...
2. Drugs may be low in stock, or ran out, so alternative may be needed.
3. Drugs may cause allergies, which may not be desired.
3. DOCTOR specifies usage of the drug.
...
2. Drugs may need to be administered immediately.
3. Drugs may be limited to a certain kind of usage, like tablets, unit must be tablets, route must be oral, etc.
4. Total quantity of drugs is usually determined by the usage and frequency (multiplied).
5. Special care is needed for cream, syrups, where units may be vague and total quantity must be entered manually.
6. In programs, drugs are given indefinite amount, which should be another journey, not to be mixed with normal case.
4. DOCTOR repeatedly adds more drugs.
...