Prevalence rates of thyroid in the US indicate that the condition needs to be treated to prevent complications. Roughly 20 million people in the US are afflicted with some form of thyroid disease. The alarming part of this statistic is that almost two-thirds of the individuals are unaware of the condition.  Consequently, the condition is left untreated and this leads to an entire range of consequences. Medications for treating thyroid include methimazole, among others for the treatment of hyperthyroidism. The following subsections explain all about this medication including the possible side effects of methimazole. This will help patients and caregivers identify the possible adverse outcomes and take necessary preventive or mitigative steps.

Overview of methimazole

The medication is also used prior to thyroid surgery or before radioactive iodine treatment in patients with an overactive thyroid. Available as a tablet, this is a prescription-only medication and is to be taken after proper diagnosis and only as per the recommendations of the specialist.

Belonging to the category of ethionamide antithyroid agent, the medication, as outlined above is used in the treatment of hyperthyroidism. It brings about a reduction in the thyroid hormone by preventing thyroid peroxidase from working.  In use for more than seventy years, it is typically recommended for patients who may not be suitable to undergo stronger treatment options like surgery/radioactive iodine therapy. The medication that inhibits the synthesis of thyroid hormones is ten times more potent than other medications when compared on a weight basis. The mechanism of action of the medication is inhibition of the synthesis of thyroid peroxidase, which is responsible for various conversion actions that result in the production of the hormones by the thyroid gland.

Precautions to be taken before using the medication

Medications come with the possibility of undesirable effects, and certain individuals may not be suitable to take certain types of medications. This could be due to existing conditions, or it could be the response of the body to the medication. It is, therefore, necessary for all patients to be aware of the possible outcomes and the suitability or unsuitability before taking the medication. A detailed discussion with the specialist regarding conditions will help determine suitability. Here is a look at some of the possible outcomes, including conditions that are safe with no effect on the patient. This is intended to allay fears or apprehensions about categories of individuals.

#1 Patients with a history of allergies – some precautions are required

Patients with a history of allergies to medications or substances need to take adequate precautions and speak to a specialist. This includes the need to learn all about possible allergic reactions and closely monitor, to identify any possible indications of allergies. This could include any history of allergies to food products, dyes or coloring agents, preservatives, and animal dander.

#2 Pediatric patients – safe with nil effects 

Parents of kids can do away with apprehensions of possible adverse outcomes as there have been no reports or documented effects of undesirable outcomes among pediatric patients on the medication.

#3 Geriatric patients – caution required due to lack of information about effects

There are certain conditions or categories of individuals who may require specific assessment about their suitability, due to a lack of adequate information about any possible unwanted effects. Geriatric patients belong to this category as to date enough studies have not been conducted.

#4 Breastfeeding women – precautions required due to unavailability of information

Breastfeeding women also belong to the above category of patients who need specific assessment. This is of extreme importance as it needs to be checked if the suckling infant will experience undesirable outcomes if the medication is passed through breast milk. In such instances, in the absence of suitable information, the most prudent option is to assess the importance of the medication and its outcomes – if it is extremely important or critical in nature, then the only option would be to continue the medication under close medical supervision with appropriate dosage.

Side effects of methimazoledrug interactions of the medication

All medications come with the possibility of drug interactions when taken along with other medications or substances. This includes prescription medications, OTC formulations, herbal remedies, supplements, and products that belong to the category of nutraceuticals. Most individuals often assume that medications will not react with supplements or herbal concoctions. However, this is wrong, as there is a possibility of a conflict in the mechanism of action or the properties of the two substances. This could result in one of three possibilities – one, an increase in the expected outcomes of either of the substances. Two, a decrease in the expected outcomes of either of the substance, and three, stronger side effects of either or both the medications.

Unlike side effects of medications that may be experienced differently by different users, drug interactions may be experienced in a relatively similar manner by patients. In instances, when the interactions are too strong, the specialist may recommend that intake of one of the two medications or substances be temporarily stopped. In certain instances, both the medications may be equally important and it may not be possible to halt either, and in such cases, the dosage may be altered or the intake schedule may be staggered to prevent interaction. Some of the medications that may interact with methimazole include bupropion, tegafur, acenocoumarol, phenindione, and warfarin. This is not a complete list and patients are to inform the doctor of all medications and substances in use.

Outcomes in patients with existing medical conditions

Patients with certain existing medical conditions are to take adequate precautions to prevent any undesirable outcomes. For instance, patients with low blood cell count or low red blood cells, or bone marrow issues are to intimate the doctor about the condition. Similarly, patients with low white blood cells or low platelets in the blood may also experience an aggravation of the condition when on the medication.

The possibility of patients experiencing stronger side effects from the medication exists in the following conditions. Patients with breathing issues, kidney conditions, liver disease, and lung disease may be exposed to the risk of stronger undesirable outcomes.

The right way to take the medication

It is necessary for patients to follow the intake instructions, to avoid undesirable effects. This includes the need to stay away from tobacco products, alcohol, or any other intoxicating substance, as there is a risk of unwanted effects. It is also necessary to take the tablet with food or without food as per the specific instructions of the doctor. Dosage and intake schedule are to be followed diligently, as the medication is known to work best when the required levels of the antithyroid agent are present in the blood. This makes it necessary to ensure that the schedule is maintained properly. Adult patients with hyperthyroidism are recommended anywhere between 15 to 60 mg daily, which is to be divided into three doses a day, with a follow-up maintenance dose that could be between 5 to 15 mg daily. The dosage for children is determined as per the body weight of the patient – and could be around 0.4 mg daily for every kilogram of body weight. This is to be divided into three doses daily, with a daily maintenance dose calculated as 0.2 mg for every kg of body weight.

In the event of patients missing out on doses, it is necessary to follow certain instructions. For instance, if the missed dose has been noticed a short time after the scheduled time, the patient may take the dose. However, if the missed dose has been noticed when it is close to the next dose, it is to be skipped. The doses are ideally recommended to be taken with a gap of eight hours between doses, and therefore it is important to ensure that patients do not end up taking double doses to make up for the missed doses. The best option in such instances is to skip the doses completely.

Routine monitoring or tests

Patients, especially children on the medication need to be monitored periodically and routinely to assess the effects of the medication. This will help learn more about the progress and will also help to prevent or mitigate any possible undesirable effects. This may include necessary blood and urine tests periodically, as recommended by the specialist. Women on the medication are ideally recommended to be on birth control medications to prevent pregnancies and avoid any unknown side effects on the fetus.

Commonly reported side effects of methimazole

Some of the commonly reported undesirable effects of the medication include hypothyroidism. Symptoms that are indicative of this condition include constipation, unusual depression, drying skin, hair that has lost its texture and vibrancy, hoarse voice, and possible muscle cramps. Other symptoms include a reduction in heartbeat rate, possible weight gain, and abnormal tiredness/fatigue.

Patients are look-out for certain tell-tale symptoms of undesirable effects such as discoloration of stools; where the stools appear dark in color. There is also the possibility of bleeding in the gums, and discoloration of urine; where the urine appears cloudy and dark. The patient may also experience a possible distinct burning sensation, apart from the pain in the chest that is not attributed to any other condition. Any difficulty in breathing is to be treated at the earliest to prevent the condition from deteriorating. There is also the possibility of low-grade fever in individuals on the medication. Other conditions include the outbreak of rashes on the skin, sudden loss of appetite, and pain in the lower back.

This is not a complete or exhaustive list of possible effects and is only intended to be a broad reference of the possible types of side effects. Patients are to identify and constantly be on the lookout for any new, unusual, or abnormal experience or condition when on the medication.

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