Follow the VED analysis (Vital, Essential, Desirable). This will help to control Inventory in a store of pharmaceutical industry. I have described about VED in your previous question.
Inventory control which is an integral part of Supply Chain System/Logistic Cycle would help you to know;
1. How long your stock would last, the most important unit in inventory control is month of stock (MOS) which is the ratio of Stock on hand (SOH) to average monthly consumption (AMC).
2. It assist you to know whether your stock is within a plausible pre-determined range in Minimum-Maximum (Min-Max) Inventory control system. There are systematic methods of determine the min-max using parameters such as suppliers lead time, buffer stock, adopted inventory control system etc.
3. It also assist in budgeting as mentioned by other contributor. After evidence based selection of products to be purchased, quantification is carried out usually based on consumption data with appropriate adjustment for annual incremental growth in service delivery capacity. Cost implication is determined using facts from quantification and unit cost of each items taking the pack size and the various specifications into consideration, a budget-gap analysis may be needed particularly if fund is inadequate.
4. Inventory monitoring also assists in managing your storage capacity effectively so that ordered quantities of products are not in excess of available space.
5. Closely related to the first point, it helps you to know the require quantity to order taking yet to be supplied ordered stock into consideration.
6. Most importantly, inventory control helps in ensuring Customer Satisfaction, the bed rock of sustainability.