Hi Monica, LDN is one of those many drugs that affects people differently like VicChang has said. I was on it for many years and I changed the dose many times also.
Firstly it has to be compounded, so it would be best to ask for it to be compounded into 1.5mg capsules, and that way you can easily alter your dose as YOU - not your GP - requires - as and when. Open the 1.5mg capsule and spill the powder onto a sheet of paper - hard to see the powder on white paper so a coloured sheet is best. Then with a knife, divide the powder into 3 equal parts, and use one of those- put each of the remaining portions into small pill containers for the next time you want a small dose - ULDN - ultra low dose naltrexone it is called. It is pretty expensive, so try not to waste any.
Another tip, ask the compounding chemist to only use glycine as the filler when making up the compound Some will use a cheap filler which does more harm than good. Using glycine utilises the LDN to the best.
The GP can make the script out for 4.5mg capsules, but the compounding chemist can change that to 1.5mg capsules.
It is best started on 1.5 mg or even .5mg capsules, per day at night time, and very slowly increase by 1.5/.5 mg weekly until you are on the dose that suits you. Some people start on 4.5mg and wonder why it doesn't work very well. You may want to stay on .5 mg/day if that is the dose that suits you. Taking more does not necessarily mean that it will work better for you, and remember it will take a little time for good results to show. Strange as it may seem, .5mg is actually stronger than 4.5mg.
Mine started immediately - I bought .5 mg capsules online and the day they arrived by post, I opened the parcel in the kitchen, immediately took one capsule, and struggled to get to the bedroom a few metres away as I was going to sleep. Same result for the next however many years. Eventuallly stopped taking them as they didn't work for me anymore, which is a problem with LDN - you will have to change the dose as it needs this to keep working for some unfathomable reason.
All the best, and hope this advice is of some help to you.

Hives and itchy/closing throat is usually a allergic reaction.

It's listed on its drug page under rare but serious side effects. Like most medications also list.

Make sure to eat on it... or have something in your stomach. It rips mine up.

Hi Annie2PO, Sorry to hear that you had that result, but be assured, I am almost 100% sure that those symptoms could not have been caused or influenced by LDN as an entirely different pathway of action. If a steroid shot calmed it down, that makes me 150% sure it could not have been caused by LDN. OK, it may - just may - have been an allergic reaction to something, but hardly LDN. Something else that you ate, drank or came in contact with about the same time.
If it was the LDN capsule, it then could only be the filler they use with the product when compounding it. Some compounding chemists always take the cheap way, and that is to use cheap fillers that can cause troubles when taken by susceptible people. That is the only reasonable explanation, and once again, I am sorry it happened to you. Try again, and this time with a different compounding chemist and state that the filler must be glycine and explain you had a bad reaction to the filler in the last batch. If you have some of the last batch you could send one or two capsules to them to identify what filler was used, and to avoid that in future.
All the best.

LeslieS2 they don't make naltrexone at those low doses, so you have to find a compounding pharmacy that will grind those pills up, separate them into to the correct doses and repress or put them in capsules. Have to have a filler and or binder to do that. My PCP prescribes the low dose, it goes to that compounding pharmacy. Then I get pills/ capsules at the prescribed dose instead of the larger dose that is available for general prescribing.