Pedi. recommended zyrtec, (cetirizine) 9 mo boy. i mistakenly gave him 5x the dose (3 ml vs 8 drops). no visible sideeffects. is it ok now to restart 8 drops?

Not right away: Wait for a couple of days before you resume the medicine in the corrected dose, or call the doctor and ask for advise,medicine like Zyrtec (cetirizine) accumulate and take a while to be cleared from the body. Bilsalamah inshallah

No: Not to be used under 2 yrs of age. That being said, some physicians will off-label prescribe it 6 mo - 2 yr olds at around 2.5 - 5 mg/day. If you gave 3 ml (= 3 mg) it is unlikely child would have any significant side effects. Again, in general, not advisable to give kiddos under 2 antihistamines.