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What's the max dose for SL NTG?


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I've been curious on this for a while. I've read that the max dose is 0.4mg q 5 min x 3 doses max before but then I've read about higher dosages being used for pulmonary edema or hypertensive crisis. Does anyone know a max dosage for SL NTG and can point me to a reference that states it. Thank you in advance.

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There is no " max dose" of sl... Assuming hemodynamics stability, eg the theoretic max dose is when undesirable side effects such as hypotension or severe headache, you can give nitro and keep on giving it until you get tired of it. The common approach is ntg x3 then IV and tier to effect... The iv is simply to be able to give higher concentrations of the drug than in possible sublingually...

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Thank you for the response. This is kind of what I thought was going on but I couldn't understand why some references made it sound like there was an arbitrary maximum of 3 rounds of it and some of the others didn't mention it. The reason I was wondering is because in the situation that there was going to be a delay in getting IV vasodilators that with the short half-life of the SL NTG if you gave 3 doses 5 minutes apart and then stopped the patient could stop getting relief whereas if you continued giving the doses q 5-10 minutes until they received the IV vasodilators(assuming they remained hemodynamically stable) that they would continue to get some relief as opposed to none in the mean time. My question was kind of mainly geared towards a person with acute pulmonary edema and severe hypertension. Thanks again.

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Agreed with rcdavis; there is no maximum dose as long as the patient is hemodynamically able to tolerate more NTG. As a paramedic I've given 14-15 SL Nitro's to a patient on a single call and he continued to maintain a good blood pressure (severe CHF, rural setting with long transport and no IV nitro).

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  • 2 weeks later...

Think of it compared to a nitro IV drip: the bioavailability of SL nitro is ~75%. So, 0.4mg of nitro (or 400 mcg) provides about 0.3mg (300mcg) actual dose. IV route provides full bioavailability, therefore, the standard SL dose of 300mcg/5min would approximate an IV dose of 60mcg/min, since 300mcg/5min=60mcg/min. A 60 mcg/min nitro IV drip is pretty low dose. Of course, as already mentioned, dose limitations are ultimately dictated by hemodynamic (in)stability.

 

Another salient point would be: if you start a nitro drip and run it < 60mcg/min, then the pt is receiving less than a standard SL dose of 0.4 mg.

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also remember to consider ntg paste for those who initially respond to sl ntg if no IV ntg immediately available. I frequently use ntg sl x 3 then 1-2" of paste until IV ntg available(or if they get complete relief from 1-2 ntg sl then I apply the paste without the 2nd or 3rd ntg sl).

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