Welcome to HCM,
Your father is diabetic and Hypertensive taking oral hypoglycaemic drugs ( Zoryl M) and Telmicheck 40 mg, I presume his BP and blood sugar is well controlled.
BPH or prostate enlargement is common problem of this age as it is mild drug alpha blocker
is given which relaxes the lower urinary bladder
to allow emptying of bladder.
This drug is for continuous use and side effects are not very common but we must rule out prostate cancer
by proper tests.Mild nausea
,GI up set may occur.
Postural hypo tension dizziness
can occur,allergic reactions like rash, itching,Abnormal ejaculation, decrease in sexual activities
Please let him take the medicine if he feels any thing please report to treating doctor