ENO: Uses, How It Works, Side Effects
Also known as: Eno fruit salt, Eno powder, Eno sachet, Eno antacid, Eno regular, Sodium bicarbonate citric acid effervescent powder
ENO is an effervescent antacid powder, used for short-term relief of heartburn, acid indigestion and a sour stomach. It contains sodium bicarbonate, which neutralises stomach acid, and citric acid, which makes the powder fizz in water. It contains a lot of sodium, so people on a low-salt diet need to ask a doctor first.
- Active ingredient
- Sodium bicarbonate VERIFY on pack + Citric acid VERIFY on pack
- Type of medicine
- Antacids
- Used for
- Acidity and acid reflux
- Starts working in
- Within minutes, because it neutralises acid already in the stomach
- Effect lasts
- A few hours, so symptoms can return
- With or without food
- Taken dissolved in water, usually with or after meals; follow the label or your doctor's advice
- Alcohol
- Alcohol can irritate the stomach and make symptoms worse
- Pregnancy
- Ask a doctor or pharmacist first; the sodium content is higher than in many antacids
- Habit-forming
- No
- Made by
- VERIFY on pack
Pharmacist review in progress. This page is based on the sources listed below and is being checked by our registered pharmacist.
On this page
What is ENO used for?
ENO is used for short-term relief of symptoms caused by too much stomach acid. Check the pack for the uses printed on it.
- Relieving heartburn and acid indigestion (acidity)
- Relieving a sour stomach or upset stomach linked to acid
How does ENO work?
Sodium bicarbonate reacts with stomach acid to form water, salt and carbon dioxide gas, which makes the stomach contents less acidic and can cause burping. Citric acid reacts with bicarbonate in water, which causes the fizz.
What happens in your body after you take it
You dissolve the powder in water
The powder is stirred into water and fizzes as citric acid and sodium bicarbonate react. You drink it once the fizzing settles.
It meets stomach acid
The remaining sodium bicarbonate reacts with acid in the stomach and turns it into water, salt and carbon dioxide.
Acid falls, gas comes up
The acid level in the stomach falls and the burning feeling eases. The carbon dioxide gas can make you burp.
The effect wears off
Stomach acid keeps being made, so relief lasts only a few hours. The sodium is absorbed and the kidneys remove the extra.
How to take ENO
Follow the label or your doctor's advice. ENO is meant for short-term relief, and the amount depends on the pack and your age.
- Dissolve the powder in the amount of water stated on the pack and drink it after the fizzing settles.
- It is usually taken with or after meals or when symptoms start.
- Do not use the maximum amount for more than 2 weeks unless a doctor advises.
- Leave a gap of 2 to 4 hours between ENO and other medicines.
- Do not give it to a child without checking the pack or asking a doctor.
Side effects of ENO
ENO usually causes few side effects when taken occasionally at the amount on the label.
Uncommon or mild
- Burping or wind
- Bloating or stomach cramps
- Thirst
Rare but serious: get medical help
- Swelling of the face, lips, tongue or throat, or difficulty breathing (a severe allergic reaction). Get medical help immediately
- Severe stomach pain after taking it
- Swelling of the legs or breathlessness (too much sodium, especially with heart or kidney disease)
- Muscle twitching, confusion or weakness with repeated use (a sign of salt imbalance)
Who should be careful
ENO is not suitable for everyone, and long-lasting symptoms need a doctor.
- Low-salt diet, high blood pressure, heart failure or kidney disease: ask a doctor first, because it contains sodium
- Other medicines: antacids can change how they are absorbed, so ask a pharmacist if you take prescription medicines
- Heartburn most days, or symptoms for more than 2 weeks, need a doctor's check
- Difficulty swallowing, repeated vomiting, black stools or weight loss without trying: see a doctor
- Pregnancy and breastfeeding: ask a doctor or pharmacist first
- Do not use it to treat pain in the chest: chest pain can be a heart problem and needs urgent medical help
Medicines and things that interact with ENO
Antacids can change how well other medicines are absorbed. Tell your doctor or pharmacist about everything you take.
- Leave a gap of 2 to 4 hours between ENO and other medicines, as the NHS advises
- Some antibiotics, iron, thyroid tablets and some heart medicines can be affected; ask a pharmacist how to space them
- Large amounts of calcium or milk products with sodium bicarbonate, taken often, can cause a condition called milk-alkali syndrome
If someone takes too much
Taking much more than the label says can cause thirst, stomach cramps, vomiting and, with repeated use, a salt and acid imbalance. If someone has taken much more than the label advises, or feels unwell, call 112 or go to the nearest hospital and take the pack with you.
Storage
Store in a cool, dry place with the pack tightly closed, because moisture makes the powder fizz early. Keep out of the reach of children and do not use after the expiry date. Check the pack for the exact storage instructions.
Regulatory status in India
Approved for sale in India. Sodium bicarbonate with citric acid was not found on the CDSCO list of medicines banned under section 26A (checked in the extracted list text). The CDSCO list does ban a combination of sodium bicarbonate with alginic acid, aluminium hydroxide, magnesium hydroxide and dimethicone, so the pack composition must be checked.
Other brands with the same medicine
Other brands sell effervescent antacid powders made of sodium bicarbonate, but amounts and extra ingredients differ. Check the label before switching, and ask a pharmacist if unsure.
Other strengths and forms
ENO is sold as sachets, bottles of powder and in different flavours, and the amount of each ingredient can differ. Check the pack for the contents of the one you have.
Common questions
What is ENO used for?
ENO is used for short-term relief of heartburn, acid indigestion and a sour stomach. Its sodium bicarbonate neutralises stomach acid. It does not treat the cause of repeated acidity, which needs a doctor's check.
How long does ENO take to work?
It works within minutes because it neutralises acid already in the stomach. The effect lasts only a few hours, so symptoms can return. If you need it most days, see a doctor instead of taking more.
Can I take ENO every day?
ENO is meant for occasional, short-term relief. Labels for sodium bicarbonate say to stop and ask a doctor if symptoms last more than 2 weeks. It also contains sodium, which matters for people with high blood pressure, heart or kidney problems.
Is ENO safe in pregnancy?
Ask a doctor or pharmacist before using it in pregnancy or while breastfeeding. Heartburn is common in pregnancy, and the sodium content of ENO is higher than in many other antacids, so a doctor can suggest what suits you.
Should I use ENO for chest pain?
No. Chest pain can come from the heart rather than from acid. If you have chest pain, pain spreading to the arm or jaw, sweating or breathlessness, call 112 or go to the nearest hospital instead of taking an antacid.
Sources
- Sodium bicarbonate antacid tablets: OTC drug label (updated 12/2023). DailyMed, US National Library of Medicine
- Antacids. NHS (UK)
- List of drugs prohibited for manufacture and sale through gazette notifications under section 26A of the Drugs & Cosmetics Act 1940. Central Drugs Standard Control Organisation (CDSCO)
- ATC/DDD Index: A02AH antacids with sodium bicarbonate. WHO Collaborating Centre for Drug Statistics Methodology