From your question it appears that your fathers disease started 3 months back.
It is very unlikely for someone to get asthma at 73 years of age.
If your father developed breathlessness and cough 3 months back , the possibilities are pulmonary oedema
( cardiac failure ) or COPD ( chronic obstructive pulmonary disease
Regarding safety of the medicines
Theoasthalin - many patients in India are taking it for decades
possible side effects -- tremor , increased heart rate
, acidity, low potassiumin blood( can lead to muscle cramps
Deflozacort - It is a steroid and long term usage is avoided as far as possible. However do not stop it abruptly.
As your father is 73 year old and been taking it for 3 months , its dose will have to reduced gradually to stop. But in some patients long term usage at lowest possible dose will be required.
possible side effects - diabetes , hypertension
, acidity, ulcer , weak bones, puffiness of face , fungal infections , glaucoma , cataractDiltiazem
- is usually tolerated in long term use
possible side effects - edema , dizziness
Discuss with your doctor regarding changing from defcort to alternatives like metered dose inhaler with spacer