Where, as above, C is annuity payment, PV is principal, n is number of payments, starting at end of first period, and i is interest rate per period. Equivalently C is the periodic loan repayment for a loan of PV extending over n periods at interest rate, i.
Refractory epilepsy is a seizure disorder that resists drug treatment. There is some debate among clinicians and researchers about how to define refractory epilepsy. As a result, this term is used in a variety of ways, and when a patient's epilepsy is described as refractory, resistant, or nonresponsive, it can be advisable to ask for more detail about what the diagnosis means.
In hypervolemic patients, in whom hyponatremia is due to renal sodium retention (eg, heart failure, cirrhosis, nephrotic syndrome) and dilution, water restriction combined with treatment of the underlying disorder is required. In patients with heart failure, an ACE inhibitor, in conjunction with a loop diuretic, can correct refractory hyponatremia.