The gelform has a longer residence time on the eye surface and so has a sustained effect, meaning administration can be once a day instead of twice a day. The gel is also less likely to reach the nasolacrimal duct and cause systemic effects. Topical beta-blockers, which ideally should only be absorbed directly into the eye, are also absorbed via the nasolacrimal system into the nasal and oral mucosa and so enter the bloodstream direct, bypassing the liver. (4)
It is this undesirable ‘detour’ of the drug that can cause the many and potentially serious side-effects, especially in patients with certain existing health conditions. Patients may not readily associate any such health changes with the eye drops they are using. Certain sub-classes of beta-blocking eye drops can lower blood pressure and heart rate, sometimes severely (bradycardia) and more so in susceptible individuals. Therefore, there may be a contra-indication to their use, but occasionally this occurs in otherwise healthy people too.