Thank you so much... but we only got one for that day. so it says take one. but no instruction's how long it will take effect or how long before the test to take one.
If he does not normally take any kind of benzodiazepine (ie Ativan, Xanax, Valium, Klonopin), then it should be effective for him, although of course it's impossible to predict how each person will react to a medication. I personally feel that Xanax would be the most optimal choice as a pre-medication for a diagnostic test that is causing anxiety.
As for when he should take it, the instructions should be on the Rx bottle. If you're unsure, get clarification from the prescribing doctor. Hope it goes well for him!