Pulsed drug delivery(PDD),which can be released at well-defined time points as the therapy needs,can decrease the frequency and avoid taking drug at night,thus improving patient compliance.Here we introduce three kinds of programmed PDD systems independent of external chemical triggering;they are divided according to the triggering mechanisms:degradation-triggered PDD,osmotic pressure-triggered PDD,and both degradationi and osmotic pressure-triggered PDD.This paper reviews preparing technique,release mechanisms and influencing factors of the three PDD systems.The release profiles of pulsatile PDD can be regulated for different therapeutic needs,requiring no external triggers;especially that the PDD system triggered by both degradation and osmotic pressure has a bright future.

Objective To compare the change of mineral element in Tibet herb Halenia ellipitica D. Don before and after the seeds matured. Method We separately collected the cultivated Halenia ellipitica D. Don of several different districts in Qinghai province before and after the seeds matured and analyzed the contents of mineral elements as potassium, sodium, calcium, magnesium by atom absorb spectrum instrument. Results and Conclusion The calcium, magnesium and potassium, sodium elements nutriment has an antagonistic characteristic. The sodium and phosphorus elements nutriment has a coordination characteristic of the cultivated Halenia ellipitica D. Don in Qinghai province during the growth period.