Background There has been debate on the use of angiotensin-converting enzyme-2 (ACE2) expression mediating pharmacotherapy in COVID-19 infected patients. Although it has been suggested that these... Show moreBackground There has been debate on the use of angiotensin-converting enzyme-2 (ACE2) expression mediating pharmacotherapy in COVID-19 infected patients. Although it has been suggested that these drugs might lead to a higher susceptibility and severity of COVID-19 infection, experimental data suggest these agents may reduce acute lung injury via blocking angiotensin-II-mediated pulmonary permeability, inflammation and fibrosis. Methods A systematic literature search was performed to answer the question: What is the effect of medications that influence ACE2 expression (ACE inhibitors (ACEIs), angiotensin receptor blockers (ARBs), nonsteroidal anti-inflammatory drugs (NSAIDs) and thiazolidinediones) on the outcomes of COVID-19? Relevant outcome measures were mortality (crucial), hospital admission, length of stay, thromboembolic complications (pulmonary embolism, stroke, transient ischaemic attack), need for mechanical ventilation, acute kidney injury and use of renal replacement therapy. Medline and Embase databases were searched with relevant search terms until 24 June 2020. After systematic analysis, nine studies were included. Results The results were described for two different groups, an overall group in which all users were compared with non-users and a group in which only hypertensive patients were included. Within each group a distinction was made between results for ACEI/ARB use, ACEI use, ARB use, NSAID use and thiazolidinedione use. None of the studies demonstrated increased mortality in the two groups. Furthermore, none of the studies showed an effect on other outcome measures in COVID-19, such as ICU admission, length of hospital stay, thromboembolic complications, need for mechanical ventilation, acute kidney failure or need for renal replacement therapy. However, the level of evidence of all studies varied from 'moderate' to 'very low', according to the GRADE methodology. Conclusion Analysis of the literature demonstrated that there was insufficient evidence to answer our objective on the effect of ACE2 expression mediating pharmacotherapy on outcome in COVID-19 patients, especially due to the low scientific quality of the described studies. Randomised controlled studies are needed to answer this question. Show less