Peripheral Nervous System Drugs Quiz

Drugs Acting on the Peripheral Nervous System

Peripheral nervous system (PNS) refers to the network of nerves outside the brain and spinal cord. Several types of drugs act on the PNS, targeting various aspects of its function, including local anesthetics, autonomic ganglionic blocking agents, neuromuscular blocking agents, and anti-inflammatory agents.

Local Anesthetics

Local anesthetics are medications that numb specific areas of the body before surgery or procedures to prevent localized pain. They work by blocking sodium ion channels along axon membranes, preventing the propagation of action potentials along the axons. Two classes of local anesthetics exist based on their structure: ester-type (e.g., procaine and tetracaine) and amide-type (e.g., lidocaine and bupivacaine). In proper dosages, local anesthetics are considered safe and effective, but overuse or misapplication can lead to toxic side effects like convulsions, cardiac arrhythmias, or even death.

Autonomic Ganglionic Blocking Agents

Autonomic ganglionic blocking agents, such as curare and tubocurarine, are used to produce muscle relaxation and reduce the risk of complications during surgical procedures. They work by blocking the transmission of cholinergic signals at the postganglionic neuromuscular junctions, leading to muscle relaxation. However, their overuse can result in severe side effects, like weakness, paralysis, and organ system failure.

Neuromuscular Blocking Agents

Neuromuscular blocking agents (NMBA) are medications that cause a reversible and temporary blockade of the neuromuscular junction, paralyzing skeletal muscles without affecting the central nervous system. They are used in surgery and intensive care units to facilitate mechanical ventilation, manage muscle spasticity, and prevent muscle pain. Common NMBAs include pancuronium, vecuronium, and rocuronium.

Anti-inflammatory Agents

Drugs such as ibuprofen, naproxen, and aspirin act on the PNS by inhibiting cyclooxygenase (COX), an enzyme involved in the formation of prostaglandins. These substances contribute to inflammation and pain, and their suppression can help alleviate these conditions.

Drug-Induced Peripheral Neuropathy

Although most drugs affect the PNS by targeting neuronal or glial cells, some medications indirectly damage nerves through toxic metabolites or by altering the metabolism of other cells. Examples of drugs implicated in drug-induced peripheral neuropathy (DIPN) include chemotherapeutic agents, antimicrobials, cardiovascular drugs, psychotropic drugs, and anticonvulsants. DIPN can manifest as sensory deficits, motor weakness, or paresthesia in a glove and stocking distribution. The symptoms often develop weeks to months after drug initiation or dose increases, and the degree of toxicity varies depending on the drug involved.