Plasma salicylic acid concentrations should be periodically monitored during long-term treatment with salsalate to aid maintenance of therapeutically effective levels: 10 to 30 mg/100 ml. Toxic manifestations are not usually seen until plasma concentrations exceed 30 mg/100 ml (see OVERDOSAGE). Urinary pH should also be regularly monitored: sudden acidification, as from pH 6.5 to 5.5, can double the plasma level, resulting in toxicity.
Because serious GI tract ulcerations and bleeding can occur without warning symptoms, physicians should monitor for signs or symptoms of GI bleeding. Patients on long-term treatment with NSAIDs, should have their CBC and a chemistry profile checked periodically. If clinical signs and symptoms consistent with liver or renal disease develop, systemic manifestations occur (e.g., eosinophilia, rash, etc.) or if abnormal liver tests persist or worsen, Salsalate tablet, USP should be discontinued.
Reports suggest that NSAIDs may diminish the antihypertensive effect of ACE-inhibitors. This interaction should be given consideration in patients taking NSAIDs concomitantly with ACE-inhibitors.
Salicylates antagonize the uricosuric action of drugs used to treat gout. ASPIRIN AND OTHER SALICYLATE DRUGS WILL BE ADDITIVE TO SALSALATE AND MAY INCREASE PLASMA CONCENTRATIONS OF SALICYLIC ACID TO TOXIC LEVELS. Drugs and foods that raise urine pH will increase renal clearance and urinary excretion of salicylic acid, thus lowering plasma levels: acidifying drugs or foods will decrease urinary excretion and increase plasma levels. Salicylates given concomitantly with anticoagulant drugs may predispose to systemic bleeding.
Salicylates may enhance the hypoglycemic effect of oral antidiabetic drugs of the sulfonylurea class. Salicylate competes with a number of drugs for protein binding sites, notably penicillin, thiopental, thyroxine, triiodothyronine, phenytoin, sulfinpyrazone, naproxen, warfarin, methotrexate, and possibly corticosteroids.
[When Salsalate tablet, USP is administered with aspirin, its protein binding is reduced, although the clearance of free Salsalate tablet, USP is not altered. The clinical significance of this interaction is not known; however,] as with other NSAIDs, concomitant administration of salsalate and aspirin is not generally recommended because of the potential of increased adverse effects.
Clinical studies, as well as post marketing observations, have shown that Salsalate tablet, USP can reduce the natriuretic effect-of furosemide and thiazides in some patients. This response has been attributed to inhibition of renal prostaglandin synthesis. During concomitant therapy with NSAIDs, the patient should be observed closely for signs of renal failure (see PRECAUTIONS, Renal Effects), as well as to assure diuretic efficacy.
NSAIDs have produced an elevation of plasma lithium levels and a reduction in renal lithium clearance. The mean minimum lithium concentration increased 15% and the renal clearance was decreased by approximately 20%. These effects have been attributed to inhibition of renal prostaglandin synthesis by the NSAID. Thus, when NSAIDs and lithium are administered concurrently, subjects should be observed carefully for signs of lithium toxicity.
NSAIDs have been reported to competitively inhibit methotrexate accumulation in rabbit kidney slices. This may indicate that they could enhance the toxicity of methotrexate. Caution should be used when NSAIDs are administered concomitantly with methotrexate.
The effects of warfarin and NSAIDs on GI bleeding are synergistic, such that users of both drugs together have a risk of serious GI bleeding higher than users of either drug alone.
Salicylate competes with thyroid hormone for binding to plasma proteins, which may be reflected in a depressed plasma T4 value in some patients; thyroid function and basal metabolism are unaffected.
No long-term animal studies have been performed with salsalate to evaluate its carcinogenic potential.
Reproductive studies conducted in rats and rabbits have not demonstrated evidence of developmental abnormalities. However, animal reproduction studies are not always predictive of human response. There are no adequate and well-controlled studies in pregnant women.
Because of the known effects of nonsteroidal anti-inflammatory drugs on the fetal cardiovascular system (closure of ductus arteriosus), use during pregnancy (particularly late pregnancy) should be avoided.
There exist no adequate and well-controlled studies in pregnant women. Although adverse effects on mother or infant have not been reported with salsalate use during labor, caution is advised when anti-inflammatory dosage is involved. However, other salicylates have been associated with prolonged gestation and labor, maternal and neonatal bleeding sequelae, potentiation of narcotic and barbiturate effects (respiratory or cardiac arrest in the mother), delivery problems and stillbirth.
In rat studies with NSAIDs, as with other drugs known to inhibit prostaglandin synthesis, an increased incidence of dystocia, delayed parturition, and decreased pup survival occurred. The effects of Salsalate tablet, USP on labor and delivery in pregnant women are unknown.
It is not known whether salsalate per se is excreted in human milk; salicylic acid, the primary metabolite of salsalate, has been shown to appear in human milk in concentrations approximating the maternal blood level. Thus, the infant of a mother on salsalate therapy might ingest in mother’s milk 30 to 80% as much salicylate per kg body weight as the mother is taking. Accordingly, caution should be exercised when salsalate is administered to a nursing woman.
Safety and effectiveness of salsalate use in children have not been established. (See WARNINGS section.)
As with any NSAIDs, caution should be exercised in treating the elderly (65 years and older).
In two well-controlled clinical trials, the following reversible adverse experiences characteristic of salicylates were most commonly reported with salsalate (n-280 pts; listed in descending order of frequency): tinnitus, nausea, hearing impairment, rash, and vertigo. These common symptoms of salicylates, i.e., tinnitus or reversible hearing impairment, are often used as a guide to therapy.
Although cause-and-effect relationships have not been established, spontaneous reports over a ten-year period have included the following additional medically significant adverse experiences: abdominal pain, abnormal hepatic function, anaphylactic shock, angioedema, bronchospasm, decreased creatinine clearance, diarrhea, G.I. bleeding, hepatitis, hypotension, nephritis and urticaria.
Drug abuse and dependence have not been reported with salsalate.
Death has followed ingestion of 10 to 30 g of salicylates in adults, but much larger amounts have been ingested without fatal outcome.
The usual symptoms of salicylism tinnitus, vertigo, headache, confusion, drowsiness, sweating, hyperventilation, vomiting and diarrhea will occur. More severe intoxication will lead to disruption of electrolyte balance and blood pH, and hyperthermia and dehydration.
Further absorption of salsalate from the G.I. tract should be prevented by emesis (syrup of ipecac), and, if necessary, by gastric lavage.
Fluid and electrolyte imbalance should be corrected by the administration of appropriate I.V. therapy. Adequate renal function should be maintained. Hemodialysis or peritoneal dialysis may be required in extreme cases.
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