Hello kishorebdb Welcome to HCM zapiz or clonazapam 0.5 mg is a mouth dissolving drug used in a number of cases like insomnia, in anxiety disorders, in depressive disorders and in a number of other diseases to induce sedation. It is of Benzodiazepine group and it is a comparatively safer drug with main risk is abuse potential which is very high in elderly. Over all risk of any adverse effect is higher in elderly, but so far at this doses clonazepam is least likely to cause development of swelling or edema on toes. Cause of edema in him is probably relative inactivity which cause edema. Also his Sodium and Potassium levels are low, which might be due to fluid retention. So as per my advise kindly advise him to put one or two pillows below his feet while in lying down position. A brief walk under supervision will also fasten recovery. And get his kindness functions checked as edema may be a warning sign. Hope I cleared your doubt. Take Care