Hi,you can take verapamil
your usual dose along with lorazepam
.just space the timing with both the drugs,take lorazepam few hours after you have taken verapamil.Also if its a long haul flight make sure you don't remain static in your seat,walk down the aisle of aircraft every hourly or so to prevent blood stasis
in your limbs
.Take care and happy journey and wishing your son a speedy recovery and good health.