The most frequent reactions to metaxalone include:
CNS: drowsiness, dizziness, headache, and nervousness or "irritability";
Digestive: nausea, vomiting, gastrointestinal upset.
Other adverse reactions are:
Immune System: anaphylaxis, hypersensitivity reaction, rash with or without pruritus;
Hematologic: leukopenia; hemolytic anemia;
CNS: cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of serotonergic drugs with SKELAXIN used within the recommended dosage range and with SKELAXIN as a single agent taken at doses higher than the recommended dose (see WARNINGS, PRECAUTIONS: Drug Interactions, and OVERDOSAGE).