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:
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.