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SAR 1118 Ophthalmic Solution appears safe and well-tolerated up to 5.0% TID in healthy adult subjects. PK analysis shows adequate ocular exposure with minimal systemic exposure.

The pharmacokinetics and bioavailability of total (bound plus unbound) and unbound disopyramide were compared following the simultaneous administration of an oral dose of disopyramide and an intravenous dose of 14C-disopyramide in five normal volunteers and in 11 patients with congestive heart failure. The binding of disopyramide varied between 60 and 92% in patients and between 81 and 88% in normal subjects at postequilibrium drug concentrations of 10(-7) M. The binding of disopyramide to serum protein was concentration-dependent in all study subjects at serum concentrations achieved following drug administration. The association constant for the first binding site in serum from normal subjects and patients averaged 8.7 X 10(5) M-1 and 4.4 X 10(5) M-1, respectively (p less than 0.05). The unbound clearance of disopyramide averaged 277 ml/min and 209 ml/min in normal subjects and in patients (p less than 0.05). When normalized for body weight, the unbound clearance between patients and normal subjects was not significantly different. The elimination half-life of unbound concentrations in normal subjects and in patients averaged 4.9 and 6.1 h, respectively (p less than 0.05). The clearance and elimination half-life of total disopyramide was the same in both groups. Although the bioavailability of disopyramide averaged 0.85 in both groups, it was more variable in patients owing to the variability in the fraction of the dose absorbed. The unbound renal clearance and volume of distribution at steady state of disopyramide was related to cardiac index. The ratio of elimination half-lives of total and unbound disopyramide was related to the extent of serum protein binding.

A rapid ultrafiltration technique was used to measure the free (unbound) fraction of disopyramide in serum obtained from 14 normal volunteers, 6 chronic hemodialysis patients, and 10 renal transplant recipients. The disopyramide-free fraction varied more than tenfold at a corresponding total (free plus bound) serum disopyramide concentration of 3 μg/ml and was related to the concentration of an acute-phase protein, alpha-1 -acid glycoprotein (AAG), in patient serum. Moreover, disopyramide-free fraction values were nearly twofold lower than normal in serum specimens obtained from those renal patients and transplant recipients with corresponding AAG serum concentrations greater than 100 mg/l00 ml. AAG concentrations varied tenfold in patient serum and were on average nearly three times higher than AAG concentrations in normal volunteer serum. These findings suggested that the free fraction of disopyramide and possibly other drugs which bind extensively to AAG may be lower, and the interpatient variability in drug binding may be much more pronounced in serum obtained from hemodialysis patients and transplant recipients than previously recognized.