Indications
Chalk, used in medicines as prepared or precipitated chalk, is purified calcium carbonate. It is used as an antacid to relieve heartburn, acid indigestion and upset stomach, and in some antidiarrhoeal mixtures (often with kaolin) to help firm up loose stools. It is also used as a calcium source and as an inactive filler in tablets and toothpastes. Some antidiarrhoeal powders containing chalk are made for animals; those must be used only as directed for animals.
How It Works
Calcium carbonate reacts with stomach acid and neutralises it, which relieves burning pain and indigestion. In diarrhoea mixtures it acts as a mild adsorbent and astringent, helping to bind fluid and irritants in the gut and to thicken stools. Some of the calcium is absorbed into the body.
Dosage and Administration
Chalk is usually part of a combination product. Use it as directed on the label or by your doctor or veterinarian. As an antacid, adults usually take it when symptoms occur or after meals and at bedtime, without exceeding the maximum daily amount on the label. For diarrhoea, also drink plenty of fluids or oral rehydration solution to replace lost water and salts.
Interactions
Chalk can reduce the absorption of many medicines, including Tetracyclines, Ciprofloxacin and other quinolones, Iron, Levothyroxine, Digoxin and bisphosphonates. Take other medicines at least 2 hours before or 4 hours after. Large amounts with milk or calcium supplements can raise blood calcium.
Contraindications
Do not use if you have high blood calcium, kidney stones caused by calcium, severe kidney disease, or are allergic to any ingredient. Antidiarrhoeal mixtures should not be used for bloody diarrhoea, high fever or suspected bowel blockage.
Side Effects
Constipation, wind and belching are the most common side effects. Long-term use of large amounts may cause high blood calcium, kidney stones or acid rebound.
Get urgent medical help if you have severe stomach pain, black or bloody stools, vomiting blood, confusion, extreme thirst or weakness, or signs of dehydration such as very little urine with diarrhoea.
Pregnancy and Lactation
Calcium carbonate antacids are commonly used for heartburn in pregnancy and are considered safe in usual doses. They are also suitable while breastfeeding. Do not exceed the label dose without medical advice.
Precautions and Warnings
Do not use antacids for more than 2 weeks without seeing a doctor, as ongoing symptoms may need investigation. In children with diarrhoea, oral rehydration is the main treatment. Use with caution in kidney disease. Do not use in children unless advised.
Overdose
Large amounts can cause constipation, nausea, vomiting, high blood calcium (confusion, weakness, thirst) and kidney problems. Seek medical advice if too much is taken.
Therapeutic Class
Antacid and adsorbent antidiarrhoeal (calcium carbonate); pharmaceutical excipient.
Storage
Store below 30°C in a dry place, away from light and out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.