Hi Mich and thanks for posting.

I'm sorry to hear about your dad.

Unfortunately, most over the counter products won't be effective for a persistent cough associated with a lung cancer diagnosis.  Some prescription medications can be helpful for this.  You could contact your dad's GP, or does he have a specialist nurse that you could ask?  Some areas have teams who help with symptom control, your specialist nurse should know more about this and could put you in touch with them.

It is possible your dad might have a chest infection if he is more breathless than usual and is coughing up coloured phlegm or has a temperature. People with lung cancer can be more prone to infections.   A course of antibiotics can be given to clear up the infection if he has one.  It sounds like it would be good to talk to his GP or lung cancer specialist nurse.  They will be able to examine him and decide whether he does need antibiotics. 

There is some information here about managing the symptoms of lung cancer which you may find useful.

We also have some information about coping with cancer here which has sections for friends and family, as well as ways to cope physically, and emotionally.

I hope that this is helpful.  We also have a nurse helpline.  You can call on Freephone 0808 800 4040 and the lines are open from 9am till 5pm Monday to Friday.

Take care

Rachel