Thyzac 5

Indications

• Hyperthyroidism
• Graves' disease
• Thyrotoxicosis

Dosage

Children: For children, carbimazole is used to control hyperthyroidism, generally for 8 to 12 weeks. The specific dose should be determined by a

Adults: 15–40 mg daily, continued until the patient becomes euthyroid, usually after 4 to 8 weeks. Higher doses should be prescribed under specialist supervision only, then reduced to 5–15 mg daily. For blocking-replacement regimen, 40–60 mg daily in combination with levothyroxine is advised, typically for 18 months.

Mechanism of action

Carbimazole decreases the uptake and concentration of inorganic iodine by the thyroid gland. Once metabolized to its active form, methimazole, it inhibits the thyroid peroxidase enzyme, which is crucial for the coupling and iodination of tyrosine residues on thyroglobulin. This inhibition ultimately reduces the synthesis of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine).

Pharmacodynamics

Carbimazole exhibits its antithyroid effects through its conversion to methimazole in the body. This conversion is pivotal in reducing the production of thyroid hormones, thereby managing hyperthyroid states. The drug is effective in controlling symptoms associated with excessive thyroid hormone levels and is often used as a preoperative treatment for patients undergoing thyroidectomy.

Pharmacokinetics

Carbimazole is absorbed orally and is metabolized in the liver to methimazole, which is the active form responsible for its therapeutic effects. The half-life of carbimazole can be prolonged in patients with hepatic impairment. The drug is present in breast milk, but this generally does not contraindicate breastfeeding, provided that neonatal development is monitored closely.

Contra-indications

• Severe blood disorders
• Bone marrow disorders
• A history of acute pancreatitis associated with previous treatment

Adverse effects

• Neutropenia
• Agranulocytosis
• Severe cutaneous adverse reactions (SCARs)
• Haemolytic anaemia
• Alopecia
• Nausea
• Headache
• Skin reactions
• Salivary gland enlargement
• Taste loss
• Malaise
• Myopathy
• Hepatic disorders
• Pancreatitis

Interactions

• Metyrapone (severe interaction - decreases effects)
• Digoxin (moderate interaction - affects concentration)

Precautions

• Use with caution in hepatic impairment
• Monitor white blood cell count regularly
• Consider benefit-risk assessment for use in pregnancy
• Breastfeeding should only continue if neonatal development is monitored

Pregnancy

Consider use only after a thorough benefit-risk assessment. Carbimazole is associated with an increased risk of congenital malformations.

Breast-feeding

Present in breast milk but does not preclude breastfeeding as long as neonatal development is closely monitored and the lowest effective dose is used.

Storage

Store in a cool, dry place, away from direct sunlight.

Formulations

• Carbimazole 5 mg tablets
• Carbimazole 10 mg tablets
• Carbimazole 15 mg tablets
• Carbimazole 20 mg tablets
• Carbimazole oral suspension

Indications

• Used as a disintegrant in tablet formulations
• Enhances the bioavailability of active pharmaceutical ingredients

Dosage

Children: Refer to the specific formulation guidelines, as dosage will vary based on the active ingredient and formulation type.

Adults: Refer to the specific formulation guidelines, as dosage will vary based on the active ingredient and formulation type.

Mechanism of action

Croscarmellose sodium works by swelling and absorbing water when it comes into contact with gastrointestinal fluids. This swelling leads to the rapid disintegration of the tablet or capsule matrix, facilitating the release and absorption of the active pharmaceutical ingredients.

Pharmacodynamics

Croscarmellose sodium is classified as a superdisintegrant. Its ability to rapidly disintegrate solid dosage forms can significantly enhance the dissolution rate of the active ingredient, which is crucial for achieving therapeutic effects in a timely manner.

Pharmacokinetics

Croscarmellose sodium is not absorbed in the gastrointestinal tract and does not exert pharmacological effects in the body. It is considered non-toxic and is excreted unchanged. Its main role is as an excipient, influencing the formulation's characteristics rather than the pharmacokinetics of the active ingredients.

Precautions

• Use with caution in patients with known hypersensitivity to croscarmellose or its components.

Pregnancy

Safety in pregnancy has not been established. Use only if clearly needed.

Breast-feeding

Caution is advised when using during breastfeeding, as safety has not been established.

Storage

Store in a cool, dry place, away from moisture and heat.

Formulations

• Powder
• Granules

Indications

• Lactose intolerance
• As a filler or excipient in pharmaceutical formulations

Dosage

Children: Refer to the BNF for Children for specific dosing information based on age and clinical context.

Adults: Refer to the BNF for specific dosing information based on clinical context.

Mechanism of action

Lactose is metabolized in the intestine by the enzyme lactase into its constituent monosaccharides, glucose and galactose. In individuals with lactase deficiency, unabsorbed lactose passes into the colon, where it is fermented by bacteria, leading to gas production and osmotic effects that contribute to diarrhea.

Pharmacodynamics

The pharmacodynamics of lactose are primarily related to its effects on gastrointestinal function. In healthy individuals, lactose is effectively broken down into glucose and galactose, which are absorbed and utilized for energy. In individuals with lactose intolerance, the unabsorbed lactose can cause osmotic diarrhea and colonic fermentation, leading to discomfort and symptoms associated with lactose intolerance.

Pharmacokinetics

Lactose is not absorbed in the gastrointestinal tract until it is hydrolyzed into glucose and galactose by lactase. The absorption of glucose and galactose occurs in the small intestine. The half-life is not applicable as lactose is not typically administered as a medication but is rather ingested as a natural component of food. Its metabolism primarily occurs in the intestine.

Adverse effects

• Bloating
• Diarrhea
• Abdominal pain
• Flatulence

Precautions

• Use with caution in patients with lactose intolerance.
• Consider potential for gastrointestinal upset in sensitive individuals.

Pregnancy

Lactose is generally considered safe for use during pregnancy. However, consult a healthcare professional for individual advice.

Breast-feeding

Lactose is safe to use while breastfeeding, as it is a natural sugar present in breast milk.

Storage

Store in a cool, dry place, away from direct sunlight.

Formulations

• Powder
• Granules
• Tablets
• Syrup

Mechanism of action

Carbimazole is an aitithyroid agent that decreases the uptake and concentration of inorganic iodine by thyroid, it also reduces the formation of di-iodotyrosine and thyroxine. Once converted to its active form of methimazole, it prevents the thyroid peroxidase enzyme from coupling and iodinating the tyrosine residues on thyroglobulin, hence reducing the production of the thyroid hormones T3 and T4.

Pharmacodynamics

Carbimazole is a carbethoxy derivative of methimazole. Its antithyroid action is due to its conversion to methimazole after absorption. It is used to treat hyperthyroidism and thyrotoxicosis.