Galenic compatibility and plausibility checks made easy –
with the Formula Fan developed by

Plausibility checks are one of the most important tasks in preparing pharmaceuticals according to individual formulas in the pharmacy. The chemical and physical compatibility of primary substances must be taken into account. For a long time, huge, confusing tables in DIN-A1 format were used which were difficult to handle.

Our task was simply to develop something better. Information on compatibility including qualities and solubilities needed to be presented for 79 primary substances. Manageability, clear overviews, and hygiene were the most relevant specifications. It needed to be a useful tool that made preparing individual formulas much easier for pharmacists and PTAs. With the Caelo formula fans, we created and successfully instituted such a tool for our client Caelo.

Job: Develop a tool to evaluate compatibility and carry out plausibility testing when producing individual pharmaceuticals

Client: Caelo Caesar & Lorenz GmbH

Services: Product development, layout, production

Indication/topic: Galenic compatibility and plausibility testing for individual pharmaceuticals


For this product development assignment, we consistently applied the design thinking approach, which places the requirements and needs of the user in the center. We held practically-oriented workshops to work out the needs of users. The result? The formula tool needed to be a manageable size, clearly arranged, help prevent mistakes, and comply with hygiene standards in the production area of a pharmacy – and it needed to be produced at a moderate cost so that PTAs could afford it.

Based on these user requirements, we developed and constructed prototypes of three possible tools that met all these criteria.


We had pharmacists and PTAs with pharmaceutical production experience test the prototypes of the tools we developed. In the practical tests, the fan format we developed came out on top. In further tests, we jointly improved the product.

Caelo formula fans now present the information required for 79 primary substances: Compatibility, solubility, the recommended concentration, NRF (Neues Rezeptur-Formularium, new prescription formula) number, order numbers for basic agents und solvents, and ointment classifications. Thanks to the fan format, the information is quick and easy to read. The material is wipeable and therefore complies with strict hygiene standards.


Formula fans have not only become a standard tool in in-house pharmaceutical production and PTA training, but the term has become established in its own right. Caelo was cheered during the presentation of the first edition of this formula fan.

Now, the formula fan is in its fifth, updated and improved edition with over 30,000 copies and its own PZN (Pharmazentralnummer, central pharmaceutical number). With these fans, along with the website, Caelo provides an extremely practical, reliable formula service for pharmacies. Caelo formula fans can be ordered through pharmaceutical wholesalers with the number PZN 09944458 or directly from CAELO.