To all nitro users or former nitro users:  how much of the nitro ointment did you apply?  Did you feel any irritation from the medication?
My CRS doesn't usually work with these medication so I did not get any advice on how much to use.  I had read in one of these threads that someone used a pea sized amount.  I started with half of a pea sized amount and worked my way up to a pea sized amount but I get a lot of internal irritation if I use the pea sized amount.  So I am back to using the smaller amount.  It does seem to help.  Then I read one of the research studies and the patients there used 2.5 cms of ointment.  I appreciate any insight!

Hi darkeyes, 
My experience was use a pea sized amount 3 times a day & you have to get it on the fissure. Another CRS told me only to apply on outside never go in as you aggravate fissure. My fissure was sort of on outside going inside so applying on outside was easier for me. I just got headaches for few days.
I hope this helps 😊

Darkeyes, just a bit on the area, two times a day for me, I used to get a Q-tip and gently push some inside.
When it comes to irritation, I felt irritation when I was using it, to the point that I developed itching and rash and because I want it the fissure to heal so bad I end up with blisters.
Have to stop using it, so I started using Carlson vitamin E suppositories and baby desitin, Plus lots of Vaseline before a BM. 
Now that I am healed naturally I still use the baby desitin, when the area feels funny.:D

I use 0.2% nitro in vasoline (2% nitro diluted 10 to 1 with vasoline since that's what my pharmacy carries). I goop up a finger tip each night and insert. Not my idea of a good time but seems to work.
Surgeon brother tells me it will work even if not well inserted.
Nitro does give me mild headaches but I don't seem to notice if used right before sleep.
If the anal area gets irritated, which is seldom, I skip the nitro for a few days and just use vasoline.
The good part for me is that I am largely pain free after 6 months of this.

I use Rectiv (which is nitro). I was applying one inch worth of cream as the box/directions instructed, but I think I'll move down to half an inch since I'm getting itching that can be pretty uncomfortable at times.
I try to get the majority of it inside via my pinky finger, but I don't know how successful I am. I'm curious why some people say you have to get it on the fissure itself. I thought the cream was to relax the muscles down there, not to technically heal the fissure DIRECTLY, know what I mean? I doubt I'm getting the cream onto my fissure...

I use Diltiazem, which is similar to Nitro. I apply a pea-sized amount inside using my pinky finger (covered with a finger cot). I insert it to the first knuckle of my pinky. That works just fine for me and is what others have told me to do. I do get a little irritation (burning) sometimes when I apply it, but it goes away after a few minutes.
I really don't think you need to apply the cream directly to the fissure. My CRS said to just apply it a little inside, not right on the fissure. As long as you get it in there somewhat, it will do its job, which is to relax the internal sphincter muscle and increase blood flow to the area to promote healing.

Pea-size is actually the right amount.  Applying more can really knock you out (at least in my case). Never had any irritation, except headaches.  Couldn't handle it coz apart from headaches, I started throwing up too.  So switched to Diltiazem.

Crimeofpassion, 
The reason they say to get cream on the fissure is to get the blood flowing to promote healing . 
Anal Fissures: Nitroglycerin
Application of a 0.2% nitroglycerin ointment may help heal a long-term (chronic) tear, or fissure, in the anus. You rub a pea-sized dot of cream on the fissure twice a day. It is a good idea to either wear gloves when applying the nitroglycerin cream or wash your hands right after. The skin on your fingers can absorb the medicine and increase your chance of side effects.
An increase in muscle tension, also called resting pressure, in the internal anal sphincter can lead to fissures. Spasms and reduced blood flow to the anus may occur along with the rise in pressure, causing fissures or keeping existing fissures from healing.
Nitroglycerin is usually the first medicine used to treat a chronic anal fissure.
Headaches are the main side effect of nitroglycerin ointment. The risk of headaches and lightheadedness fromlow blood pressure is especially high if you use too much ointment at one time.
Some people also may experience itching or burning in the anal area. In some cases, people may develop tolerance to nitroglycerin, meaning that after a while the ointment no longer works to reduce muscle tension.
People using nitroglycerin ointment have increased chances of having lowblood pressure.

I just wanted to say thanks for all the replies. My parents were in town for over a month and I found it hard to post on this forum at the time. I ended up only being able to use half a pea size of nitro. I had to switch back to nifedipine after 15 days because nitro stopped working/my body got used to it. Since then I have switched back and forth between the two. The nitro still helped even though it was a small amount. I really appreciate all the advice!