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Local Anesthetics

Definition:

  • Local anesthetics are medications that temporarily block sensation in a specific area of the body without affecting consciousness.

  • They are commonly used during surgical, dental, and diagnostic procedures to prevent or relieve pain.

Mechanism of Action:

1) Blocking Sodium Channels:

  • Local anesthetics block sodium channels in nerve cells, preventing electrical signal conduction and pain transmission.

2) Reversible Action:

  • The effect is temporary, and normal sensation returns once the drug wears off.

Types of Local Anesthetics:

Types of Local Anesthetics:

1) Ester Local Anesthetics (Older class)

  • Examples: Procaine, Benzocaine.

  • Metabolism: Rapidly metabolized by enzymes in the blood (plasma esterases).

  • Allergenicity: Higher risk of allergic reactions.

2) Amide Local Anesthetics (Newer class)

  • Examples: Lidocaine, Bupivacaine.

  • Metabolism: Metabolized in the liver.

  • Allergenicity: Lower risk of allergic reactions.

Forms and Administration:

1) Topical Application:

  • Applied directly to skin or mucous membranes (e.g., creams, ointments, sprays).

2) Injection:

  • Administered near nerves, into tissues, or around specific areas for profound anesthesia (e.g., nerve blocks, spinal, or epidural anesthesia).

Duration of Action:

  • Short-Acting: Procaine.

  • Intermediate-Acting: Lidocaine.

  • Long-Acting: Bupivacaine.

Uses:

  • Surgery: Numbing specific areas for minor surgical procedures.

  • Dentistry: Pain relief during tooth extractions and cavity fillings.

  • Diagnostic Procedures: Reducing discomfort during endoscopy and other tests.

  • Chronic Pain Management: Nerve blocks for chronic pain relief.

Side Effects:

  • Local Reactions: Redness, swelling, or itching at the application site.

  • Systemic Reactions: High absorption may lead to dizziness, seizures, or cardiac arrhythmias.

  • Allergic Reactions: More common with ester-type anesthetics.

Considerations:

  • Dose Control: Proper dosing minimizes risks of toxicity.

  • Adjuvants: Often combined with drugs like epinephrine to prolong effects and reduce bleeding.

  • Patient Safety: Medical history, allergies, and health conditions must be reviewed before use.


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