Thyroid Med Hypo PDF

**Prototype: methimazole (Tapazole)** **Methimazole is a first-line drug for treating hyperthyroidism and works by inhibiting thyroid hormone synthesis.** ** ** - **Category**: Thionamide (Antithyroid Drug)  - **Primary Function**: Methimazole is specifically designed to treat hyperthyro...

**Prototype: methimazole (Tapazole)** **Methimazole is a first-line drug for treating hyperthyroidism and works by inhibiting thyroid hormone synthesis.** ** ** - **Category**: Thionamide (Antithyroid Drug)  - **Primary Function**: Methimazole is specifically designed to treat hyperthyroidism by inhibiting thyroid hormone synthesis. It is a first-line drug for treating hyperthyroidism.  - **Unique Features**: Methimazole is safer and more convenient than PTU and is preferred by most people, except clients who are pregnant (first trimester) or breastfeeding or those in thyroid storm. Methimazole is preferred in the second and third trimesters of pregnancy.  Mechanism of Action - Methimazole blocks the enzyme thyroid peroxidase, which is involved in the synthesis of thyroid hormones T3 and T4, effectively reducing their levels in the body. It does not impact existing thyroid hormone stores, meaning it takes 3 to 12 weeks to have a meaningful effect on thyroid hormone levels. As these thyroid hormone levels (T3 and T4) drop, the negative feedback mechanism to the pituitary gland is altered, leading to an increase in the secretion of thyroid-stimulating hormone (TSH), which is then monitored to determine whether the client has achieved a euthyroid state.  Indications and Therapeutic Uses - **Hyperthyroidism**: Methimazole is primarily used for the management of hyperthyroidism by reducing the excessive production of thyroid hormones. This includes hyperthyroidism from Graves disease or those in thyroid storm, although PTU is preferred for thyroid storm.  - **Thyroid Hormone Regulation**: Methimazole can also be used to regulate and suppress thyroid hormone synthesis in clients preparing for thyroid surgery or as an adjunct to radiation therapy. Side Effects and Adverse Reactions **Side Effect** **Description** ----------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Agranulocytosis Methimazole can cause this condition where white blood cell counts decrease, leading to an increased risk of infection. This usually develops in the first two months of therapy, and clients may first experience sore throat and fever. This necessitates the discontinuation of methimazole. Hypothyroidism Supratherapeutic doses can cause a transition from hyperthyroidism to this state. Reducing the dose can fix this, or thyroid hormone replacement may be required temporarily. Precautions and Contraindications **Precautions** - Use with caution in clients with liver dysfunction.  - Use with caution in clients with immunosuppression due to increased infection risk.  **Contraindications** - Contraindicated in the first trimester of pregnancy due to the risk of fetal harm. Use in the second and third trimesters is safe.  Drug Interactions - Methimazole can interact with anticoagulants like** \[warfarin\]**, enhancing their effect.  - Methimazole requires careful monitoring when administered with drugs that impact **\[white blood cell counts\]** due to the risk of agranulocytosis.  Dosing, Administration, & Client Teaching **Dosing** - Dosing varies based on the condition, severity, and client response.  - Check drug dosing guidelines for individualized dosing.  - PO dosing, once per day.  - For clients with severe disease, dosing begins high and decreases to a maintenance dose based on TSH.  - Treatment usually lasts 1-2 years.  - Once discontinued, if hyperthyroidism recurs, another round of methimazole, radiation therapy, or surgery (thyroidectomy) can be tried.  **Administration** - PO administration.  **Client Teaching** - Advise clients to immediately report any signs of infection or adverse effects to their healthcare provider.  - Advise clients who are pregnant or attempting to become pregnant to discuss with their provider, as methimazole is not safe in the first trimester.  - Advise clients to monitor for signs of hyper and hypothyroidism and report to their provider.  Labs to Monitor **Thyroid Function Labs ** - Monitor TSH levels 3-12 weeks after starting treatment to determine if euthyroid state has been achieved with medication therapy (TSH should increase to normal levels with a goal range of 0.5-2 microunits/mL).   **Complete Blood Count (CBC) ** - Monitor CBC, as methimazole can cause agranulocytosis.  **Prototype: propylthiouracil (PTU) ** Although PTU works to reduce thyroid hormone synthesis (similar to methimazole), it is a second-line treatment for hyperthyroidism. - **Category**: Thionamide (Antithyroid Drug)  - **Primary Function**: PTU is used primarily to manage hyperthyroidism by reducing the synthesis of thyroid hormones. It is a second-line drug for hyperthyroidism, with notable exceptions.  - **Unique Features**: Since it is more toxic than methimazole, PTU is preferred for clients in the first trimester of pregnancy, clients in thyroid storm, or clients who are intolerant of methimazole.  Mechanism of Action - PTU inhibits the enzyme thyroid peroxidase, leading to a reduction in thyroid hormone synthesis. Additionally, it impedes the peripheral conversion of thyroxine T4 to T3, lowering thyroid hormone levels in the bloodstream. The peripheral action of PTU makes it preferable in thyroid storm. As these thyroid hormone levels (T3 and T4) drop, the negative feedback mechanism to the pituitary gland is altered, leading to an increase in the secretion of thyroid-stimulating hormone (TSH), which is then monitored to determine whether the client has achieved a euthyroid state.  Indications and Therapeutic Uses - **Hyperthyroidism**: PTU is primarily used for the management of hyperthyroidism by reducing the excessive production of thyroid hormones. PTU is preferred for clients in the first trimester of pregnancy, clients in thyroid storm, or clients who are intolerant of methimazole. Side Effects and Adverse Reactions **Liver Injury** **Although rare, PTU has caused this in previous clients, requiring transplants or causing death. It happens so rapidly that performing routine lab testing does not usually help.** ------------------ --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- **Side Effect** **Description** Liver Injury Although rare, PTU has caused this in previous clients, requiring transplants or causing death. It happens so rapidly that performing routine lab testing does not usually help. Agranulocytosis PTU can cause this condition where white blood cell counts decrease, leading to an increased risk of infection. This usually develops in the first two months of therapy, and clients may first experience sore throat and fever. This necessitates the discontinuation of PTU. Hypothyroidism Supratherapeutic doses can cause a transition from hyperthyroidism to this state. Reducing the dose can fix this, or thyroid hormone replacement may be required temporarily. Precautions and Contraindications **Precautions** - Use with caution in clients with immunosuppression due to increased infection risk. **Contraindications** - Contraindicated in the first trimester of pregnancy due to the risk of fetal harm. Use in the second and third trimesters is safe. - Contraindicated in clients with liver dysfunction. **Black Box Warning** - PTU can cause serious liver damage, requiring a transplant or potentially causing death. Drug Interactions - PTU may interact with other medications that also affect** \[liver\]** function. - PTU requires careful monitoring when administered with drugs that impact **\[white blood cell counts\]** due to the risk of agranulocytosis. Dosing, Administration, & Client Teaching **Dosing** - Dosing varies based on the condition, severity, and client response. - Check drug dosing guidelines for individualized dosing. - PO dosing multiple times per day due to short half-life. - Use PTU in the first trimester of pregnancy only (methimazole is indicated for the second and third trimesters). - Use PTU in thyroid storm. - For clients with severe disease, dosing begins high and decreases to a maintenance dose based on TSH. - Treatment usually lasts 1-2 years. **Administration** - PO administration. **Client Teaching** - Advise client to monitor for signs of liver toxicity and report them to their provider immediately. - Advise clients to immediately report any signs of infection or adverse effects to their healthcare provider. - Advise clients who are pregnant or attempting to become pregnant to discuss with their provider as PTU is not safe in the second or third trimester. - Advise clients to monitor for signs of hyper and hypothyroidism and report to their provider. Labs to Monitor **Thyroid Function Labs** - Monitor TSH levels to determine if euthyroid state has been achieved with medication therapy (TSH should increase to normal levels with a goal range of 0.5-2 microunits/mL). **Complete Blood Count (CBC)** - Monitor CBC, as methimazole can cause agranulocytosis. **Liver Function Tests (LFTs) ** - Liver function tests may be required in clients where liver toxicity is suspected.