Prazosin - Trial of One (Me) - Advanced Prostate...

Advanced Prostate Cancer

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Prazosin - Trial of One (Me)

Scout4answers profile image

To my surprise my urologist readily prescribed Prazosin to replace Tamsulosin, after reading the retrospective study that Bruce SF supplied me with and I forwarded to my Doc with my request to change drugs.

As a trader I always look at risk and reward, this one seems to be a no-brainer, very little risk and plenty of potential upside, unless I have a reaction to the drug itself.

Purple Bike wrote an excellent post that summarizes my thinking. I hope that in 10 years I can report that My PSA and scans show no progression.

Thanks Bruce SF for the idea. set my mind racing as well. ;-)


4 days ago

I would suggest that the retrospective study, showing benefits for prazosin user patients, has a better chance than the average retrospective study of the drug in question to actually be beneficial.

Users of prazosin have a worse cancer status than controls, otherwise they have no apparent dissimilarities..Selection bias could clearly play a role as is so often the case with retrospective studies. Users of P might have more healthy behavior, better health insurance and so on than the PCa patients not on BP medication. But the users of the second BP medication, tamsulosin, did in most respects not have an improved outcome compared to controls, and had a greatly inferior outcome compared to prazosin. Why is this? Of couse there can be confounders, but at the least, it is not obvious that users of tamsulosin have worse health behavior etc than users of prazosin. P and T are similar drugs, both being α1-adrenoceptor antagonists

Then there are the preclinical studies, maybe of limited use on their own, but buttressing what clinical data there is. From the study referenced by Scout4answers: “There is substantial evidence that the quinazoline α1 antagonists (terazosin, prazosin and doxazosin) display cytotoxicity in prostate cancer cell lines, effects that are not observed with the sulphonamide derivative tamsulosin. ........ In vivo studies in mice have shown that these effects also occur at clinically relevant doses, with reduction in tumour growth, metastasis and decreased angiogenesis observed in models of prostate cancer”

So lab and animal studies show protective effects from prazosin but not from tamsulosin. The retrospective study on men likewise showed a greatly superior effect of P compared to T and controls.

This is of course very far from any proof of efficacy of P for PCa, which will need a RCT phase 3 years ahead in the future if there ever is one. But the combination of lab/animal data and retrospective study pointing in the same direction to me indicates that it could be worthwhile considering prazosin, if side effects are tolerable and in particular if one has an interest in lowering blood pressure. This post set my mind racing.

Swing dancing with Coco at pier 290 in Lake Geneva last weekend to celebrate # 74.

10 more years of this would be a fine outcome.

41 Replies

N=2. I need to take a BP med and am going to try:BP Prazosin (start 1 mg 3x/day, inc to 5 mg 3x/day)

My continuing research found this post by Patrick --- 4 YEARS AGO!You are light years ahead of your time Patrick.

Prazosin with Docetaxel?

pjoshea13 profile image


4 years ago•6 Replies

New Australian cell study below [1].

Looks like Prazosin may increase Docetaxel-induced toxicity.

"Some quinazoline-based alpha1-adrenoceptor (ADR) antagonists have previously been shown to have cytotoxic actions in PCa cells, but there is no research into their effects on docetaxel-induced toxicity."

"We hypothesised that prazosin, but not tamsulosin, in combination with docetaxel would possess synergistic cytotoxic actions on PC-3 and LNCaP PCa cells."

Both drugs have been used in the context of BPH:

Prazosin [2]:

"Prazosin is ... useful in treating urinary hesitancy associated with prostatic hyperplasia, blocking alpha-1 receptors, which control constriction of both the prostate and urethra."

Tamsulosin (Flomax) [3]:

"Tamsulosin, and other medications in the class called alpha blockers, work by relaxing bladder neck muscles and muscle fibers in the prostate itself and make it easier to urinate."

From the new paper:

"Prazosin sensitised both cell lines (PC-3 and LNCaP) to docetaxel-induced toxicity. This effect appears to be mediated by autophagy and may also involve apoptosis. These sensitising effects of prazosin appear to be largely independent of ROS production. In contrast, tamsulosin did not affect docetaxel-induced toxicity."





Prazocin is alfa receptor blocker ,relaxes smooth muscle in bladder...thus facilitating urine flow. Similar to prazosin is Doxazosin...these two drugs have anti cancer qualities. Either one can be used to lower Blood Pressure and slow PCa growth at the same time.

Thanks, looks like doxazosin would be more convenient as you take it once a day.

Yes I take Doxazosin 4 mg at bedtime. Wake up 2 or 3 times at night.(in 8 hours)

cesces profile image
cesces in reply to Scout4answers

prazosin vs Doxazosin vs flomax

Which has the strongest evidence of being effective against prostate cancer

By the way, I agree with you... all these decisions need to be made on a risk reward basis. And this seems quite contrary to the training and philosophy of modern medicine.

Scout4answers profile image
Scout4answers in reply to cesces

prazosin and Doxazosin

Isn't prazosin a safer bet, since this is the drug in the retrospective study?

Dumb questions

1. Prazosin is basically used for hypertension and ease of urination?

2. Prazosin also helps improve the effectiveness of Docetaxel treatment.

Do I have that right?

Does Prazosin suppress prostate cancer on its own?

LearnAll profile image
LearnAll in reply to cesces

There are preliminary research on anti PCa cancer effect mainly in petri dishes. But, lot of PCa sufferers also have some degree of BPH and it is better to take Doxazosin than Tamsulosin.

Scout4answers profile image
Scout4answers in reply to cesces

Yes, to 1&2 but no trials to prove it’s effectiveness.

Just checked goodrx. Prazosin is pretty inexpensive.

