Skip to main content
Drugs affecting the respiratory system
Drugs affecting the respiratory system
stimulants
They exert a reviving (analeptic) action due to the stimulation of vital centers in medulla oblongata (respiratory and vasomotor). The CNS stimulants of general action can intensify the transmission of nerve impulses or depress inhibitory processes. They have various tropicity to different structures of CNS. The centers of medulla oblongata are affected by: Nikethamide (Cordiamin), Bemegride, camphor. Cerebral cortex – caffeine; spinal cord – strychnine.
They stimulate the respiratory and vasomotor centers by decreasing excitability threshold of these centers, as a result their sensitivity to humoral and nerve irritants increases. This effects is especially potent when these centers are depressed, for instance, at intoxication with hypnotics of the narcotic type, ethyl alcohol and other drugs depressing CNS, in case of asphyxia of newborn etc.
Besides, the respiratory stimulants manifest functional antagonism to the substances of the narcotic type of action and can facilitate in recovering a patient from anesthesia in postoperative period.
Mostly, they are characterized be small margins of safety. Larger doses lead to the generalization of excitatory processes in CNS, increase of reflex excitability. In case of an overdose, one of the most dangerous complications is convulsions.
The drugs that mainly affect the brain (bemegride, camphor) induce clonic convulsions, while the substances affecting the spinal cord (strychnine) – tetanic convulsions. On that ground, respiratory stimulants are sometimes called convulsive poisons. In large doses the drugs, affecting the brain, can cause tonic-clonic convulsions.
By the mechanism of action, there are the drugs of direct action (bemegride, camphor) which stimulate the respiratory and vasomotor centers directly. The drugs of reflex action: Cytitonum (0.15% solution of cytisine) and lobeline stimulate H-cholinoreceptors of carotid sinus zone, from which the impulses stimulate the respiratory and vasomotor centers along the afferent tracts. These drugs are not effective in case of depression of the reflex excitability of the respiratory center by general anesthetics, narcotic hypnotics (for example, barbiturates). Mixed action (direct and reflex) is exerted by nikethamide.
