Synthroid vs Prozac: side-by-side comparison
Synthroid (Hormones and Birth Control) and Prozac (Anti-Depressants) 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 | Prozac |
|---|---|---|
| Active ingredient | Levothyroxine | Fluoxetine |
| Manufacturer | AbbVie | Eli Lilly |
| Class | Hormones and Birth Control | Anti-Depressants |
| Strengths | 25mcg, 50mcg, 75mcg, 100mcg, 150mcg | 10mg, 20mg, 40mg |
| Forms | tablet | capsule, tablet |
What's the same
Synthroid and Prozac 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 Prozac belongs to Anti-Depressants. 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. Prozac: Fluoxetine selectively inhibits the serotonin reuptake transporter, increasing synaptic serotonin availability.
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 Prozac is preferred
Prozac is approved for major depressive disorder (adult and paediatric from age 8), obsessive-compulsive disorder (paediatric from age 7), bulimia nervosa, panic disorder and premenstrual dysphoric disorder.
Frequently asked questions
Is Synthroid or Prozac better? ▾
Synthroid and Prozac 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 Prozac? ▾
Switching between Synthroid and Prozac 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 Prozac 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.