Briefly describe the advantages and disadvantages of sustained and controlled release preparations.

A: Advantages: ① For drugs with short half-life or requiring frequent administration, it can reduce the frequency of taking drugs and improve the compliance of patients. (2) Make the blood drug concentration stable, avoid the peak-valley phenomenon, and help to reduce the toxic and side effects of drugs. (3) The total dose can be reduced, so the maximum curative effect can be achieved with the minimum dose. Disadvantages: ① the flexibility of dose adjustment in clinical application is reduced; (2) When the pharmacokinetic characteristics of drugs change in the disease state, the dosage regimen cannot be flexibly adjusted; ③ The equipment and process cost involved in preparation are more expensive than that of conventional preparation.

Advantages: ① For drugs with short half-life or requiring frequent administration, it can reduce the times of taking drugs and improve the compliance of patients. (2) Make the blood drug concentration stable, avoid the peak-valley phenomenon, and help to reduce the toxic and side effects of drugs. ③ The total dose can be reduced, so the maximum drug effect can be achieved with the least dose. Disadvantages: ① the flexibility of dose adjustment in clinical application is reduced; (2) When the pharmacokinetic characteristics of drugs change in the disease state, the dosage regimen cannot be flexibly adjusted; ③ The equipment and process cost involved in preparation are more expensive than that of conventional preparation.