Abstract
The dissolution characteristics of two sustained-release preparations widely used in Japan, one taken twice-a-day (Theodur® tablet) and one taken once-a-day (Uniphy® tablet), were examined.
Both preparations showed a near zero order release and the rates were almost equal in pH 1.2, but a deifference was observed in the two preparations regarding pH 6.8. When influences due to halving of the tablets and changes in the rotative number of the basket were examined in pH 6.8, the Uniphyl® tablet was found to be less influenced than the Theodur® tablet.
The maintenance time of the effective concentration of these two preparations was predicted based on the absorption profiles in six volunteers and the elimination of several diseases on reference. Although the Uniphyl® tablet showed a remarkable susutained-release effect, the time to peak (Tmax) tended to appear early and the maximum concentration (Cmax, ) was significantly lower than that of the Theodur® tablet. However, there was no difference in the area under the salivary concentration curve up to infinity time.
If circadian rhythms are not taken into consideration, the administration of either a Theodur® or Uniphyl® tablet once-a-day should fully prevent a morning dip even in cases of enhanced elimination such as in hyperthyroid patients. On the other hand, for cirrhosis patients, these results suggest that even tablets normally taken twice-a-day can be taken once-a-day for Round The Clock (RTC) therapy.
