nitrous oxide: pharmacology + how it works

what is pharmacokinetics?

what the body does to the drug: uptake (absorption), distribution, metabolism, elimination

what is pharmacodynamics?

what the drug does to the body, including its effects on the nervous system and organs

what is the blood-gas partition coefficient?

measures how easily nitrous oxide moves from the blood into the brain

low coefficient= faster onset and recovery

nitrous oxide’s coefficient is 0.47, which is very low

why does nitrous oxide have such a rapid onset ?

bc it is poorly soluble in blood, allowing it to reach the brain quickly (3-5 mins)

does nitrous oxide undergo liver metabolism

no

about 99% is exhaled and unchanged through the lungs

only a tiny amount (0.004%) is metabolized in the GI tract

why is nitrous oxide ideal for outpatient dentistry

works quickly, easily adjusted, wears off quickly, doesn’t rely on liver metabolism, allows patients to recover rapidly

what does MAC (minimum alveolar concentration) measure?

the amount of inhaled anesthetic needed to prevent movement in 50% of patients during a painful surgical stimulus

what does a low MAC indicate?

a drug is more potent bc less drug is needed

is nitrous oxide a potent anesthetic?

no

its MAC is 104-105%, making it one of the least potent inhalation anesthetics

why can’t nitrous oxide alone reliably produce surgical anesthesia?

bc achieving its MAC would require more than 100% nitrous oxide, which is impossible while providing enough oxygen

how does nitrous oxide produce analgesia?

alters pain perception by stimulating the release of endorphins, activating descending pain-control pathways, and reducing how the brain interprets pain

doesn’t numb tissues like LA

does nitrous oxide eliminate pain completely?

no

it raises the patient’s pain threshold, making procedures feel more comfy, but LA is still needed for painful procedures

how does nitrous oxide reduce anxiety?

depresses CNS, producing relaxation, calmness, reduced fear, and a less emotional response to treatment

what body system is least affected by nitrous oxide?

the CVS

it produces very little change in BP, HR, and cardiac output

how does nitrous oxide affect respiration?

very little

patients continue breathing on their own, although respiration should still be monitored

why is oxygen always administered with nitrous oxide

to maintain a dequate oxygen levels and prevent hypoxia

at least 30% oxygen should always be delivered

what is diffusion hypoxia

when nitrous oxide leaves the bloodstream rapidly after treatment, it can dilute oxygen in the lungs, temporarily lowering oxygen levels

how is diffusion hypoxia prevented

administer 100% oxygen for about 3-5 minutes after discontinuing nitrous oxide

what symptoms can diffusion hypoxia cause

headache, dizziness, nausea, lightheadedness

why is nitrous oxide considered easily reversible

once admin stops, the gas rapidly leaves the lungs and bloodstreatm, allowing patients to recover within minutes

what is the max recommended concentration of nitrous oxide in dentistry

70% nitrous oxide with at least 30% oxygen