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Calcium acetate and magnesium carbonate oral

Updated 2 Feb 2023 | Phosphate binders


Oral formulations containing calcium acetate 435 mg (equivalent to 110 mg calcium) and magnesium carbonate, heavy 235 mg (equivalent to 60 mg magnesium)

Drugs List

  • calcium acetate with magnesium carbonate 435mg+235mg film coated tablets
  • OSVAREN 435mg+235mg film coated tablets
  • Therapeutic Indications


    Hyperphosphataemia in chronic renal failure patients on haemodialysis
    Hyperphosphataemia in patients on continuous ambulatory peritoneal dialysis



    3 to 10 film-coated tablets per day, to a maximum dosage of 12 tablets each day, depending on the serum phosphate level.


    3 to 10 film-coated tablets per day, to a maximum dosage of 12 tablets each day, depending on the serum phosphate level.


    Children under 18 years
    Restricted sodium intake
    Hereditary fructose intolerance
    Myasthenia gravis
    Third degree atrioventricular block

    Precautions and Warnings

    Predisposition to hypercalcaemia
    Glucose-galactose malabsorption syndrome

    Sodium content of formulation may be significant
    Preparation contains sucrose
    Monitor ECG in patients on digoxin
    Monitor serum calcium levels
    Monitor serum calcium on prolonged use or with high doses of vitamin D
    Monitor serum magnesium levels periodically
    Monitor serum phosphate levels
    Advise patients to report signs of hypercalcaemia
    Consider dose reduction for subsequent doses if severe diarrhoea occurs
    Risk of vascular and soft tissue calcifications in long-term therapy
    Advise patients to avoid calcium containing antacids
    Advise patients to avoid magnesium containing antacids

    Continuous monitoring of serum phosphate, serum magnesium, serum calcium and the calcium-phosphate-product should be performed, even more so in case of simultaneous intake vitamin D preparations and thiazide diuretics.

    Monitor ECG and serum calcium in patients on digitalis glycosides.

    Treatment of severe hyperphosphatemia with a calcium-phosphate-product of more than 5.3 mmol squared /L squared should be undertaken only if the patient is refractory to therapy, refractory to hyperkalaemia, has clinically relevant bradycardia or second-degree AV-block with bradycardia. In such cases continuous monitoring of serum calcium, magnesium and phosphate should take place.

    High doses and long-term administration of this medicine may result in hypermagnesaemia, which is normally asymptomatic, but in some cases systemic effects may be seen.

    Patients with chronic renal insufficiency may develop hypercalcaemic episodes, especially in combination with the administration of metabolites of vitamin D.

    The risk of vascular and soft tissue calcifications decrease by lowering the calcium-phosphate-product to <4.5 mmol squared /L squared.

    Increased intake of calcium salts may result in the precipitation of fatty acids and bile acid as calcium soap, which may lead to constipation.

    If possible, any other medication should not be taken within the period 2 hours before and 3 hours after the administration of this medicine, because the rate and/or extent of absorption of it may vary when used concurrently with this medicine.

    Pregnancy and Lactation


    Calcium acetate and magnesium carbonate tablets should be used with caution in pregnancy.

    There are no animal and clinical data available. Calcium acetate and magnesium carbonate cross the placenta. It is not known whether this medicine can cause foetal defects when it is administered during pregnancy or whether it can affect fertility. Therefore, this medicine should be administered to pregnant women only if the potential benefits clearly outweigh the risks.

    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 to 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 ( ).


    Calcium acetate and magnesium carbonate tablets should not be used during breastfeeding.

    Calcium acetate and magnesium carbonate are distributed in breast milk. Therefore, breastfeeding is not recommended during treatment with this medicine.

    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


    Patient should be warned of the possible symptoms of hypercalcaemia and/or hypermagnesemia.

    Advise patients to seek medical advise prior to taking any vitamin D supplements or antacids containing calcium or magnesium salts.

    If the tablets are too large to be swallowed by the patient then they can be broken along the score line but must be swallowed immediately to avoid the development of taste of acetic acid.

    In case of a missed dose, advise the patient to take the next dose at the normal time, no attempt should be made to make up for the missed dose.

    Advise the patient not to take oral medicinal products within the period 2 hours before and 3 hours after the administration of this medicine, because the rate and/or extent of absorption of it may vary when used concurrently with this medicine.

    Side Effects

    Changes in bone mineralisation
    Gastric irritation
    Sensation of fullness
    Soft or liquid stools
    Soft tissue calcification
    Vascular calcification


    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 ( ).

    Further Information

    Last Full Review Date: September 2016

    Reference Sources

    Joint Formulary Committee. British National Formulary. 71st ed. London: BMJ Group and Pharmaceutical Press; 2016.

    Summary of Product Characteristics: Osvaren 435mg/ 235mg film-coated tablets. Vifor Fresenius Medical Care Renal Pharma UK Ltd. Dated January 2011.

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