From the National Libray of Medicine:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6314932/

"Pentobarbital (PB) is a euthanasia drug in doses of 2 to 10 grams, causing death within 15–30 minutes. We report a case of recovery from lethal pentobarbital deliberate self-poisoning with confirmatory serum drug concentrations."

"Pentobarbital (Nembutal) is a short-acting barbiturate sedative-hypnotic that is widely used in veterinary practice for anaesthesia and euthanasia. It is also recommended as a drug for euthanasia or assisted suicide due to its rapid onset of coma and perception of a peaceful death. These popular media reports of pentobarbital being a peaceful method of suicide have led to increased interest in obtaining it from jurisdictions where it is less regulated [1]. It is unlikely that any resuscitative measures will be undertaken in these circumstances"