Bloxiverz is used to reverse the actions of nondepolarizing neuromuscular blockade following surgery o Positively charged, cannot cross the blood-brain-barrier, minimal effects on the brain and fetus o Mechanism of Action: Act as substrates for cholinesterase Cholinesterase splits neostigmine more slowly than it splits acetylcholine. Hence, once neostigmine becomes bound to cholinesterase, the drug remains in place for a relatively long time.B/c cholinesterase remains bound until it finally succeeds in degrading neostigmine, less cholinesterase is available to catalyze the breakdown of acetylcholine. Therefore, there is more acetylcholine available to activate cholinergic receptors. o Pharmacologic effects: When used therapeutically cholinesterase inhibitors usually affect only muscarinic receptors on organs and nicotinic receptors of the neuromuscular junction (NMJ) Muscarinic Responses: Identical to those of direct-acting muscarinic agonists
Cause bradycardia, bronchial constriction, urinary urgency, increased glandular secretions, increased tone and motility of GI smooth muscle, miosis, and focusing of the lens for near vision Neuromuscular Effects: Are dose-dependent At therapeutic doses, these drugs increase force of contraction At toxic doses, these drugs reduce the force of contraction Central Nervous System Varied effects Therapeutic levels can produce mild stimulation, whereas toxic levels depress the CNS, including the areas that regulate respiration For CNS effects to occur, the inhibitor must first penetrate the blood-brain barrier, which some cholinesterase inhibitors can only do in very high concentrations o Administration and Dosage: May be administered IM, IV, or by subQ Poorly absorbed following oral administration so this route has been discontinued in the US Duration of action is 2-4 hrs Available as 2 salts: neostigmine bromide (PO) in 15 mg tablets and neostigmine methylsulfate (IM, IV, and subQ) in solution 0.5-1 mg/mL Dosage is individualized but ranges from 15-375 mg/day administered PO in divided doses o Therapeutic uses: Myasthenia Gravis This is a major indication for neostigmine and some other reversible cholinesterase inhibitors Reversal of Competitive (Nondepolarizing ) Neuromuscular Blockade Cholinesterase inhibitors can reverse the effects of competitive neuromuscular blocking agents 2 clinical applications: 1. Reversal of neuromuscular blockade in post-op patients 2. Treatment of overdose with a competitive neuromuscular blocker Nursing intervention: artificial respiration must be maintained until muscle function has fully recovered. At doses employed to reverse neuromuscular blockade, neostigmine is likely to elicit substantial muscarinic responses. These can be reduced with atropine o Complications: Excessive Muscarinic Stimulation
Accumulation of acetylcholine at muscarinic receptors can result in excessive salivation, increased gastric acid secretions, increased
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- Spring '14
- Selective serotonin reuptake inhibitor, Antipsychotic, SGAs