WP

What it is

WP CARBIMAZOLE 5 is a tablet containing 5 mg of carbimazole as the active ingredient. The tablets are white, round, uncoated tablets, debossed "5" on one side and break line on other side. Carbimazole is an anti-thyroid agent. Carbimazole is believed to exert its antithyroid effect by blocking the organic binding of iodine through inhibition of the iodination of tyrosine, and is also thought to have some action on peroxidase which is required as a catalyst in the synthesis of thyroxine by the thyroid gland.

Approved indications

— Therapy of hyperthyroidism. — Definitive therapy: induction of a permanent remission, in either primary or secondary thyrotoxicosis. — Preparation for thyroidectomy. — Before and after radioactive iodine treatment.

Dosing overview

It is customary to begin therapy with a dosage that will fairly quickly control the thyrotoxicosis and render the patient euthyroid, and later to reduce this. Usual initial dosages for adults are: mild cases, 15 to 20 mg/day in divided doses; moderate cases, 30 mg/day in divided doses; severe cases, 40 to 45 mg (up to 60 mg)/day in divided doses and should be titrated against thyroid function until the patient is euthyroid in order to reduce the risk of over-treatment and resultant hypothyroidism. When symptoms are controlled the dosage should be reduced to a maintenance level, which will usually be between 10 and 15 mg daily. Once a remission has been secured, maintenance dosage should be continued for at least 12 months, and up to 2 years of treatment may be required.

Key safety warnings

Fatal cases of agranulocytosis with carbimazole have been reported and early treatment of agranulocytosis is essential, so it is important that patients should always be warned about the onset of sore throats, bruising or bleeding, mouth ulcers, fever, malaise or other symptoms which might suggest bone marrow depression and should be instructed to stop the medicine and to seek medical advice immediately. Rare cases of pancytopaenia/aplastic anaemia, and very rare cases of haemolytic anaemia and thrombocytopaenia have been reported. There have been post-marketing reports of acute pancreatitis in patients receiving carbimazole or its active metabolite thiamazole, and in case of acute pancreatitis, carbimazole should be discontinued immediately. Cases of vasculitis resulting in severe complications have been reported in patients receiving carbimazole and methimazole therapy, including leukocytoclastic cutaneous vasculitis, acute kidney injury and glomerulonephritis, alveolar/pulmonary haemorrhage, CNS vasculitis, and neuropathy. Care should be taken to observe the contraindications and warnings as it has been reported that the risk of a fatal outcome to neutrophil dyscrasia may be greater in the elderly (aged 65 or over).

Contraindications

Carbimazole is contraindicated in patients with a previous history of adverse reactions to carbimazole or to any of the excipients in the composition. Retrosternal goitre. Serious pre-existing haematological conditions. Severe hepatic insufficiency. Patients with a history of acute pancreatitis after administration of carbimazole or its active metabolite thiamazole.

Regulatory history

WP CARBIMAZOLE 5 was first listed on the ARTG on 26 November 2021 under ARTG 349095.