Greater following oral than intranasal administration. Analgesics are administered orally and anesthetics by intravenous injection. Analgesics primarily act directly at synapses in the spinal cord, whereas anesthetics act in the brain. Anesthetics are more selective for inhibition of A d and C fibers than are analgesics. Analgesics are more selective for inhibition of the sensation of pain, relative to other sensory modalities.
Analgesics have a lower therapeutic index than anesthetics.
Membrane proteins activated by endogenous peptides. Enzymes which convert arachidonic acid to prostaglandins. Proteins which are present in the brain but not the spinal cord. Peptic ulcer and bleeding. Symptoms on withdrawal because of physical dependence.