⅓ to ½ml per nostril is ideal, but can deliver up to 1ml per nostril (expect some fluid to run off). If you need more than 2ml total, consider titration with second dose in 5 minutes
Consider administering an oral pain medication at the same time as the nasal medication or after about 15 minutes. As the effect of the nasal drug wanes, the oral medication takes effect
The single biggest reason for failure of<unk>  opioids is inappropriate dosing (usually underdosing)
Medications get absorbed in the nasal mucosa so inhalation is not needed and my cause deposit in the nasal pharynx
Intranasal sedation
Advanced airway adjuncts
Magic mouthwash
Nasal intubation
Mechanical ventilation 
Procedural sedation 
Procedural sedation
Bag valve mask ventilation