Hi
Thanks for choosing HCM for your query.
I appreciate your concern regarding the clearance time of 
Atenolol.
Approximately 50% of Atenolol is excreted in the urine within 24 hrs, remaining amount gets excreted in another 12 hours.
The newly prescribed combination of medicines 
Lisinopril and 
Diltiazem is effective in controlling the 
high BP. 
The new medicines will start acting soon which is reflected in the form of slight 
dizziness, palpitations, light headedness which are self limiting.
If these side effects persist, you are advised to visit your treating doctor for the correction of the doses.
Hope your query is being answered.
Kindly rate the answer if you are convinced.
Wishing you best of your health.