To understand the controlled release of drug molecules from zeolite hosts, we propose to study using INS the interactions of beta-blocker atenolol with the Brønsted acid sites in potential zeolite candidates for its controlled release, H-FAU (Si/Al=5), H-FAU(Si/Al=80) and zeolite beta. The H-FAU (5) sample releases the drug over a 24 hour period, whereas the H-FAU (80) sample releases over 10 days. This is counterintuitive as the much larger number of Brønsted acid sites in H-FAU (5) should slow the molecular mobility through interactions with the sorbate. QENS experiments (RB1710135) suggest that the fundamental freedom of mobility is indeed higher in the H-FAU (5) sample, and diffraction data suggests more lattice distortion upon drug adsorption in the slower releasing H-FAU (80) sample. We aim to rationalise these observations through probing sorbate-Brønsted site interactions.