...The Cialis literally left me hanging a couple of times. It gave me severe headaches. The next day I got the back ache. It caused the stopped up nasal passages. The Cialis dose was the 20mg pill taken one hour before the session. Ibuprofen and nasal spray helped but the random ineffectiveness caused me to ask my doctor about a change.  

 
The switch to Viagra (100 mg) always works. The headaches aren't as bad, I don't get the backache, and the stuffiness isn't as bad either. I do get the sensitivity to bright light and sometimes indigestion. I've cut back to 50 mg now and I take it about 5 minutes before the session. It works.

 
This month my doctor gave me a prescription for the 20 mg  Sildenafil  generic for Revatio. I get thirty a month for $23.00 and some few cents at my local pharmacy. I take three (60 mg) it works just like the Viagra (which is also Sildenafil).

 
I know this isn't what you asked but I thought I'd post it as it's related and the more information the better.
This is just my experience. Everyone is different and none of what I said could apply to you. Do talk to your doctor before doing anything.

-- Modified on 6/13/2017 7:46:01 PM

Thanks. I was interested in Cialis because of it s greater compatibility with food and drink. Your experience is something to consider. I have had very few side effects with V.

I have used both, not at the same time.  Cialis gives me severe reactions,severe headache, severe backache, bad indigestion, stuffed up nose. And didn't work all that well.  
Viagra works like a charm.

... my experience differs from what others are posting.  

I used sildenafil first.  Took it just before sessions or up to 2 hours before.  Effective, no headaches or blue vision, but I get very red-faced and can't "cum" (no ejaculation; dry shots).  Girls notice, and comment.  

Switched to tadalafil.  Take it around 24 hours before session.  Effective, no headaches or blue vision, no flush, and I can cum almost normally.  Erections are still strong for another day.  

So I prefer C.

back in 2009 I got  high blood pressure and the doc put me on medication. The side effects were terrible I ended up with total ed for 12 days either no feeling or felt like ice in the groin area. the doc gave me all three to experiment with levitra, viagra and cialis. All three worked but side effects from HP was too much so he cut the dosage in half and I was back to normal. So now I take ed drugs for insurance even though evertything works. The problem once you had ed you think about it everytime the fun begins and worry if you can perform. Imho opinion cialis is by far the best. The only side effect I had was with viagra. I went to a strip joint not expecting anything and wanted to experiment with 50mg to my surprise a gal wanted see after hours at 3pm and I wasnt sure it would still work so I pop another 50. She came at 4am and everything work fine but had a bad headache later.The cialis I have now is from the shutdown pharmacy in india, it still works beyond the  expiration date and have erections like I was 18 up to 5 days. I dont know if that due to the india stuff being better or since in reality I dont have a problem only worry or nerves. right now  the only issure is finding a new pharmacey so pm me if you know of some.