A client who has chronic bronchial asthma has had a mast cell stabilizer prescribed.
What drug would the provider prescribe?

Levothyroxine is a synthetic form of thyroxine, the hormone that the thyroid gland normally produces.It is used to treat hypothyroidism by replacing the missing hormone and restoring the normal metabolism.

Some explanations for the other choices are:

• Choice B. Thyroid desiccated is a natural thyroid hormone derived from animal thyroid glands.

It contains both T4 and T3 hormones, which may cause side effects or complications in some people with hypothyroidism.It is not recommended as a first-line treatment for hypothyroidism.

• Choice C. Methimazole is an antithyroid drug that blocks the production of thyroid hormones.

It is used to treat hyperthyroidism, not hypothyroidism.Giving methimazole to someone with hypothyroidism would worsen their condition.

• Choice D. Liothyronine is a synthetic form of T3, the active thyroid hormone.

It is sometimes used in combination with levothyroxine to treat hypothyroidism, but it is not a standard treatment.It has a shorter half-life and more variable effects than levothyroxine, and it may increase the risk of cardiac arrhythmias or osteoporosis.

Normal ranges for thyroid function tests vary depending on the laboratory and the method used, but generally they are:

• TSH: 0.4 to 4.0 mIU/L

• Free T4: 0.8 to 2.0 ng/dL

• Free T3: 2.3 to 4.2 pg/mL

Famotidine is a histamine type 2 receptor antagonist (H blocker) which is commonly used for treatment of acid-peptic disease and heartburn. Famotidine has been linked to rare instances of clinically apparent acute liver injury, but it is less likely to cause hepatotoxicity than cimetidine, another H blocker. Famotidine also has fewer drug interactions than cimetidine.

Choice A is wrong because nizatidine is another H blocker that can cause mild and transient serum aminotransferase elevations.

Nizatidine has not been linked to cases of clinically apparent liver injury, but it has not been widely used.

Choice B is wrong because ranitidine is another H blocker that can cause mild and transient serum aminotransferase elevations.

Ranitidine has also been associated with rare instances of clinically apparent liver injury, some of which were fatal or required liver transplantation.

Choice C is wrong because cimetidine is another H blocker that can cause mild and transient serum aminotransferase elevations.

Cimetidine has also been implicated in several cases of clinically apparent acute liver injury, some of which were severe and led to acute liver failure and death.

Cimetidine also has many drug interactions due to its inhibition of cytochrome P enzymes.

Normal ranges for serum aminotransferases are 7 to 56 U/L for alanine aminotransferase (ALT) and 10 to 40 U/L for as