What does a higher doses of barbiturates result in?

Symptoms of an overdose typically include; sluggishness, incoordination, difficulty in thinking, slowness of speech, faulty judgment, drowsiness or coma, shallow breathing, staggering and in severe cases coma and death.

Barbiturates in overdose with other CNS depressants for example, alcohol, opiates or benzodiazepines is even more dangerous due to additive CNS and respiratory depressant effects