LOCAL ANAESTHETICS are medications used to induce a temporary loss of sensation in a specific area of the body.
They are commonly used during surgical procedures, dental treatments, and other medical applications to prevent or alleviate pain without affecting consciousness.
Mechanism of Action:
1. Blocking Sodium Channels:
Local anesthetics work primarily by blocking sodium channels on nerve cells (neurons).
When these channels are blocked, nerve cells cannot conduct an electrical signal, which means they can't transmit pain signals to the brain.
2. Reversible Action:
This action is reversible, so once the drug wears off, normal sensation returns.
Types of Local Anesthetics:
1. Ester Local Anesthetics:
Older class, includes drugs like procaine and benzocaine.
These are generally metabolized by enzymes in the blood and can be more allergenic.
2. Amide Local Anesthetics:
Newer class, includes drugs like lidocaine and bupivacaine.
These are metabolized in the liver and typically have a lower risk of allergic reactions.
Forms and Administration:
Topical:
Applied directly to skin or mucous membranes (e.g., creams, ointments, sprays).
Injection:
Used for more profound anesthesia, injected near the nerve, into the tissue, or around a specific area (e.g., nerve blocks, spinal or epidural anesthesia).
Duration of Action:
Short-Acting:
E.g., Procaine.
Intermediate-Acting:
E.g., Lidocaine.
Long-Acting:
E.g., Bupivacaine.
Uses:
Surgery: To numb a specific area during minor surgical procedures.
Dentistry: For procedures like tooth extractions or cavity fillings.
Diagnostic Procedures: To alleviate discomfort during procedures like endoscopy.
Chronic Pain Management: In nerve blocks for chronic pain conditions.
Side Effects:
While generally safe, they can cause side effects, especially if used improperly:
Local Reactions: Redness, swelling, or itching at the application site.
Systemic Reactions: If absorbed in significant amounts, can affect the heart and central nervous system, leading to symptoms like dizziness, seizures, or cardiac arrhythmias.
Allergic Reactions: More common with ester-type anesthetics.
Considerations:
Dose: It’s crucial to use the correct dose to minimize risks.
Adjuvants: Sometimes combined with other drugs like epinephrine to prolong their effects and reduce bleeding in the area.
Patient Factors: Medical history, allergies, and specific condition considerations are essential for safe use.