Two medicines, side by side
Levothyroxine vs methimazole
Levothyroxine is labeled for hypothyroidism; methimazole has no indication this site maps. Their labels share no use, so they are not alternatives to each other. Drugs@FDA records approvals of levothyroxine since 2000 and of methimazole since 1950. Pharmacies paid $0.0588 per levothyroxine 112 mcg tablet and $0.0702 per methimazole 5 mg tablet (NADAC, October 7, 2026); the strengths differ, so the two prices are not like for like. In FDA's classes, levothyroxine is a l-thyroxine and methimazole a thyroid hormone synthesis inhibitor.
Check it at the source: the levothyroxine FDA label on DailyMed (effective February 20, 2024); the methimazole FDA label on DailyMed (effective August 20, 2026).
Highlights of the levothyroxine record
Levothyroxine (Synthroid) · label of February 20, 2024
NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including SYNTHROID, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction.
Used for
From the label: indicationsHypothyroidism SYNTHROID is indicated in adult and pediatric patients, including neonates, as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. […]
On the market
- Earliest approval on file
- August 21, 2000
- Generic labelers
- 36 labelers
- Pharmacy cost
- $0.0588 per tablet
Supply and safety
- Shortage
- No current entry
- Recalls
- 128
Highlights of the methimazole record
Methimazole (Tapazole) · label of August 20, 2026
Used for
From the label: indicationsMethimazole tablets are indicated: In patients with Graves’ disease with hyperthyroidism or toxic multinodular goiter for whom surgery or radioactive iodine therapy is not an appropriate treatment option. To ameliorate symptoms of hyperthyroidism in preparation for thyroidectomy or radioactive iodine therapy.
On the market
- Earliest approval on file
- June 21, 1950
- Generic labelers
- 21 labelers
- Pharmacy cost
- $0.0702 per tablet
Supply and safety
- Shortage
- No current entry
- Recalls
- 0
Source: FDA drug labels via openFDA (Levothyroxine label of February 20, 2024, Methimazole label of August 20, 2026); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do levothyroxine and methimazole differ on the record?
In FDA's classes, levothyroxine is a l-thyroxine and methimazole a thyroid hormone synthesis inhibitor.
Only the levothyroxine label carries a boxed warning.
Generics: levothyroxine since 2002; methimazole since 2000 (Drugs@FDA).
| Levothyroxine | Methimazole | |
|---|---|---|
| Labeled for | Hypothyroidism | n/a |
| Pharmacologic class | l-Thyroxine | Thyroid Hormone Synthesis Inhibitor |
| How it works (label) | Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Triiodothyronine (T3) and L-thyroxine (T4) diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. | n/a |
| Half-life (label) | n/a | n/a |
| Earliest approval on file (Drugs@FDA) | August 21, 2000 | June 21, 1950 |
| First generic approved | June 5, 2002 | March 29, 2000 |
| Generic labelers (NDC) | 36 labelers | 21 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.0588 per tablet (Levothyroxine 112 mcg tablet) | $0.0702 per tablet (Methimazole 5 mg tablet) |
| 12-month price change | -12% | -18% |
| Boxed warning | Yes | No |
| Shortage now | No current entry | No current entry |
| Recalls recorded | 128 | 0 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 300,456 | 7,805 |
| DEA schedule | none | none |
Source: Drugs@FDA, FDA NDC Directory, CMS NADAC of October 7, 2026, FDA shortages and recalls, FAERS via openFDA (FDA files October 8, 2026)
Do their labels mention each other?
Levothyroxine label, drug interactionsDrug or Drug Class: Aminoglutethimide Amiodarone Iodide (including iodine-containing Radiographic contrast agents) Lithium Methimazole Propylthioracil (PTU) Sulfonamides Tolbutamide; Effect: Long-term lithium therapy can result in goiter in up to 50% of patients, and either subclinical or overt hypothyroidism, each in up to 20% of patients. …
Source: FDA drug labels via openFDA
What next?
- Alternatives to levothyroxine
- every medicine labeled for the same conditions