If you took clonazepam *DO NOT* take nembutal!
Even if u have a tolerence to clonazepam nebmutal is a barbiturate not a benzo like clonazepam, it works very different! Also be weary that alcohol too can have fatal consequences mixed with nembutal, just as benzos and barbiturate. Also if you take barbiturates theres no need for benzos as they blow them out the water. I have enough experience to give you the some adivce, skip your clonazepam dose and take nembutal instead. As far as I know and in my experiences with amobarbital, butabital, phenobarbital and benzobarbital (the amobarb being the best, with pheno the worst) I have found that besides butabital the doses for barbitures are all very much equivalent, example 100mg amobarbital is supoosed to be eqivalent to 100mg secobarbital or 100mg nembutal, however a quick search for 'nembutal oral dose' shouldn't hurt at all and I would def. recommend it, its been 1yrs since I had any amobarbital, precisley.
Also thing about amobarbital, sure it goes for nembutal as well, it is to be taken orally on an empty stomach or 2hrs after your last meal, for maximum absorption.
p.s. 1 single beer on top of 100mg amobarbital had me feeling like I drank 4-5 and on 200mg phenobarbital and 3-4 500ml (tall boys) I woke up after20+hrs.