Tom McNicholas has written widely on many aspects of urinary disease. He is particularly in demand for teaching on benign prostatic disease and urinary symptoms. He has major interests in the management of prostate cancer, the treatment of urinary stone disease and in making common urological investigations (especially prostatic biopsy) both painless and safer.
He has written over 150 major scientific papers which can be reviewed in the bibliography. Most recently he has been lead author of the chapter on Benign Prostatic Disease in the latest addition of Campbell’s Urology. This 4 volume textbook is the “bible” for urology and is used by urological experts worldwide. He is one of only a small handful of British urologists to have been recognised in this way.

GPs changing you from dutasteride to finasteride! Why? 11 Sept 2013

Many men and their partners are currently asking me why their GP has changed their (often very successful) drug therapy from dutasteride (Avodart) to finasteride (previously known as Proscar but now off patent and so now much cheaper.)

I do appreciate the pressure all GPs are under to cut prescribing costs. Everyone has to pay for the errors by the financial sector. However, I think that the rush to swap men from finasteride to dutasteride is being done on a purely price based analysis which has not taken into account several important features.  I would like to outline my views about the situation.

Firstly both are very effective and safe drugs. Large scientific studies done in thousands of men show that these are safe.
We have many years of experience with both, but especially finasteride. There has been more scientific study of dutasteride in recent years so more evidence is available for it, especially when used in addition to tamsulosin for men with big prostates, raised PSA levels and urinary symptoms (where the finasteride evidence is less).

Both will shrink the prostate by about one third over 6 months treatment in men who respond to these drugs.  Not all men do and some do respond but develop side effects that they can often live with. If you develop breast swelling then you should tell your doctor and examination and sometimes an ultrasound scan of the chest may be needed.

Both drugs reduce the risk of a man with an enlarged prostate needing surgery or developing painful urinary retention (being unable to “pee” and requiring emergency treatment) by about 50% compared to similar men not taking these drugs. My experience is that dutasteride kicks in more quickly which can be important.

Both drugs reduce the PSA level and seem to “switch off” the early cancerous and precancerous changes found in many men’s prostate cells. That may mean they can avoid ever needing biopies of the prostate for instance.  Unfortunately, if a man is going to develop more aggressive cells then these drugs won’t help and may even increase that risk very marginally. 

So if the PSA does not fall by 50% or if the PSA starts to increase your doctor should be asking  - Why?

So, who should get dutasteride?
I think that dutasteride should be preferred to finasteride where there is a distinct chance of a "significant" prostate cancer playing a part in the patient's urinary problems - as well as his BPH.  That is partly theoretical since dutasteride blocks the main 5 alpha reductase enzyme found in increased amount in the malignant prostate cell whereas finasteride does not.  Both work on the main 5ARI enzyme in the BENIGN prostate cell.  

There is a lot of interest in dutasteride for the management of men with prostate cancer and I will attach a recent paper from a major European study that I co-originated and co-led.  That shows a distinct benefit for dutasteride in delaying the progression of prostate cancer.

Obviously, it needs further work and further validation of this pilot study, but the science and the limited clinical experience would suggest that there is likely to be a role for dutasteride in such men.  I now try and point out to my GP colleagues when I am using dutasteride for this specific purpose. 

Secondly, there are a few other instances where dutasteride should be considered: 

1  Where the man does not tolerate finasteride for whatever reason and wants to continue with drug treatment then it is worth a trial of dutasteride.  Therefore dutasteride needs to be available on the local formulary from which GPs can prescribe. Often currently dutasteride has been removed from that list and is no longer available for GP prescription which I think is a mistake since it is unusual in medicine to only have one option from any class of drugs.  It’s a bit like playing golf with only 1 club!

On this basis alone I think dutasteride should be available though with limitations as set out here.  

2  When a patient has had only a moderately response to finasteride then a more powerful 5 ARI is indicated -  if they want to continue with drug treatment.

3  When there has been a response to finasteride but then the PSA starts increasing.  This can be a danger signal and requires explanation and therefore some investigation. But, in the meantime, it is reasonable to consider changing to the more powerful 5 ARI dutasteride.  

4 When rapid shrinkage of the prostate is needed eg to keep a man out of retention or out of hospital. Of course the man could be changed to finasteride later if necessary for financial reasons and if safe to do so.

Therefore, in summary:  
-where there appears to be a significant prostate cancer risk;
-when the man has not tolerated finasteride and wants to try the other 5 ARI;
-when there has been a response to finasteride  but not adequate and the man wants to try the other 5 ARI;
-when there has been a response to finasteride but then the PSA starts to increase and where the doctor wants to regain control before symptoms return.

Please note that in this situation the rise in PSA  needs to be investigated and explained as a rising PSA on finasteride or dutasteride suggests something else going on and especially the possibility of a more dangerous underlying prostate cancer.

I hope this helps.  It is a common question and I suspect many of these issues were not taken into account properly when the formulary decisions were made.  Let's face it, the formulary decisions were based largely on the cost of the 2 drugs and on a review of the solely BPH related evidence.  These drugs are more complicated than that!

I am not suggesting that everybody should be started on dutasteride, but there are clear indications, hopefully outlined above, where dutasteride should at least be available.  

I hope you agree.

With best wishes.

Tom McNicholas FRCS, FEBU
Consultant Urological Surgeon 
Private office (44) (0)1462-683814. 
Fax (44) (0)1462-683815  

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