Hello Luke
First of all I have to congratulate you for such an amazing achievement. If you gave a 2mg dose of Diazepam to someone that has never had it, they would certainly feel the effect within twenty minutes. 5mg or a 10mg tablet for sure would maybe even put them to sleep.
Most people know from the Patient Information Leaflets, that Diazepam and similar drugs were always intended for short term use, but the truth is, we have drifted into a situation where the drug has been put on repeat prescription and before you know it, months or years have passed, which is true in your case.
To reduce your intake from 130mg a day to just 8mg is an amazing personal achievement and I salute you for it. You should allow yourself to feel proud of this huge step to complete withdrawal.
As you know, the active ingredient in 'Atarax' tablets is fundamentally an Antihistamine. You can purchase the same active ingredient off the shelf in any supermarket, but the amount of Hydroxyzine Hydrochloride is much less. The strength of Atarax is only available on Prescription.
The major side-effect of most antihistamines is drowsiness. You will notice that in the shops, well known brands promote so-called "Non-Drowsy" formulas, with added ingredients to counteract the soporific effect. For this reason, they are sometimes prescribed to people suffering with anxiety, not for what the drug is principally designed for, but precisely because of the side-effect. Your GP is right in saying it will "take the edge off", as the drowsiness can feel similar to the effect of Diazepam.
The difference is, (and this is the good thing), that where stopping Benzodiazepines suddenly can put you through hellish withdrawal, you can stop taking Atarax at any time, and because it is not addictive, you won't experience any cravings.
The answer to your question is Yes! Your body will/should adapt so that the drowsiness becomes less. Every patient is different so will be told to try dosage in different ways. I was advised to take two to three tablets in a single dose just before bedtime, but to use my own judgement, and try to go three nights on, two nights off, and so on, to prevent getting too used to them that they became ineffective.
This has worked for me, so my need for Diazepam to sleep has been eliminated. It shows how different we all are, because I remember taking my first dose and frankly not feeling much at all. If one tablet is affecting you so severely that you can't function during the day, perhaps you could speak to your GP by phone, explain how you are affected, and see if he/she suggests shifting your dose to the evening.
The most important thing to remember is just how successful you have been. To be coping more on Atarax and less on Diazepam is a huge improvement for you, and when the time comes, you may feel ready to do without the Atarax as well. Your body won't react anywhere near as severely as benzodiazepine withdrawal, so you are definitely on course and I think your GP is giving you good advice.
Another alternative Luke would be to ask for a prescription of a lower dose tablet than the 25mg you are on, and see if you cope better with a smaller dose during the day and then use your 25mg at night?
I hope that my comments have helped, and being in a very similar situation, means I really can empathise with you.
Best wishes to you, keep hold of your determination, and praise yourself internally for a pretty amazing journey off such a high dose of the addictive stuff.
Take care Buddy.