9.2.2 Thyroid Drugs
Thyroid Drugs
From Pharmacology for Nurses- Ch 27
Learning Objectives
By the end of this section, you should be able to:
- 27.2.1 Identify the characteristics of thyroid and antithyroid drugs used to treat thyroid disorders.
- 27.2.2 Explain the indications, actions, adverse reactions, contraindications, and interactions of thyroid and antithyroid drugs used to treat thyroid disorders.
- 27.2.3 Describe nursing implications of thyroid and antithyroid drugs used to treat thyroid disorders.
- 27.2.4 Explain the client education related to thyroid and antithyroid drugs used to treat thyroid disorders.
Thyroid Drugs
Thyroid drugs are used when the thyroid is functioning incorrectly and there is a need to replace the thyroid hormone so that the body can maintain its expected function. Thyroid drugs can be synthetic thyroid hormones or animal-based thyroid hormones. These drugs act by replacing the body’s natural thyroid hormone when the levels are low or absent within the body.
Levothyroxine Sodium
Levothyroxine sodium is a synthetic thyroid hormone that is identical to T4 produced in the body. The gastrointestinal tract absorbs 40%–80% of this synthetic hormone. The drug is greater than 99% protein bound and easily distributed. It is primarily eliminated by the kidneys, with approximately 20% of T4 being excreted in the stool (Eghtedari & Correa, 2022). It comes in tablet and injectable forms and is used to treat hypothyroidism and pituitary TSH suppression. Levothyroxine is contraindicated in clients with uncorrected adrenal insufficiency: because of the role of adrenal glands in regulating stress response and cortisol production, levothyroxine’s ability to increase metabolic demands and stress may overwhelm the impaired adrenal glands, causing an adrenal crisis. Stabilization of adrenal function is crucial before starting levothyroxine treatment to prevent an adrenal crisis.
Levothyroxine sodium has a narrow therapeutic index; careful dose titration is necessary to avoid overtreatment or undertreatment. Clients should take this drug in the morning at least 30 minutes before consuming food or fluid containing caffeine such as coffee, tea, or soda. Food and caffeinated drinks can both interfere with the absorption of levothyroxine sodium.
Liothyronine Sodium
Liothyronine sodium is a synthetic thyroid hormone mimicking T3. This hormone replacement is commonly used to treat hypothyroidism and myxedema coma. Liothyronine can be taken orally, comes in an intravenous form, and is easily absorbed and readily distributed in the body. As with levothyroxine, liothyronine is contraindicated in clients with uncorrected adrenal insufficiency. As stated above, the adrenal glands control the stress response and cortisol levels within the body. When they are impaired, they are unable to handle the increase in metabolic rate caused by the administration of liothyronine, leading to an adrenal crisis. Adverse effects of liothyronine include anxiety, blurred vision, chest discomfort, decreased bone mineral density, and decreased urine output.
Safety Alert
Similarly Named Drugs
Do not confuse levothyroxine sodium with liothyronine sodium. Although these drugs are in the same drug class, they require different dosing and lab monitoring.
Desiccated Thyroid Extract
Desiccated thyroid extract is a thyroid hormone developed from pig glands that is often used as an over-the-counter remedy for thyroid hormone replacement. Desiccated thyroid extract has not been approved by the Food and Drug Administration (FDA) due to a complex manufacturing process leading to issues with safety, effectiveness, and quality, with inconsistent or inaccurate dosage. Table 27.2 lists common thyroid drugs and typical routes and dosing for adult clients.
| Drug | Routes and Dosage Ranges |
|---|---|
| Levothyroxine sodium (Synthroid, Levoxyl) | Individualized dosing due to a narrow therapeutic index. Standard dosing starts at 1.6 mcg/kg/day orally; increase by 12.5–25 mcg orally every 4–6 weeks if needed. Serum T4 levels should be used to monitor therapeutic dosing range of drug. Must be titrated based on the individual’s need and to avoid the consequences of overtreatment or undertreatment. |
| Liothyronine sodium (Cytomel, Triostat) |
25 mcg orally once daily; increase by 25 mcg orally daily every 1–2 weeks if needed. Maintenance dose: 25–75 mcg once daily. Serum T3 levels should be used to monitor therapeutic dosing range of drug. |
Adverse Effects and Contraindications
Common adverse effects among the thyroid drug classification include cardiac effects—such as tachycardia, palpitations, and arrhythmias—weight loss, nervousness and irritability, heat intolerance, diarrhea, abdominal cramping, headaches, and sleep disturbances.
