Hello Jazz94 and thanks for posting us a question,

I am sorry to learn about your dad and the situation you find yourself in just now.  I can appreciate how difficult this must be.

I can't list them all, but certain medicines can react with alcohol. There are various effects that can happen for example increasing the risk of low blood pressure, liver damage and importantly slowing brain activity which in turn can make people more drowsy, less co-ordinated and 'with it'.  The British National Formulary lists the known interactions of alcohol with medicines at this link. 

Heavy drinking poses a health risk in itself, see what the NHS website says about it here, and mixing alcohol and strong pain killers like morphine can be dangerous, so the advice is not to drink alcohol at all while taking them - alcohol can enhance the sedating effects.  The dangers could be things like falling over, having an accident, forgetting to do things that are important like taking medicines and drinking enough fluids and in extreme cases heart and breathing rates might be affected.

I don't know if your dad's doctors and nurses are aware of his drinking behaviour, I think they need to know. Doctors and nurses can't discuss someone's medical care without their permission, but anyone can make a concern known. So you could contact the chemotherapy clinic where your dad is being treated and his GP, if you know who they are, to explain your concerns.

You can also tell your father of the risks. All medicines have a patient leaflet with instructions about how to take them so you can refer him to those. But I don't know if he will take what you say on board. The local pharmacist may also be able to help with advice.   

When cancers travel to the brain, they can sometimes cause a change in behaviour, I am not sure if this is a factor in what is going on.

You probably already know about the organisation AL-Anon which offers support to people affected by someone else's drinking. 

Please give us a ring if you want to talk anything over, the number to call is Freephone 0808 800 4040 and we are here weekdays, 9-5.

Best wishes,

Julia

So sorry about your Dad jazz, I'm 29 and I share an experience with you.
 

My mum has a heavy nicotine addiction and is a drinker and smoker always has been

Not only smoking 10-20 a day but she even chews nictotine gum when she's not smoking... refuses to try vaping as an alternative..

My mum has had breast cancer and she continued through all of her therapy whilst drinking wine. No regrets at all from her and I wasn't qualified to judge, or was I going to dictate how to live her life,  she is also stubborn, she said the doctors said it would be okay.

 Symptoms

But I'll be honest and say my mom has either  Alcoholic Neuropathy or Dyphasia (Speech Impared) 12 months or 1.5 years in the future from her treatment, after one or two wine glasses it's difficult to understand my mom and this has also affected her speech when she's not even drinking, sometimes indecipherable and it's ruined her confidence, no way can she order drinks at a bar or edge into any conversation really.

I've been Googling and doing researching what drugs she is taking post treatment (all clear) what are and the side effects etc, and I'm sure it's best without achohol mixed.. I really want to find out if she can improve her health by stopping , she has been through a lot and she continues to drink and ignore me I am trying really hard with my sister. In fact we're going private to skip nhs waiting times so we can get a proper diagnosis from a neurologist.
 

Speech issues example 

Example: She said  two words that weren't easy to understand phonetically, then wrote it out perfectly on the iPad, all she said was something more complex than it sounded like 'Anything that is mine, you can use what you like x' in reference  to anything in the hotel room where I am tonight with her.
 

For the moment I can understand her, and in the day somewhat and sometimes we have to ask her to repeat what she said, but my mum isn't the same as before her treatment,  her beautiful motherly actions are who she has always been though, it's mainly a communication problem  now, but we don't know how much it's been hurting her inside, and it's also affected her hugely mentally, blew up her world and she turns to self abuse, my poor mum and anyone who gets cancer and struggles with addiction  , I hate to see her go through this frustration of not being able to socialise properly after beating a diesese such as cancer and being glad to have came out the other side to continue to enjoy life.

Further more about her speech, she gets angry and shouts when we can't understand her, I really do try and I understand the majority of the time, but I really have to concentrate and repeice the closest word I thought it was for a whole sentence to get it what she means,  but other times it really isn't possible to understand at all without her typing it out, especially after if she drinks alchohol, even just 2 glasses or perhaps when she is sleepy too.
 

It breaks my heart honestly, but I'm doing all I can to help her, I want to find out if it's reversable, but she's angry that when I say something about stopping drinking and she raises her voice "Don't lecture me!", "Don't dictate to me", we have had words today and we're looking at solutions after holiday. I want her to enjoy the time while she's here and I don't want her to accelerate her death, i said we won't talk any more about this until we've back home from holiday.

She is a business owner through all of this and provides care to elderly and disabled, she is an absolute solider and I couldn't be more proud of her, I love my mom she is the best lady in the world to me. But sometimes I feel she doesn't love her self or care for her self as much anymore.

Hello and thank you for posting.

I know you haven't posted a question for the nurses to answer, but I wanted to acknowledge your post. You are obviously going through a very difficult time with your mum so I hope you are taking good care of yourself.

I hope you know more about what is happening with your mum soon.

Sarah.