Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
confusion, agitation, hallucinations;
weak or shallow breathing;
slow heart rate, weak pulse; or
a light-headed feeling, like you might pass out.
Side effects such as confusion, depression, or excitement may be more likely in older adults and those who are ill or debilitated.
Common side effects may include:
loss of balance or coordination;
nausea, vomiting, constipation;
sleep problems (insomnia), nightmares; or
feeling restless or excited (especially in children or older adults).