Contraindications for thyroid drug classification include hypersensitivity to the drug or any of its components as well as any recent myocardial infarction because thyroid drugs can increase heart rate and heart contractility. Untreated adrenal insufficiency is a contraindication because impaired adrenal glands cannot handle the increased metabolic rate cause by thyroid drugs, as is hyperthyroidism since the drugs would increase thyroid hormone levels that are already elevated.
Table 27.3 is a drug prototype table for thyroid drugs featuring levothyroxine sodium. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.
| Drug Class Thyroid hormone
Mechanism of Action store thyroid hormone homeostasis within the body |
Drug Dosage Individualized dosing due to a narrow therapeutic index. Standard dosing starts at 1.6 mcg/kg/day orally; increase by 12.5–25 mcg orally every 4–6 weeks if needed. Serum T4 levels should be used to monitor therapeutic dosing range of drug. Must be titrated based on the individual’s need and to avoid the consequences of overtreatment or undertreatment. |
| Indications Hypothyroidism Pituitary TSH suppression
Therapeutic Effects |
Drug Interactions Dopamine Glucocorticoids Octreotide Amiodarone Digitalis Iodine Lithium Calcium Iron Warfarin
Food Interactions |
| Adverse Effects Irregular heartbeat Heat intolerance Irregular breathing Irritability Nausea Tremors Decreased urine output |
Contraindications Adrenal insufficiency Nontoxic goiter or nodular thyroid disease
Caution: |
27.3 Drug Prototype Table: Levothyroxine Sodium (source: https://dailymed.nlm.nih.gov/dailymed/)
Nursing Implications
The nurse should do the following for clients who are taking thyroid drugs:
- Educate the client that thyroid replacement hormone is a lifelong therapy.
- Assess the client’s knowledge about signs and symptoms of over- and undertreatment, adverse reactions, and contraindications and clarify any gaps in knowledge.
- Monitor thyroid functioning of the client and report any abnormalities or symptoms of thyroid storm, such as tachycardia, cardiac dysrhythmias, fever, heart failure, flushed skin, confusion, behavioral changes, and hypotension, to the health care provider.
- Provide client teaching regarding the drug and when to call the health care provider. See below for client teaching guidelines.
Client Teaching Guidelines
The client taking a thyroid drug should:
- Take on an empty stomach 1/2–1 hour before breakfast for better absorption.
- Keep a journal of their symptoms. It may take several weeks for them to notice improved symptoms.
- Report symptoms of irregular heartbeat, chest pain, shortness of breath, leg cramps, headache, nervousness, irritability, sleeplessness, and heat intolerance to their health care provider because these may represent an adverse reaction or toxicity to the drug.
- Notify the health care provider if they are pregnant or become pregnant because the dose of the drug may need to be increased during pregnancy.
- Store out of reach of children and away from heat, moisture, and light.
The client taking a thyroid drug should not:
- Stop taking unless directed by their health care provider because this drug class replaces their body’s missing thyroid hormone.
- Take with food because it will decrease the drug’s absorption.
- Take within 4 hours of taking calcium and/or iron supplements, including calcium antacids, because they may impact the drug’s absorption.
FDA Black Box Warning
Thyroid Hormones
Thyroid hormones, including levothyroxine sodium, either alone or with other therapeutic agents, should not be used for treatment of obesity or weight loss due to producing serious toxicity or life-threatening manifestations.
Next- 9.3 Glossary
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