CONTRAPAQUE 300

Indications

• Iodine deficiency
• Goiter
• Hypothyroidism
• Thyroiditis
• Fibrocystic breast disease

Dosage

Children: Refer to the BNF for Children for appropriate dosing guidelines based on age and weight.

Adults: Refer to the BNF for appropriate dosing guidelines based on condition and clinical judgment.

Mechanism of action

Molecular iodine inhibits the induction and promotion of carcinogenesis in mammary tissues and has shown beneficial effects in fibrocystic breast disease. It temporarily decreases thyroid hormone production through the acute Wolff-Chaikoff effect, followed by a return to normal hormone synthesis due to down regulation of the sodium-iodide symport. This mechanism can lead to a transient hypothyroid state in some individuals with underlying thyroid conditions.

Pharmacodynamics

Iodine is vital for the synthesis of thyroid hormones thyroxine (T4) and triiodothyronine (T3). It affects the metabolism of amine-derived hormones and plays a role in amino acid metabolism. The acute excess of iodide can lead to decreased circulating levels of T4 and T3 in susceptible individuals, while most people can escape this effect and maintain normal thyroid function.

Pharmacokinetics

Iodine is absorbed primarily in the gastrointestinal tract and is distributed throughout the body, particularly in the thyroid gland, where it is concentrated for hormone synthesis. The kidney plays a significant role in the excretion of excess iodine. The half-life of iodine in the body varies and can be influenced by dietary intake and underlying health conditions.

Adverse effects

• Hypothyroidism
• Hyperthyroidism
• Iodine allergy
• Gastrointestinal disturbances

Interactions

• Thyroid hormones
• Antithyroid drugs
• Lithium
• Diuretics

Precautions

• Use with caution in patients with thyroid dysfunction
• Monitor thyroid function periodically during treatment
• Pregnant or breastfeeding women should consult a healthcare provider before use

Pregnancy

Iodine is essential for fetal thyroid hormone synthesis, but excessive iodine intake should be avoided.

Breast-feeding

Iodine is excreted in breast milk; consult a healthcare provider regarding supplementation.

Storage

Store in a cool, dry place away from light.

Formulations

• Iodine solution
• Iodine tincture
• Potassium iodide tablets

Indications

• Myelography
• Arthrography
• Nephroangiography
• Arteriography
• Computed tomography (CT) scans with contrast

Dosage

Children: Refer to BNF for Children for specific dosing recommendations based on age, weight, and the type of procedure.

Adults: Refer to BNF for specific dosing guidelines based on the type of procedure and patient condition.

Mechanism of action

Organic iodine compounds block x-rays as they pass through the body, thereby allowing body structures containing iodine to be delineated in contrast to those structures that do not contain iodine. The degree of opacity produced by these compounds is directly proportional to the total amount of the iodinated contrast agent in the path of the x-rays. After intrathecal administration, diffusion of iohexol in the CSF allows visualization of the subarachnoid spaces of the head and spinal canal. After intravascular administration, iohexol makes opaque those vessels in its path of flow, allowing visualization of the internal structures until significant hemodilution occurs.

Pharmacodynamics

Iohexol is an effective non-ionic, water-soluble contrast agent used in various radiographic procedures such as myelography, arthrography, nephroangiography, and arteriography. Its low systemic toxicity is due to both low chemotoxicity and low osmolality, making it safer for patients compared to older contrast agents.

Pharmacokinetics

Iohexol is administered intravascularly or intrathecally, where it diffuses into the bloodstream or cerebrospinal fluid, respectively. It is excreted primarily through the kidneys; thus, renal function can affect its clearance. The half-life and distribution can vary based on the route of administration and the individual's physiological characteristics.

Contra-indications

• Known hypersensitivity to iohexol or any of its components
• Severe dehydration
• Severe renal impairment (eGFR <30 mL/min)

Adverse effects

• Nausea
• Vomiting
• Headache
• Dizziness
• Urticaria
• Anaphylactic reactions
• Renal impairment
• Extravasation

Interactions

• Other nephrotoxic agents may increase the risk of renal impairment when used with iohexol
• Metformin: there is a risk of lactic acidosis in patients with renal impairment after administration of iodinated contrast agents

Precautions

• Assess renal function prior to administration, especially in patients with pre-existing renal impairment
• Use caution in patients with a history of asthma or allergic reactions
• Ensure adequate hydration before and after the procedure to minimize the risk of nephrotoxicity
• Monitor for signs of anaphylaxis during and after administration

Pregnancy

Iohexol should only be used in pregnancy if the potential benefit justifies the potential risk to the fetus. It is classified as a Category B drug.

Breast-feeding

It is generally considered safe to use iohexol during breastfeeding, but it is advised to monitor the infant for any potential adverse effects.

Storage

Store at room temperature, between 15°C and 30°C. Protect from light. Do not freeze.

Formulations

• Iohexol injection (various concentrations available)

Mechanism of action

Molecular iodine is known to inhibit the induction and promotion of N-methyl-n-nitrosourea-induced mammary carcinogenesis, to regress 7,12-dimethylbenz(a)anthracene-induced breast tumors in rats.It has also been shown to have beneficial effects in fibrocystic human breast disease. An acute iodide excess (above the preexisting dietary intake) transiently decreases the production of thyroid hormones in the thyroid gland; this is referred to as the acute Wolff-Chaikoff effect. In normal people, this is followed by a return to normal levels of hormone synthesis, referred to as escape from the acute Wolff-Chaikoff effect, without a significant change in circulating hormone levels. Escape is thought to be the result of down regulation of the sodium-iodide symport (NIS), the iodide transporter in the thyroid gland, resulting in a decrease in the intrathyroidal iodine and the resumption of normal hormone synthesis. An acute or chronic excess of iodide can also decrease circulating T4 and T3 levels and induce a hypothyroid state in some people who have underlying thyroid disorders. These effects are the result of a failure to escape from the acute Wolff-Chaikoff effect. Most people who experience iodine-induced hypothyroidism recover when the excess iodine intake is discontinued.

Mechanism of action

Organic iodine compounds block x-rays as they pass through the body, thereby allowing body structures containing iodine to be delineated in contrast to those structures that do not contain iodine. The degree of opacity produced by these compounds is directly proportional to the total amount (concentration and volume) of the iodinated contrast agent in the path of the x-rays. After intrathecal administration into the subarachnoid space, diffusion of iohexol in the CSF allows the visualization of the subarachnoid spaces of the head and spinal canal. After intravascular administration, iohexol makes opaque those vessels in its path of flow, allowing visualization of the internal structures until significant hemodilution occurs.

Pharmacodynamics

Iohexol is an effective non-ionic, water-soluble contrast agent which is used in myelography, arthrography, nephroangiography, arteriography, and other radiographic procedures. Its low systemic toxicity is the combined result of low chemotoxicity and low osmolality.