PHARMACOLOGY OF LOCAL ANESTHETICS

 Characteristics

1. Block axon conduction (nerve impulse) when applied locally in appropriate concentrations.

2. Local anesthetic action must be completely reversible; however, the duration of the anesthetic block should be of sufficient length to allow completion of the planned treatment.

3. Produce minimal local toxic effects such as nerve and muscle damage as well as minimal systemic toxic effects of organ systems such as the cardiovascular and central nervous system.

Pharmacology is the study of drugs and the way they interact with living systems.  Clinical pharmacology is the study of drugs in humans.

A drug is any chemical that can effect living processes.

Therapeutics: the medical use of drugs.

An ideal drug has several important properties.  Three of these properties are of utmost importance: effectiveness, safety and selectivity. 

Effectiveness: This is the most important quality that a drug can have.  Effectiveness refers to the drug's ability to do what it is supposed to do.

Safety:  Although no drug can be totally safe, proper usage can lessen the risks of adverse effects.

Selectivity:  A truly selective drug would have no side effects, and would effect only the body process' for which it is designed and given.  Therefore, there is no such thing as a selective drug.

Pharmacokinetics: The way the body deals with a drug.  Pharmacokinetics is concerned with the processes of absorption, distribution, metabolism and excretion.

Pharmacodynamics:  What a drug does to the body.

Pharmacokinetics and pharmacodynamics are two of the processes that determine how a person will respond to a drug.  Other factors include how a drug is administered (dose, route, and timing of administration), interactions with other drugs, and individual physiological variables (weight, age, function of body systems).

Halothane (Fluothane) MAC 0.76%, Blood/gas solubility ratio 2.3
- Nonflammable.
- Any depth of anesthesia can be obtained in the absence of hypoxia.
- Halothane produces a marked hypotensive effect 
- accompanies hypotension.
- Halothane “sensitizes” the ventricular conduction system in the heart to the action of catecholamines. However, ventricular arrhythmias are rare if
- respiratory acidosis, hypoxia and other causes of sympathetic stimulation are avoided.
- Respiration is depressed by all anesthetic concentrations.
- Halothane is metabolized to a significant extent and some of its metabolic produces have been shown to be hepatotoxic.
- Can produce a malignant hyperpyrexia due to an uncontrolled hypermetabolic reaction in skeletal muscle. 

Halothane is generally used with nitrous oxide, an opiate and a neuromuscular blocking drug.

Local anesthetic selection

Local anesthetics are typically divided into 3 main categories:

short, intermediate and long acting local anesthetics.

Based on duration of the procedure and the duration of the individual agents

Short acting agents

1. Mepivacaine 3 %

2. Lidocaine 2%

Intermediate acting agents

1. Lidocaine 2% 1:100000 epi

2. Lidocaine 2% 1:50000 epi

3. Mepivacaine 2% 1:20000 neocobefrin

4. Prilocaine 4%

5. Articaine 4% 1:100000 epi

Long acting agents

1. Bupivacaine 0.5% 1:200000 epi

ANTIBIOTICS

Chemotherapy: Drugs which inhibit or kill the infecting organism and have no/minimum effect on the recipient.

Antibiotic these are substances produced by microorganisms which suppress the growth of or kill other micro-organisms at very low concentrations.

Anti-microbial Agents: synthetic as well as naturally obtained drugs that attenuate micro-organism.

SYNTHETIC ORGANIC ANTIMICROBIAL DRUGS

Sulfonamides

Trimethoprim-sulfamethoxazole

Quinolones – Ciprofloxacin

ANTIBIOTICS THAT ACT ON THE BACTERIAL CELL WALL

Penicillins

Cephalosporins

Vancomycin

INHIBITORS OF BACTERIAL PROTEIN SYNTHESIS

Aminoglycosides - Gentamicin

Antitubercular Drugs: Isoniazid & Rifampin

Tetracyclines

Chloramphenicol

Macrolides – Erythromycin, Azithromycin

Clindamycin

Mupirocin

Linezolid

 ANTIFUNGAL DRUGS

Polyene Antibiotics (Amphotericin B, Nystatin and Candicidin)

Imidazole and Triazole Antifungal Drugs

Flucytosine

Griseofulvin

ANTIPROTOZOAL DRUGS

Antimalarial Drugs – Quinine, Chloroquine, Primaquine

Other Antiprotozoal Drugs – Metronidazole, Diloxanide, Iodoquinol

 ANTIHELMINTHIC DRUGS

Praziquantel

Mebendazole

Ivermectin

ANTIVIRAL DRUGS

Acyclovir

Ribavirin

Dideoxynucleosides

Protease inhibitors

PLASMA FRACTIONS:

a) Fresh frozen plasma.

b) Platelets.

c) Plasma concentrates.

d) Non-plasma recombinant factor concentrates.