Jack wasn't expecting Glen to react like that - he'd expected it to be gradual, with the other man excusing himself to lie down, probably waking up with a fever and headache -

"Glen? Glen!" He yelled, immediately lunging to his side and cradling his shoulders. "Oh, god, Glen, what - "

He quickly patted himself down for the antidote, tearing the cork out with his teeth and tipping it into his mouth, before leaning in to transfer it by direct contact.