## 8 Conclusions  
This paper describes a multiproduct inventory control problem in a pharmaceutical distribution company, modelled as a corresponding dynamic discrete-time system control process. The actuality of the topic elaborated in the paper is consistent with the importance of the pharmaceutical inventory and distribution management. The improvement of the mentioned processes management in pharmaceutical companies implies cost reduction and customer service level improvements. The paper is aimed at the development of an inventory control model for a pharmaceutical distribution company, with an emphasis on reorder quantities and reorder periods, and the satisfaction of specific constraints. The mathematical model is based on the proposed conceptual model, developed in accordance with the modern control theory concept and specific practical assumptions and constraints of the supply chain, as noticed in the company. The authors proposed two variations of the model, implemented in the spreadsheet environment of MS Excel and automated through Visual Basic for Applications. The model allows analysis from many different perspectives and can be easily modified and enhanced in order to reflect new scenarios. The developed model represents a baseline model that enables the creation of alternative scenarios and comparison of those scenarios to the baseline. Furthermore, the presented solution of the problem satisfies the request defined by the company which is related to the affordable but dynamic and flexible software solution that is relatively easy to implement and use. These contributions, detailed in the paper, represent an important aspect of managerial implications. The theoretical contribution and some of the main advantages of the developed control model concerning the traditional DRP model are:  
* FOQ- and LFL-based models determine lot size and safety stock. * These models recalculate order quantities and reorder points if demand is changed in real-time. * The full automation of the model is based on the concept of feedback control. * The structure of the model is precisely defined according to the object of discrete control with an adequate mathematical apparatus. In order to emphasize specificities of the research presented in this paper, and at the same time the improvements of the previous study mentioned in [15], the authors of the paper point out the following contributions:  
* Modern control theory (MCT), i.e., self-regulation and feedback control concepts, with relevant elements (sensor, comparator, controller, system) of the feedback loop are applied during the development of the conceptual model. * The mathematical model presented in the paper is comprised of two flows. The planned inventory state represents information flow, while the actual inventory state refers to material flow. Each flow has one phase of accumulation and two phases of action. Two sales variables and two inventory state variables, planned and realized, are precisely mathematically defined, with their mutual influence, i.e., the impact of the actual state of inventory on the future, and the planned inventory state. * The performance criterion of the inventory system is defined and described through two objective functions, the maximization of the difference between the planned average inventory level and the realized average inventory level and the minimization of the number of stock-out situations. * The originally developed comparison algorithm for the planned order quantity reflects the decision tree for comparison of all relevant stock variables. * Sensitivity analysis is conducted, and numerical results are explained clearly with all supporting data. * Stochastic demand is generated as a random variation of sales forecast in the range of \(\pm 20\%\). Numerical results are compared for deterministic and stochastic actual sales. The applicability of the model has been proven by its usage for procurement planning in the described company within the period of two years.