“…The intranasal route of ketamine administration has several advantages. A large surface area, high permeability and extensive vascularisation of the nasal mucosa cause rapid absorption of the drug [30]. In a cross-over trial, ketamine was administered intranasally to 20 patients with breakthrough pain, randomly assigned to groups receiving 10-50 mg of ketamine (patient-controlled dose) or placebo -in 45% of patients treated with ketamine, pain intensity was reduced by 40% or more, compared to 5% in the placebo group (p = 0.0078) [31].…”