Losartan

Mechanism

Dual RAAS blockade (ACE-I + ARB). Additive hyperkalaemia, hypotension, and acute kidney injury risk without added benefit.

Symptoms

Weakness, postural dizziness, syncope. Reduced urine output, rising creatinine. Weakness and paraesthesia from hyperkalaemia.

Management

The combination is not prescribed. Choose one: ACE-I if tolerated, ARB if there is a dry cough.

Mechanism

Similar to enalapril + celecoxib. NSAIDs reduce renal blood flow; the ARB (losartan) lowers glomerular pressure. The combination causes acute kidney injury.

Symptoms

Reduced urine output, rising creatinine and potassium, oedema. Symptoms appear earlier in older patients and in chronic kidney disease.

Management

For prolonged celecoxib therapy, check creatinine 2–4 weeks after start, then every 3 months. In older patients and chronic kidney disease, paracetamol is preferable.

Mechanism

Trimethoprim blocks sodium channels via an amiloride-like mechanism, additively with an ARB (losartan) causing hyperkalaemia. In older patients, sudden death risk rises.

Symptoms

Muscle weakness, paraesthesia, slowed pulse, arrhythmias. ECG: peaked T waves, widened QRS. Severe cases progress to cardiac arrest.

Management

During co-trimoxazole therapy, check potassium 3 days after start. In older patients and chronic kidney disease, prefer alternative antibiotics (nitrofurantoin, fosfomycin).

Mechanism

Dual RAAS blockade: ACE-I blocks angiotensin II formation, ARB blocks its receptors. Additive risk of hyperkalaemia, hypotension, and acute kidney injury without additional clinical benefit.

Symptoms

Weakness, dizziness on standing, syncope. Reduced urine output, rising serum creatinine. Weakness and paraesthesia from hyperkalaemia. Symptoms typically appear in the first 1–4 weeks.

Management

The combination is not prescribed. Large trials (ONTARGET, ALTITUDE) showed no benefit and more adverse effects. Choose one agent: ACE-I if tolerated, ARB if there is a dry cough or intolerance.

Mechanism

Losartan (ARB) reduces aldosterone synthesis and angiotensin-dependent constriction of glomerular afferent arterioles. In a volume-depleted patient on a loop diuretic, the first losartan dose can sharply lower glomerular blood flow and trigger acute kidney injury.

Symptoms

Sharp blood pressure drop on the first dose: dizziness, syncope. Reduced urine output, rising creatinine. Weakness and paraesthesia from hyperkalaemia.

Management

The combination is standard in hypertension and heart failure. Before starting losartan, confirm there is no dehydration (after intensive diuretic therapy). Take the first dose in the evening, lying down. Check potassium and creatinine at 1 week.

Mechanism

A thiazide diuretic plus an ARB synergistically lower blood pressure: the thiazide reduces circulating volume, losartan vasodilates by suppressing the RAAS. This is a target combination in hypertension and available as a fixed-dose product (losartan + hydrochlorothiazide).

Symptoms

Excessive blood pressure drop during titration: postural dizziness, syncope. Hypokalaemia and hyponatraemia from the thiazide, plus a mild rise in creatinine, can occur in the first weeks.

Management

The combination is a treatment standard. Doses are individualised, usually starting with losartan 50 mg + hydrochlorothiazide 12.5 mg/day. Check potassium, sodium, and creatinine 2–4 weeks after start, then annually.

Mechanism

NSAIDs reduce renal blood flow via prostaglandin blockade. The ARB (losartan) lowers glomerular pressure. The combination causes acute kidney injury, especially in older patients, chronic kidney disease, and dehydration.

Symptoms

Reduced urine output, rising creatinine and potassium, oedema. Symptoms appear earlier in older patients and in chronic kidney disease.

Management

Avoid prolonged combination. If ibuprofen is needed for a short course, use the minimum effective dose for 5–7 days with pantoprazole cover and creatinine monitoring. For chronic analgesia: paracetamol or celecoxib.

Mechanism

Losartan, like ACE inhibitors, reduces lithium renal clearance via angiotensin blockade of the efferent arteriole. Lithium rises 20–40%. Effect described for all ARBs.

Symptoms

Tremor, nausea, confusion within 1–3 weeks of losartan start.

Management

Check lithium on day 7, day 14 and at one month. Lithium may need a 25–50% reduction.

Mechanism

Losartan (angiotensin II receptor blocker, ARB) suppresses the renin-angiotensin-aldosterone system and reduces aldosterone release. Spironolactone directly blocks aldosterone receptors. Both retain potassium.

Symptoms

Muscle weakness, paraesthesia in the limbs, slowed pulse, arrhythmias. ECG shows peaked T waves and widened QRS. Severe cases progress to cardiac arrest. Symptoms typically appear within 1–2 weeks of starting the combination.

Management

The combination is appropriate in heart failure. Check potassium and creatinine 1 week after start, then monthly. If potassium exceeds 5.5 mmol/L, reduce the dose of one agent; above 6.0 mmol/L, stop one of them.