Salsalate, is a nonsteroidal anti-inflammatory agent for oral administration. Chemically, salsalate (salicylsalicylic acid or 2-hydroxy-benzoic acid, 2- carboxyphenyl ester) is a dimer of salicylic acid; its structural formula is shown below.
Each tablet, for oral administration contains 500 mg or 750 mg of salsalate, USP. In addition each tablet contains the following inactive ingredients: Microcrystalline Cellulose, Sodium Starch Glycolate, Povidone, and Stearic Acid. Also contains: Hydroxypropyl Methylcellulose, Polydextrose, Titanium Dioxide, Triacetin, FD&C Blue No. 1 Aluminum Lake, FD&C Blue No. 2 Aluminum Lake and Polyethylene Glycol.
Salsalate is insoluble in acid gastric fluids (<0.1 mg/ml at pH 1.0), but readily soluble in the small intestine where it is partially hydrolyzed to two molecules of salicylic acid. A significant portion of the parent compound is absorbed unchanged and undergoes rapid esterase hydrolysis in the body: its half-life is about one hour. About 13% is excreted through the kidneys as a glucuronide conjugate of the parent compound, the remainder as salicylic acid and its metabolites. Thus, the amount of salicylic acid available from salsalate is about 15% less than from aspirin, when the two drugs are administered on a salicylic acid molar equivalent basis (3.6 g salsalate/5 g aspirin). Salicylic acid biotransformation is saturated at anti-inflammatory doses of salsalate. Such capacity-limited biotransformation results in an increase in the half-life of salicylic acid from 3.5 to 16 or more hours. Thus, dosing with salsalate twice a day will satisfactorily maintain blood levels within the desired therapeutic range (10 to 30 mg/100 ml) throughout the 12-hour intervals. Therapeutic blood levels continue for up to 16 hours after the last dose. The parent compound does not show capacity-limited biotransformation, nor does it accumulate in the plasma on multiple dosing. Food slows the absorption of all salicylates including salsalate.
The mode of anti-inflammatory action of salsalate and other nonsteroidal anti-inflammatory drugs is not fully defined. Although salicylic acid (the primary metabolite of salsalate) is a weak inhibitor of prostaglandin synthesis in vitro, salsalate appears to selectively inhibit prostaglandin synthesis in vivo
1, providing anti-inflammatory activity equivalent to aspirin2 and indomethacin3. Unlike aspirin, salsalate does not inhibit platelet aggregation4.
The usefulness of salicylic acid, the active in vivo product of salsalate, in the treatment of arthritic disorders has been established 5,6. In contrast to aspirin, salsalate causes no greater fecal gastrointestinal blood loss than placebo7.