Thread by @HillPharmD

#NARCAN Nasal Spray would be vastly more affordable/accessible if we acknowledged that 1 dose per kit is sufficient. Comparing plasma #naloxone concentrations following administration of various doses by intranasal (IN) & intramuscular (IM) routes tells us a lot. THREAD

Consider this graph from #NARCAN prescribing info (ignore top 2 lines). 0.4mg IM (vial+syringe) achieves lowest peak level...but it still works & has saved countless lives. 2mg IN (prefilled+MAD) achieves higher peak, & 4mg IN (NARCAN) achieves highest peak.

Follow concentration x6 hours...level of #naloxone in circulation 3 hours after receiving #NARCAN 4mg IN is higher than peak level after 0.4mg IM. Based on this data, it is reasonable to assert that NARCAN is effective for much longer than 30-90 minutes.

High peak dispels theoretical concern for insufficient effect & extended duration supports argument it may be ideal for populations unlikely to call 911. Same case can be made for #EVZIO 2mg IM (top line) which achieves highest peak w/longest predicted duration.

Some leading harm reduction experts (e.g. Eliza Wheeler @DOPEproject) argue against use of these high-dose #naloxone formulations due to substantially greater risk of inducing severe & protracted withdrawal symptoms. That is clearly a valid concern that requires further research.

*NOTE* I don't know if the 0.4mg IM dose in NARCAN PI is vial+syringe or auto-injector, but it shouldn't matter. The 2mg IN dose came from concentrated spray which is not the same as prefilled+MAD. Due to volume & drainage issues, prefilled+MAD might result in lower plasma level.