4.1. Therapeutic indications

Addisonian pernicious anaemia. Prophylaxis and treatment of other macrocytic anaemias associated with vitamin B12 deficiency. Schilling test.

Not indicated for treatment of toxic amblyopias - use Neo-Cytamen.

4.2. Posology and method of administration

Route of administration: intramuscular.

Adults and Children

Addisonian pernicious anaemia and other macrocytic anaemias without neurological involvement:

Initially: 250 to 1000mcg intramuscularly on alternate days for one to two weeks, then 250mcg weekly until the blood count is normal.

Maintenance: 1000mcg monthly.

Addisonian pernicious anaemia and other macrocytic anaemias with neurological complications:

Initially: 1000mcg intramuscularly on alternate days as long as improvement is occurring.

Maintenance: 1000mcg monthly.

Prophylaxis of macrocytic anaemia associated with vitamin B12 deficiency resulting from gastrectomy, some malabsorption syndromes and strict vegetarianism:

250mcg - 1000mcg monthly.

Schilling Test:

An intramuscular injection of 1000mcg cyanocobalamin is an essential part of this test.

4.3. Contraindications

Hypersensitivity to cyanocobalamin or any other constituents

Cytomen should not be used for the treatment of megaloblastic anaemia of pregnancy unless vitamin B12 deficiency has been demonstrated.

Not indicated for treatment of toxic amblyopias - use Neo-Cytamen.

4.4. Special warnings and precautions for use

Precautions:

The dosage schemes given above are usually satisfactory, but regular examination of the blood is advisable. If megaloblastic anaemia fails to respond to Cytamen, folate metabolism should be investigated. Doses in excess of 10mcg daily may produce an incomplete haematological response in patients with folate deficiency. Indiscriminate administration may mask the true diagnosis. The haematological and neurological state should be monitored regularly to ensure adequacy of therapy. Cardiac arrhythmias secondary to hypokalaemia during initial therapy have been reported. Plasma potassium should therefore be monitored during this period. Platelet count should be monitored during the first weeks of use in megaloblastic anaemia due to the possible occurrence of reactive thrombocytosis.

This medicine contains less than 1mmol (23mg) sodium per dose, that is to say essentially 'sodium-free'.

4.5. Interaction with other medicinal products and other forms of interaction

Chloramphenicol-treated patients may respond poorly to Cytamen. Serum concentrations of cyanocobalamin may be lowered by oral contraceptives but this interaction is unlikely to have clinical significance.

Antimetabolites and most antibiotics invalidate vitamin B12 assays by microbiological techniques.

4.6. Pregnancy and lactation

Cytamen should not be used for the treatment of megaloblastic anaemia of pregnancy unless vitamin B12 deficiency has been demonstrated. Cytamen is secreted into breast milk but this is unlikely to harm the infant, and may be beneficial if the mother and infant are vitamin B12 deficient.

4.7. Effects on ability to drive and use machines

None.

4.8. Undesirable effects

Hypersensitivity reactions have been reported including skin reactions (e.g. rash, itching) and exceptionally anaphylaxis. Other symptoms reported include fever, chills, hot flushing, dizziness, malaise, nausea, acneiform and bullous eruptions, tremor and injection site reactions including injection site pain, injection site induration and injection site necrosis. Reactive thrombocytosis can occur during the first weeks of use in megaloblastic anaemia.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme Website www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.

4.9. Overdose

Treatment is unlikely to be needed in cases of overdosage.