Thioamide

Thioamides (rarely, thionamide) are a group of organic compounds that share a common functional group with the general structure R1-CS-NR2R3. One of the best ways of making thioamides is the reaction of an amide with Lawesson's reagent.

Thioamides are also a class of drugs which are used to control thyrotoxicosis.

Incorporation of thioamides into peptides are used as isosters for the amide bond. Peptide modifications are interesting analogoues of the native peptide, which can reveal the structure-activity-relationship (SAR). Analogoues of peptides can also be used as drugs with an improved oral bioavailability.

Mechanism of action
They inhibit the enzyme thyroid peroxidase in the thyroid, reducing the synthesis of triiodothyronine (T3) and thyroxine (T4); block uptake of iodotyrosines from the colloid. They also block iodine release from peripheral hormone. Maximum effects occur only after a month since hormone depletion is caused by reduced synthesis, which is a slow process.

Adverse effects
It penetrates the placental barrier, thus caution is advised when used during pregnancy.

10% of patients report:
 * Skin eruptions, such as macules and papules.
 * Urticaria
 * Dermatitis
 * Fever
 * Arthralgia

0.03% of all patients develop agranulocytosis, a dangerous side-effect.

Members of the thioamide group

 * Methimazole
 * Carbimazole converted in vivo to methimazole
 * Propylthiouracil

チオアミド Tioamida