Hello
Your mother is having 'dry cough" , for this advised doxophylin 400 mg twice in day .
First of all note down the side effects of "doxophyllin" , so that you understand something.
Nausea ,
vomiting,
anxiety confusion , fine tremors particularly in hands , seizures , hyperglycaemia .
As you mentioned that your mother is showing some abnormal behaviour , reason may be .
1&2 Due to confusion ( side effect of drug ) she may have such type of symptoms.
3 Stomach problem is due to side effect of this drug ( this is common).
Still your mother would have to take this drug for 4 days , so if there is relief in dry cough then continue this drug for four days more.
If no relief in dry cough then consult a physician and get his opinion.
Stop drug after 4 days and still these symptoms present then
consult psychiatrist and get his opinion.
Hope this information will be helpful for you.