In a series of experiments the comparative actions of carbamylcholine,
physostigmine and neostigmine were compared in different species.
Carbamylcholine was shown to have the following undesirable effects:
(i) Respiratory distress due to bronchial secretion and constriction.
(ii) Marked drop in blood pressure due to vasocollapse.
(iii) Production of uncoordinated contractions of the rumen and inhibition
of the reticulum.
(iv) Profuse salivation. .
(v) Little effect on the large intestine of the horse or sheep.
It was more active on the stomach and bladder than the other two drugs
Physostigmine and neostigmine had very similar actions characterised by: (i) A slight rise in blood pressure after therapeutic doses. Evidence is
produced indicating that this may be due to adrenaline secretion.
(ii) Very little effect on the heart rate, salivary secretion or bronchioles.
(iii) Little effect on the stomach of the dog or donkey. Increased strength
of the contractions of the rumen and reticulum. Marked stimulation
of the large intestine in all species.
The impression was gained that neostigmine produced purgation in equines
and dogs with less signs of colic than did physostigmine.