Jay:  If this mother is having minimal coughing and is sleeping well, and
she doesn't feel the need to take this medication, then what's the
problem?  This medication is purely for symptomatic relief, so if her
symptoms are not so bad, why take it? I am very curious about why her
doctor is so insistent on her taking it.  This is not the same situation
as someone who has a bacterial infection and must take the antibiotic to
cure it.
As for your question re the meds listed: promethazine is not only used
for nausea and motion sickness, but it is an antihistamine and therefore
helps with allergic symptoms.  It's the codeine which is a cough
suppressant, but codeine can be used alone for this purpose (though I
doubt that this lady needs cough suppression anyway).  If her cough is
due to asthma, she would probably be better off using an inhaler such as
albuterol.  Hope this helps.  Alicia.  [log in to unmask]