With regard to your first question on access to drugs - unfortunately there are few drugs available for treating ovarian cancer currently, so it's unlikely your wife is being denied anything that is available in other places. Have you had this discussion with your clinician? Is there a particular drug you've heard of that you'd like to know more about?
We'd recommend speaking to your clinician about options now and later, and also asking about what clinical trials are available for your wife to access. Remember you can always seek a second opinion if you do not feel you're getting answers from your clinician - you can ask your wife's GP or clinical nurse specialist to arrange this for you.
With regard to your second question about intraperitoneal chemotherapy,
NICE guidance does not recommend intra peritoneal therapy (IP therapy) outside of a trial. A recent UK/Canadian Phase II trial called PETROC has just closed which was addressing whether IP was more/as effective as standard IV therapy. Additionally, the trial was assessing the safety profile and practicality of IP therapy. This data is not yet available so we do not yet recommend it as an option to consider. All the evidence for intra-peritoneal chemotherapy has come from women having their first line treatment (ie at the time of diagnosis). There are no reliable data on use of intraperitoneal chemotherapy in women whose disease has relapsed, so this is not something that we could recommend in this case.
As for magnesium, we know that carboplatin chemotherapy can make the kidneys slightly leaky, so that women lose magnesium in the urine. Low magnesium levels can make people feel weak and tired, and can also cause low levels of other salts such as calcium. However, there is no evidence that low magnesium has any effect on how well chemotherapy works. The magnesium tablets won’t interfere with the chemo either positively or negatively.