No guidelines have suggested that Angiotensin Converting Enzyme Inhibitors (ACEI) and Angiotensin Receptor Blockers (ARB) can be given together. Yet in practice, well i should say malpractice, many doctors do prescribe both simultaneously. This is not good at all since recent trials have shown that using both together doubles the risk of hyperkalemia and doubles the level of creatinine and risk of developing ESRD within 6 months of bi therapy.