Is 10 800mg skelaxin (metaxalone) an overdose?

Definitely, yes. The recommended metaxalone dose for adults is one tablet (800 mg) 3-4 X/day. Maximum daily dose is 3200 mg. Many doctors prescribe 2 tab.(1600 mg ) BID.
10 pills in a day? Taking 10 pills of skelaxin (metaxalone) 800 mg is definitely an overdose. Therapeutic dosage is three times daily.