Puresis contains furosemide 40 mg, a loop diuretic — a strong “water tablet”. It removes excess fluid in heart failure, kidney disease and liver disease, relieving swollen legs and breathlessness. It works within an hour, so it is taken in the morning.
What is Puresis?
Puresis contains furosemide 40 mg, the most widely used loop diuretic. It is a Schedule 3 medicine, and the same ingredient is dispensed as Furosemide, Lasix and Defulide.
Furosemide acts on a specific segment of the kidney tubule — the ascending limb of the loop of Henle, which gives the class its name. There it blocks a transporter that would normally return sodium to the body. The sodium stays in the urine, water follows it, and urine volume rises substantially.
The loop of Henle handles a large share of the kidney’s salt reabsorption, which is why loop diuretics are considerably stronger than thiazides such as the hydrochlorothiazide in Ridaq. A thiazide nudges fluid balance over weeks; furosemide shifts it within hours.
Two practical points follow. It works fast — within about an hour by mouth, with the main effect over in four to six hours. And it works hard — the increase in urination is considerable, and people are routinely unprepared for the first dose.
What is Puresis commonly used for?
Puresis is prescribed to remove excess fluid:
- Heart failure, its commonest use. A weakened heart lets fluid accumulate in the legs, abdomen and lungs; furosemide clears it.
- Oedema from cardiac, renal or hepatic causes — swollen ankles, legs or abdomen.
- Acute pulmonary oedema, fluid on the lungs, given urgently.
- Chronic kidney disease with fluid retention.
- Liver cirrhosis with ascites, usually alongside spironolactone.
- High blood pressure, particularly with reduced kidney function — though thiazides are preferred for uncomplicated hypertension.
What furosemide does extremely well is relieve congestion. Someone breathless from fluid on the lungs improves within hours, and that effect is among the more dramatic in everyday medicine.
What it does not do, in heart failure, is change the course of the illness. The medicines that improve survival are different ones — ACE inhibitors such as enalapril or ARBs, beta blockers, mineralocorticoid antagonists such as spironolactone, and newer agents. Furosemide manages symptoms alongside them.
That distinction matters practically. People naturally prioritise the tablet that makes them feel better and neglect the ones producing no noticeable sensation — which is exactly backwards. Both belong in the regimen.
How Puresis fits into this medicine category
| Group | Examples | Strength and role |
|---|---|---|
| Loop diuretics | Furosemide (Puresis, Lasix, Defulide) | Strongest; fluid overload |
| Thiazide diuretics | Hydrochlorothiazide (Ridaq) | Milder; long-term blood pressure |
| Potassium-sparing | Spironolactone, amiloride | Retains potassium; heart failure, ascites |
| ACE inhibitors / ARBs | Enalapril, losartan | Blood pressure, heart failure, kidney protection |
| Calcium channel blockers | Amlodipine (Ciplavasc) | Blood pressure, angina |
See the heart, blood pressure and circulation medicines hub.
What to check before using Puresis
Take it in the morning. Taken later it will keep you up at night. A second dose, if prescribed, goes early afternoon rather than evening.
Be near a toilet for the first few doses, and plan travel and outings around the timing.
Tell your prescriber or pharmacist if:
- You have kidney or liver disease.
- You have gout. Furosemide raises uric acid and can trigger a flare.
- You have diabetes, where blood sugar control can be affected.
- You have low blood pressure, or feel faint standing up.
- You have an enlarged prostate or difficulty passing urine — a sudden large urine volume can cause retention.
- You are pregnant or breastfeeding.
- You take digoxin — low potassium makes digoxin toxicity more likely; lithium; an aminoglycoside antibiotic; or an anti-inflammatory such as ibuprofen or diclofenac, which blunts its effect and adds kidney risk.
- You take other blood pressure medicines or another diuretic.
Blood tests are part of the treatment, not an optional extra — potassium, sodium and kidney function are checked periodically.
Follow the dispensing label. This page does not set doses.
Possible cautions and when to ask a pharmacist or doctor
Low potassium is the principal risk. Furosemide removes potassium along with sodium. Low potassium causes muscle weakness, cramps and disturbances of heart rhythm, and it is more dangerous in anyone taking digoxin. Potassium supplements or a potassium-sparing diuretic are often prescribed alongside — take them as directed rather than treating them as optional extras.
Dehydration and low blood pressure follow from removing too much fluid: thirst, dry mouth, light-headedness on standing. In hot weather, or during an illness with vomiting or diarrhoea, ask whether to pause the dose.
Weigh yourself daily if you have heart failure — same time each morning, after the toilet, before breakfast. A rise of about 2 kg over two or three days signals fluid returning, usually before swelling or breathlessness appear, and reporting it early often prevents a hospital admission. This is the single most useful thing you can do yourself.
Low sodium causes confusion, headache and nausea, particularly in older adults.
Hearing effects — ringing in the ears or reduced hearing — are uncommon and usually associated with high intravenous amounts, but should be reported.
Do not skip it to avoid the urination. Fluid re-accumulates, and in heart failure that leads to hospital admission. Adjust the timing with your prescriber instead.
Seek medical attention for muscle weakness, cramps or palpitations; marked dizziness or fainting; confusion; very little urine; increasing breathlessness, especially lying flat; rapid weight gain or worsening swelling; severe thirst; hearing changes or ringing in the ears; or yellowing of the skin or eyes.
Related medicine guides
- Browse Heart, Blood Pressure & Circulation Medicines guides
- Read: Ciplavasc used for
- Read: Ridaq used for
Frequently asked questions
What is Puresis 40 mg used for? Removing excess fluid in heart failure, kidney disease and liver disease, and sometimes for high blood pressure. It contains furosemide.
Is it the same as Lasix? Yes. Both are brands of furosemide, as is Defulide.
When should I take it? In the morning. It works within about an hour and will disturb your sleep if taken late in the day.
Why do I need potassium tablets with it? Furosemide removes potassium along with water, and low potassium affects muscles and heart rhythm. The supplement replaces what is lost.
Why should I weigh myself every day? In heart failure, a gain of about 2 kg over two or three days means fluid is returning — usually before you can see or feel it. Report it promptly.
Can I take ibuprofen with it? Check with your doctor. Anti-inflammatories reduce its effect and increase the risk to the kidneys when combined with a diuretic.