Happy birthday Scott 🥳

Thanks Planing on at least 31 more but hedging bets just in case. Living life at 3x normal speed, fun quotient is off the charts.

3x normal is great. Happy for you Scott

Very fine information Scout I will a,so look into Prazocin as I an on other BP medications recently. Thank you.

I am happy to share some info that may possibly be of help to you Paul, as you have been so generous in sharing what you have learned with me and the rest of the group.

Yes, thank you Scout. Please send the links of the research you have on this, and any other insights. Either here or in PM. Paul 🙏

this is the retrospective study that Bruce SF shared that sent me down the rabbit hole. every thing else is in this thread.

will this be harmful if BP is lower side of normal?

Scout4answers profile image
Scout4answers in reply to spw1

I think that is a question for your Urologist or MO

spw1 profile image
spw1 in reply to Scout4answers

Yes thanks.

GeorgeGlass profile image
GeorgeGlass in reply to spw1

That’s why i probably couldn’t use it. Since i lost weight and take sone other supplements that lower bp, i think it would be too risky for me. My bp is around 100/60 resting.

spw1 profile image
spw1 in reply to GeorgeGlass

I think that we have to wait after the chemo to see how things are.

MateoBeach profile image
MateoBeach in reply to spw1

I seem to recall that when first starting it there can be a big drop in BP, risking syncope. So many start with 1/2 mg at bedtime for a few days, then can rapidly ti trate up without problem. Discuss with your doctor for sure.

Thanks great info

spw1 profile image
spw1 in reply to MateoBeach

thank you. For now will not add it as my husband begins chemo on Friday

Good for you . I will take this up with my oncologist too. Thanks and Good luck

I am all set to go for prazosin (or doxazosin if this can be judged equal despite not being in the study posted by Scout4answers).

Nothing is perfect and I understand there is one drawback, for a case like mine with sudden strong urination urge bordering on incontinence (MInipress = prazosin)

That problem was for “stress incontinence”, which means leakage during sneezing or coughing or similar abrupt abdominal pressure increases stressing the bladder sphincter. Urge incontinence you describe is different, coming from spasmodic contraction of bladder muscle as it fills. A sudden urge precedes loss of control. Prazocin should not aggravate that type.(Third type is overflow incontinence when bladder overfilled from obstruction.)

Another great rabbit hole ! Thanks a bunch Scout. Lol.So I don’t have a need for prazosin except my mHSPCa, but in wanting to learn the mechanism of actions against PCa I came across this informative 2021 article on several repurposed drugs with excellent tables like Table 1. Repurposing non-oncology small-molecule drugs for cancer therapy.

Table 2. Repurposing non-oncology drugs under clinical trials.

And of course graphics (i love tables and graphs)

Scout4answers profile image
Scout4answers in reply to KocoPr

Nice find Koco, love your name,

The woman I love, is just the same.


I call her Coco, because she's sweet,

her love for me, is quite complete.


She is always loving and very caring,

When thinking of others, there's no comparing.

To Scout4answers (re: love vs love)

Ahhhh that was so cool....

better wear a bib you're starting to drool....

Good Luck, Good Health and Good Humor.

j-o-h-n Wednesday 06/15/2022 6:46 PM DST

LOL unfortunately drooling is a part of my life

All I know is when I took those drugs, they were nasty! Almost falling flat on my face multiple times when getting up from seated position due to dizziness! Was glad when I stopped needing it (post RP). But is interesting the re-purposing! I only worry about Big Pharma just trying to max profit life out of a drug and therefore providing questionable methods to findings.

It's all good, no matter! Thanks for posting!

CAMPSOUPS profile image
CAMPSOUPS in reply to Cooolone

I agree with the SE's from these meds ( Tamsulosin-Flomax ).

Another credit to our forum here was a member pointing out the SE's which remarkably I had not looked into.

A year after chemo I was still huffing and puffing and needing to rest after going up the stairs. I thought that was just the way it was to be until I experimented with stopping flomax ( at least a year ago ) and my pee frequency remained the same ( luckily ) and the heart pounding dizzying low blood pressure effects went away.

I had a white/green blob in my vision when I got up at night with Flomax - Tamsulosin, switched to RapidFlo - Silodosin and it went away.

Nice. Well not at first with Flomax lol. Glad Silodosin works for you.

I guess if you have high blood pressure, then Prazosin is a drug of choice because that is exactly what it is designed to do. Tamsulosin is to relax the prostate to help with urination. My PCa was Gleason 9. Brachytherapy effected my ability to urinate, so I was prescribed Tamsulosin night and morning - not much help there. So I now take Doubluts which is a combination of Tamsulosin and Dutasteride and that works for me. There have been studies done showing that Dutasteride has benefits in treating PCa, so I am happy to stay on Doubluts even though it does mask PSA. With ADT (Zolodex) and follow up treatment of 23 sessions of EBRT, my PSA is .008 (2 × 3 mth tests) so, so far so good. Recent pain in my chest bone under my left arm showed no mets - so I'm good - so far, lol. And I do not have high BP. Always think basics and reasons for what you are taking, remember the KISS principle. Good luck.

Scout4answers profile image
Scout4answers in reply to tad4

Doubluts interesting combo...Glad it is working for you.

PSA is .008 Awesome #, sounds like you are on a good path.

The recommended dose of prazosin for BPH is 2 mg 12h which I read as 4 mg per day. The recommended dose for blood pressure is 6 - 15 mg per day.

But the typical dose of prazosin for PCa patients in the Australian study was, surprisingly for me, only 1 - 2 mg per day.

As MateoBeach indicated, 0.5 mg is the way to start. Anyone with an idea of how high one should aim to increase to for capturing the potential anti-PCa effect?

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