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Home > Drug Category > Thyroid Disorders > Propylthiouracil and Equivalent

Propylthiouracil Information

Propylthiouracil (Propylthiouracil) is primarily used to treat hyperthyroidism, a condition in which there is a high level of thyroid hormones in the blood, causing a myriad of symptoms such as rapid heartbeat, weight loss, heat intolerance, tremor, anxiety, etc. It is mainly used as one of the second-line treatments of common causes of hyperthyroidism, such as Graves' disease and toxic multinodular goitre. It is a thioamide (antithyroid agent) typically prescribed in specific scenarios where the preferred drug, methimazole, or radioactive iodine therapy is not suitable.

Hyperthyroidism can lead to serious complications, some of which can be life-threatening. One of the life-threatening complications includes thyroid storm, a medical emergency that causes extreme overactivity of the body’s metabolism. Propylthiouracil is typically used as one of the initial drugs of choice for the treatment of thyroid storm due to its added peripheral blocking effect.

Some thyroid conditions may require surgical removal of the thyroid gland or radioiodine therapy as definitive treatment. Propylthiouracil can be used to stabilize a patient's thyroid function before this surgery or radioactive iodine therapy. It is usually prescribed to prevent complications such as thyroid storm after these procedures.

Propylthiouracil blocks thyroid peroxidase, an enzyme needed for the production of thyroid hormones (T3 and T4) from iodine and tyrosine. Not only does it block thyroid hormone production, but it also prevents the conversion of thyroxine (T4) to the more active triiodothyronine (T3) in the body’s tissues, reducing the effects of excess thyroid hormones, an effect that makes it one of the desired medications in thyrotoxic crisis and thyroid storm.

Unlike first-line medications used in hyperthyroidism, such as methimazole, Propylthiouracil has a lower risk of causing congenital disabilities. This is why it is also the preferred medication in treating hyperthyroidism in pregnancy, especially in the first trimester of pregnancy. However, it is typically not used for long periods due to its potential adverse effects on the liver.

Propylthiouracil Side Effects

Some mild side effects of this medication include drowsiness, rash, itching, hair loss, changes in skin color, feeling sick, stomach upset, loss of taste, muscle or joint pain, pins-and-needles sensations, and headache. Contact your doctor if these side effects worsen or persist.

Propylthiouracil can cause serious adverse effects, most notably liver injury, including liver failure, which limits its long-term use. Therefore, stop taking this medicine and contact your doctor immediately if you experience any serious side effects, including the following:
• Allergic reactions such as breathing difficulties, body itching, body rash, skin blistering, swelling of the face, mouth, tongue, lips, or throat;
• Anemia (low red blood cells) with symptoms like dizziness, pale skin, unusual tiredness;
• Clotting problems with symptoms like unusual nosebleeds, bruising, and blood in urine;
• Encephalopathy (disease affecting the function or structure of the brain) with symptoms such as memory loss, personality changes, inability to concentrate, muscle twitches;
• Fever, sore throat, joint swelling and pain, muscle aches, blood in urine, shortness of breath, rash or other symptoms of infection or immune hyperactivity;
• Hypothyroidism with symptoms like dry skin, constipation, weight gain, fatigue;
• Kidney problems with symptoms like increased urination at night, decreased urine production;
• Liver problems with symptoms such as yellow eyes or skin, abdominal pain, pale stools, dark urine, and itching

Inform your doctor about any other side effects you notice that are not listed here.

Propylthiouracil Precautions

Do not use this medication if you are allergic to Propylthiouracil, other ingredients in this medication, or any other medicines. Before you start taking Propylthiouracil, ensure that you inform your doctor about any prior or current medical conditions, including the following:
• Blood cell count disorders, such as anemia or low white blood cells;
• Hypothyroidism (low thyroid hormones);
• Inflamed blood vessels (vasculitis);
• Kidney disease;
• Liver disease

Before starting this medication, your doctor may request baseline blood tests such as complete blood count and liver function tests. Routine monitoring continues throughout therapy. It is to ensure this medication is suitable for you and to monitor for any adverse effects. If you have planned surgery, you should inform your medical team about Propylthiouracil, as the dosage or management may need adjustment.

Propylthiouracil is generally preferred during the first trimester of pregnancy because methimazole has been associated with a greater risk of specific congenital anomalies if used during this critical period of organ development. However, after the first trimester, many guidelines suggest switching to methimazole, if possible, as the risk of liver toxicity with Propylthiouracil may outweigh the fetal risks of methimazole later in the pregnancy. Consult your doctor before using this medication while breastfeeding, as Propylthiouracil is usually excreted into breast milk in only small amounts.

Propylthiouracil can enhance the effect of oral blood thinners, thereby causing adverse anticoagulation and possible bleeding disorders. Therefore, before using this medication, inform your doctor about any other medications you are currently taking, including herbal medicines and supplements, to determine if it is safe to use along with Propylthiouracil.

Take Propylthiouracil tablets by mouth, usually two or three times daily, as directed by your doctor. Swallow the tablet with water, preferably at the exact times each day to maintain steady hormone control. Please, do not stop taking it suddenly without consulting your doctor first, as doing so can lead to a dangerous relapse of hyperthyroidism. Take it consistently, even if symptoms improve, until your doctor advises otherwise. Check out the leaflets in the medication pack for more usage instructions. Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do I need a prescription to order Propylthiouracil?

Yes, a prescription is required from your physician to order Propylthiouracil.