Dear Friend, I cannot advice you on the dosage of Ativan. But I can suggest a way to reduce your fear. All phobia or mania are habitual mental perceptions. They exist without a base in reality. The permanent cure is in knowing deep down that small spaces are fine. Because of some past experience, your subconscious mind has decided that small space is dangerous. If someone would be buried alive, probably he will feel what you feel. But if the person survives the burial, still he will retain the fear to some extent. Ayurveda called a deeply engrained mental perception a sansakara, something which is so close that it appears a part of ourselves. Most of us are automatons, being worked by self made fears and mania. Claustrophobia is your self protection instinct. So curing it will look like dismentaling the alert system during wartime. You mind will not let you get cured. You have to ensure you mind that small spaces are ok. Meditation is a way to reach out to your mind and talk to it. Why to live in fear when life can be more beautiful without it ? Please find a good meditation trainer. Let s meditate app is very useful in absence of teacher. Best wishes!