This medicine may be harmful if swallowed. If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: breathing problems, muscle weakness/paralysis, shaking, increased sweating/saliva/tears, increased urine, nausea, vomiting, diarrhea, anxiety, headache, confusion, dizziness, drowsiness, slow or fast heartbeat.