Synthroid vs Symbicort: side-by-side comparison
Synthroid (Hormones and Birth Control) and Symbicort (Respiratory Medications) belong to different therapeutic classes and are rarely interchangeable. This page compares the medications' purposes, mechanisms and the situations where each is used.
| Property | Synthroid | Symbicort |
|---|---|---|
| Active ingredient | Levothyroxine | Budesonide, Formoterol |
| Manufacturer | AbbVie | AstraZeneca |
| Class | Hormones and Birth Control | Respiratory Medications |
| Strengths | 25mcg, 50mcg, 75mcg, 100mcg, 150mcg | 80/4.5 mcg, 160/4.5 mcg, 200/6 mcg, 400/12 mcg |
| Forms | tablet | dry powder inhaler, metered-dose inhaler |
What's the same
Synthroid and Symbicort are used in very different patients, and the points in common are limited. The main shared element is that both meet regulatory standards for efficacy and safety and benefit from pharmacist oversight.
Key differences
Synthroid belongs to Hormones and Birth Control while Symbicort belongs to Respiratory Medications. Indications, mechanisms and target populations differ. The comparison is most useful when a clinician has mentioned both medications and the patient wants to understand where each fits.
Mechanism and action
Synthroid: Levothyroxine replaces deficient endogenous thyroxine, which is converted in tissues to the active hormone triiodothyronine (T3) by deiodinase enzymes. Symbicort: Budesonide reduces chronic airway inflammation through glucocorticoid receptor activation, decreasing inflammatory cell recruitment and cytokine release.
When Synthroid is preferred
Synthroid is approved for hypothyroidism of any cause (Hashimoto thyroiditis, post-thyroidectomy, post-radioiodine, congenital), goitre and TSH suppression after differentiated thyroid cancer.
When Symbicort is preferred
Symbicort is approved in adults and adolescents from age 12 (younger in some markets) for the regular treatment of asthma when combination therapy of a long-acting beta-2 agonist and an inhaled corticosteroid is appropriate, and in some markets for symptom relief in COPD.
Frequently asked questions
Is Synthroid or Symbicort better? ▾
Synthroid and Symbicort are not interchangeable — they treat different conditions. Asking which is "better" is meaningful only when a clinician has weighed both for the same specific clinical scenario.
Can I switch from Synthroid to Symbicort? ▾
Switching between Synthroid and Symbicort is rarely an appropriate decision since they belong to different classes and treat different conditions. The real question is usually whether the diagnosis calls for one medication or the other — which the prescriber resolves.
Do Synthroid and Symbicort have the same side effects? ▾
No — they belong to different classes and have distinct side-effect profiles. Each medication has its own prescribing information.
More Synthroid comparisons
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.