Premeasure the correct dose, then use an infant medicine dropper to either slowly drop the medicine into your baby's mouth, let her suck on the dropper, or squirt it quickly back into the corner of her cheek. Note: If your baby is crying, the last approach may cause her to gag and spit the medicine out.
If your baby hates the dropper, let her suck the medicine through a clean bottle nipple.
She won't cooperate? Try mixing the medicine with a small amount of formula or breast milk.
Pop a pacifier in your baby's mouth immediately after giving her the medicine -- it will make her more likely to suck and swallow.
If your baby spits out what seems like all of the medicine, or vomits within five to ten minutes after you administered it, repeat the full dose. (If the medicine stayed down for about 20 minutes before she vomited, you don't need to give it to her again.)
Try giving infant acetaminophen in suppository form (a good option for a vomiting baby).