Samsca Dosage/Direction for Use

Usual Dosage in Adults: Patients should be in a hospital for initiation and re-initiation of therapy to evaluate the therapeutic response and because too rapid correction of hyponatremia can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma and death.
The usual starting dose for SAMSCA is 15 mg administered once daily without regard to meals. Increase the dose to 30 mg once daily, after at least 24 hours, to a maximum of 60 mg once daily, as needed to achieve the desired level of serum sodium. Do not administer SAMSCA for more than 30 days to minimize the risk of liver injury [see Liver Injury under Precautions].
During initiation and titration, frequently monitor for changes in serum electrolytes and volume. Avoid fluid restriction during the first 24 hours of therapy. Patients receiving SAMSCA should be advised that they can continue ingestion of fluid in response to thirst [see Too Rapid Correction of Serum Sodium Can Cause Serious Neurologic Sequelae (see Warnings) under Precautions].
Drug Withdrawal: Following discontinuation from SAMSCA, patients should be advised to resume fluid restriction and should be monitored for changes in serum sodium and volume status.
Co-Administration with CYP 3A Inhibitors, CYP 3A Inducers and P-gp Inhibitors: CYP 3A Inhibitors: Tolvaptan is metabolized by CYP 3A, and use with strong CYP 3A inhibitors causes a marked (5-fold) increase in exposure [see Concomitant use of strong CYP 3A inhibitors under Contraindications]. The effect of moderate CYP 3A inhibitors on tolvaptan exposure has not been assessed. Avoid co-administration of SAMSCA and moderate CYP 3A inhibitors [see Drug Interactions under Precautions, Effects of Drugs on Tolvaptan under Interactions].
CYP 3A Inducers: Co-administration of SAMSCA with potent CYP 3A inducers (e.g., rifampin) reduces tolvaptan plasma concentrations by 85%. Therefore, the expected clinical effects of SAMSCA may not be observed at the recommended dose. Patient response should be monitored and the dose adjusted accordingly [see Drug Interactions under Precautions, Effects of Drugs on Tolvaptan under Interactions].
P-gp Inhibitors: Tolvaptan is a substrate of P-gp. Co-administration of SAMSCA with inhibitors of P-gp (e.g., cyclosporine) may necessitate a decrease in SAMSCA dose [see Drug Interactions under Precautions, Effects of Drugs on Tolvaptan under Interactions].