💊أدويه الجهاز العصبي
#Pharmacology_of_CNS
#CNS
#Anesthetics
حا نتكلم الليلة عن👇
✔️NEUROMUSCULAR BLOCKERS
✔️LOCAL ANESTHETICS
دي حا نشوف فيها
✅Metabolism
✅Onset and duration of action
✅Actions
✅Allergic reactions
✅Administration to children and the elderly
✅Systemic local anesthetic toxicity
✔️NEUROMUSCULAR BLOCKERS
🔘Neuromuscular blockers are used to abolish reflexes to facilitate tracheal intubation and provide muscle relaxation as needed for surgery. Their mechanism of action is blockade of nicotinic acetylcholine receptors in the neuromuscular junction. These agents, which include cisatracurium, pancuronium, rocuronium, succinylcholine, and vecuronium
✔️LOCAL ANESTHETICS
🔘Local anesthetics block nerve conduction of sensory impulses and, in higher concentrations, motor impulses from the periphery to the CNS
🔘Na+ ion channels are blocked to prevent the transient increase in permeability of the nerve membrane to Na+ that is required for an action potential
🔘Structurally, local anesthetics all include a lipophilic group joined by an amide or ester linkage to a carbon chain, which, in turn, is joined to a hydrophilic group
🔘The most widely used local anesthetics are bupivacaine, lidocaine, mepivacaine, procaine, ropivacaine, and tetracaine
✅Metabolism
🌀Biotransformation of amides occurs primarily in the liver. Prilocaine, a dental anesthetic, is also metabolized in the plasma and kidney, and one of its metabolites may lead to methemoglobinemia. Esters are biotransformed by plasma cholinesterase (pseudocholinesterase).
✅Onset and duration of action
🌀The onset and duration of action of local anesthetics are influenced by several factors including tissue pH, nerve morphology, concentration, pKa, and lipid solubility of the drug
اهم عاملين هم ال PH و الPKa
🌀At physiologic pH, these compounds are charged. The ionized form interacts with the protein receptor of the Na+ channel to inhibit its function and achieve local anesthesia
🌀Duration of action depends on the length of time the drug can stay near the nerve to block sodium channels
✅Actions
🌀Local anesthetics cause vasodilation, leading to rapid diffusion away from the site of action and shorter duration when these drugs are administered alone. By adding the vasoconstrictor epinephrine, the rate of local anesthetic absorption and diffusion is decreased
🌀Some local anesthetics have other therapeutic uses (for example,lidocaine is an IV antiarrhythmic).
✅Allergic reactions
🌀Patient reports of allergic reactions to local anesthetics are fairly common, but often times reported “allergies” are actually side effects from epinephrine added to the local anesthetic
🌀True allergy to an amide local anesthetic is exceedingly rare, whereas the ester procaine is somewhat more allergenic
🌀Allergy to one ester rules out use of another ester, In contrast, allergy to one amide does not rule out the use of another amide.
✅Administration to children and the elderly
🌀Before administering local anesthetic to a child, the maximum dose based on weight should be calculated to prevent accidental overdose
🌀Because some degree of cardiovascular compromise may be expected in elderly patients, reducing the dose of epinephrine may be prudent.
✅Systemic local anesthetic toxicity
🌀Toxic blood levels of the drug may be due to repeated injections or could result from a single inadvertent IV injection.
🌀Treatment for systemic local anesthetic toxicity includes airway management, support of breathing and circulation, seizure suppression and, if needed, cardiopulmonary resuscitation.
🅿️بكدا نكون خلصنا فصل ال Anesthetic
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