Alcohol: Postural hypotension associated with diuretic therapy may be enhanced.
Aldesleukin: Enhanced hypotensive effect may occur when aldesleukin and amiloride are used concomitantly.
Anaesthetics, general: Enhanced hypotensive effect may occur when general anaesthetics and amiloride are used concomitantly.
Analgesics: Diuretics increase the risk of nephrotoxicity with NSAIDs. Indometacin and possibly other NSAIDs increase the risk of hyperkalaemia with potassium-sparing diuretics. Indometacin and ketorolac antagonise the diuretic effect.
Antiarrhythmics: The antiarrhythmic activity of quinidine can be opposed by amiloride.
Antidepressants: increased risk of postural hypotension with tricyclics. Enhanced hypotensive effect with monoamine oxidase inhibitors (MAOIs).
Antidiabetic agents: Chlorpropamide increases the risk of hyponatraemia associated with thiazides in combination with potassium sparing diuretics.
Antiepileptics: increased risk of hyponatraemia with carbamazepine.
Antihypertensives: An enhanced hypotensive effect (which can be extreme) can occur with antihypertensives, including ACE inhibitors, angiotensin-II antagonists, calcium channel blockers, beta blockers, alpha blockers (increased risk of first dose hypotension) or hydralazine. With ACE inhibitors and angiotensin-II antagonists there is also an increased risk of hyperkalaemia.
Antipsychotics: Lithium should not be given with diuretics because they reduce its renal clearance and add a high risk of lithium toxicity. Enhanced hypotensive effect may occur when phenothiazines and amiloride are used concomitantly.
Corticosteroids: Fluid retention associated with corticosteroid use may antagonise the diuretic/antihypertensive response.
Dopaminergics: Enhanced hypotensive effect may occur when levodopa and amiloride are used concomitantly.
Hormones and other endocrine drugs: Combined oral contraceptives and oestrogens may antagonise the diuretic effect. There is an increased risk of hyperkalaemia with trilostane.
Immunosuppressants: increased risk of hyperkalaemia with ciclosporin and tacrolimus. Increased risk of nephrotoxicity with concomitant use of ciclosporin and amiloride.
Muscle relaxants: enhanced hypotensive effect with baclofen and tizanidine.
Nitrates: Enhanced hypotensive effect may occur when nitrates and amiloride are used concomitantly.
Potassium conserving agents, potassium supplements: When amiloride is administered concomitantly with potassium conserving agents or potassium supplements, there is an increased risk of hyperkalaemia (see 4.3 Contraindications).
Prostaglandins: Hypotensive effect may be potentiated by alprostadil.
Ulcer-healing agents: Amiloride antagonises the ulcer-healing effect of carbenoxolone.
Laboratory value alterations: Creatinine clearance: Amiloride blocks the tubular secretion of creatinine, leading to falsely high measurements of creatinine clearance.