Thyroid Medications: medications in this class

Overview

Levothyroxine, synthetic T4, is the standard treatment for an underactive thyroid: once daily on an empty stomach, dose set against the TSH blood test, for life. Liothyronine (T3) is added for a minority who do not feel well on T4 alone. Desiccated thyroid extracts, made from animal glands, contain both hormones in a fixed ratio and are used by some prescribers, though, unlike the synthetic products, they are not FDA-approved.

Methimazole and propylthiouracil treat an overactive thyroid by reducing hormone production; methimazole is preferred except in early pregnancy. Beta blockers are often added briefly to control symptoms while they take effect, although an overactive thyroid is not an FDA-approved use for them, so the prescriber decides.

Because the levothyroxine dose window is narrow, small differences between manufacturers can shift the TSH; many endocrinologists ask patients to stay on one maker and to re-check the TSH after any switch.

How the drugs in this class differ when you pay cash

Levothyroxine, liothyronine, methimazole and propylthiouracil are all available as generics. The decision for a cash-paying patient is about consistency as much as the quote: choose a pharmacy that can keep dispensing the same levothyroxine manufacturer, ask it to note that on your profile, and use ninety-day fills to reduce the chance of a switch. Brand levothyroxine (Synthroid, Levoxyl, Unithroid, Tirosint) is one way to stay on the same product; a generic from a pharmacy that can keep supplying one maker is another.

If you use a desiccated thyroid product, ask the pharmacy whether it can supply it before relying on a quote. Quotes for liothyronine, like any prescription, can differ between pharmacies.

Medicines at a glance

How the medicines in this group are supplied and usually taken. Each guide has the full details.

• Levothyroxine
  Tablets (Synthroid, Levoxyl, Unithroid and generic), Soft gel capsules (Tirosint), Oral solution in single-dose ampules (Tirosint-SOL)
  Generic: Yes · Once a day
• Liothyronine
  Tablets, Injection (hospital use)
  Generic: Yes · Once a day
• Methimazole
  Tablets (generic)
  Generic: Yes · Three times a day
• Propylthiouracil
  Tablets
  Generic: Yes · Three times a day

Medications

Which of these is right for a given person is a decision for the prescriber. The guides explain what each drug is, how it is supplied, and why its cash price varies between pharmacies. No page on this site shows a price; prices come from pharmacies responding to your actual prescription.

Questions worth asking

• Does my prescriber want me on one manufacturer, and can this pharmacy guarantee it?
• How should I time the dose around food, coffee, calcium and iron?
• When is my next TSH check, and should I have one after any switch?
• Is a ninety-day prescription appropriate?
• Which symptoms suggest my dose is too high or too low?