pandemic

Cystinuria is rare condition affecting around 1:2000 people in United Kingdom but is a chronic condition and presents with recurrent urolithiasis requiring multiple surgical interventions. Studies in adult has demonstrated higher prevalence of hypertension, and renal impairment. Apart from increase fluid intake, alkalinisation of urine and lower salt intake, thiols medications are important second line preventative strategies. There has been issues with supply of both D-Penicillamine and tiopronin and captopril is an easily available drug. Captopril, is the first angiotensin-converting enzyme (ACE) inhibitors in the market and is the only ACE inhibitors that has sulfhydryl ligand that forms bond with cystine. Cystine-Captopril disulphide is 200 times more soluble than cystine and thus prevent stone formation. Captopril has demonstrated to improve blood pressure and protect renal function. Hence it could be used in patients with cystinuria and other comorbidities.¹

It has been suggested that use of ACE inhibitors may exacerbate symptoms in COVID-19 patients and have led to controversies.² The angiotensin-converting enzyme 2, an enzyme that physiologically counters the renin-angiotensin-aldosterone system activation but also functions as a receptor for COVID-19 virus and the COVID-19 S protein binds strongly to the ACE2 receptor.³ Guan et al reported hypertension and diabetes as most common comorbidities in patents admitted with COVID-19 infection, however, treatment with ACE inhibitors was not evaluated separately.⁴ A recent paper reported that acute cardiac injury and heart failure in addition to the acute lung injury may be responsible for severe illness with a high mortality. Interestingly, mortality rate was almost similar in patients with or without history of hypertension.⁵ A sudden withdrawal of ACE inhibitors has been discouraged as this action may result in clinical instability. At present there is scarce data to support any change in practice.

Until further data are available, we should continue captopril to treat stone disease associated with cystinuria. This position is in line with other association and society guidance (Renal Association, UK and European Society of Cardiology).