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Calcium carbonate antacid

Updated 2 Feb 2023 | Indigestion remedies

Drugs List

  • calcium carbonate 500mg chewable tablet
  • RENNIE ORANGE chewable tablet
  • Therapeutic Indications


    Flatulent dyspepsia


    Not all brands are licensed for all indications.

    Doses vary between brands, and so the specific manufacturers' guidelines should be followed.


    One or two tablets as required up to a maximum of 16 tablets a day. A maximum of 7 tablets a day is recommended in pregnant women.


    No dosage adjustment necessary (see 'Dosage; Adults' section)


    Not all presentations are licensed for all age groups.

    Children under 6 years
    Contraindicated in children under 6 years.

    Children 6-12 years
    One tablet up to a maximum of 4 tablets a day.

    Children aged 12 years and over
    No dosage adjustment is necessary ( see 'Dosage; Adults' section )

    Patients with Renal Impairment

    Contraindicated in patients with severe renal impairment.

    Use with caution in patients with renal impairment. Monitor calcium and phosphate levels regularly.

    Prolonged excessive ingestion of calcium carbonate may lead to hypercalcaemia and milk-alkali syndrome especially in patients with renal insufficiency.



    Severe renal function (see 'Dosage; Renal Impairment' section)

    Children under 6 years


    Severe hypercalciuria



    Precautions and Warnings

    Children aged 6 -12 years (see 'Dosage; Children' section)

    Use with caution in patients with sarcoidosis due to the risk of increased metabolism of vitamin D to its active form. Serum and urinary calcium should be monitored in these patients.

    Patients with mild to moderate renal failure, mild hypercalciuria or on long-term treatment should be supervised carefully. Periodic checks of plasma calcium levels and urinary calcium excretion should be made in these patients.

    If necessary, reduce dose or stop treatment temporarily in mild hypercalciuria, when urinary calcium exceeds 7.5mmol/24hours in adults or exceeds 0.12-0.15mmol/kg/24 hours in children.

    May induce alkalosis and rebound acid hypersecretion.

    Long term use and high doses may cause hypercalcaemia and precipitate milk-alkali syndrome. This also increases the risk of formation of renal calculi.

    Some formulations contain sucrose and glucose. Use with caution in patients with glucose-galactose malabsorption syndrome and hereditary fructose intolerance.

    Prolonged use should be avoided. If symptoms persist, medical advice should be sought.

    Some brands contain Ponceau (E124) that may cause allergic reactions.

    Pregnancy and Lactation


    Calcium containing antacids are generally considered safe in pregnancy. Only about 15-30% of oral calcium carbonate is absorbed from calcium containing antacids. In patients with normal kidney function there is no danger of hypercalcaemia with normal therapeutic use. High intake of calcium carbonate antacids have however been associated with (life-threatening) milk-alkali syndrome during pregnancy (Schaefer, 2007). The unrestricted and long term use of antacids during pregnancy should be avoided.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14-17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Antacids as a group, are generally not considered to cause adverse effects in breastfed infants (LactMed). Calcium carbonate is only absorbed to a limited extent following oral administration.

    The manufacturer advises that the preparation may be taken during breastfeeding, however, as with all medicines, it should only be taken during breastfeeding when considered essential.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at

    Effects on Ability to Drive and Operate Machinery

    There are no known effects on the ability to drive or operate machinery.

    Side Effects

    Hypersensitivity reactions
    Muscular weakness
    Stomach discomfort


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Pharmacological Properties

    Shelf Life and Storage

    Do not store above 25 degrees C

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Summary of Product Characteristics: Rennie Fruit. Bayer plc. Revised October 2005

    Summary of Product Characteristics: Rennie Orange. Bayer plc. Revised April 2012

    Summary of Product Characteristics: Setlers Antacid tablets. Thornton & Ross Ltd. Revised June 2004

    Summary of Product Characteristics: TUMS Assorted Fruit Antacid Tablets. GlaxoSmithKline Consumer Healthcare. Revised April 2008

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Antacids, Oral Last revised: February 5, 2008
    Last accessed: May 17, 2012

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