You may need to deploy different strategies in order to use the room effectively. This might be using it on an ad-hoc basis or using an appointment system for services. This can be done simply using a diary, and scheduling appointments for medication reviews, for example, or for vaccinations.
If the appointments are booked in advance, a follow-up call/text the day before as a reminder to patients can help to confirm that they will arrive for their appointment. Having such services scheduled in gives a guaranteed income stream for that period of time.
However, if the pharmacy has only the one room, you may need to consider where in the pharmacy patients can be taken for a confidential conversation. The opportunity for an ad-hoc service would be reduced in those times, so having appointments at quieter times might be sensible.