NEET MDS Lessons
Pharmacology
FUNDAMENTALS OF INJECTION TECHNIQUE
There are 6 basic techniques for achieving local anesthesia of the structures of the oral cavity:
1. Nerve block
2. Field block
3. Infiltration/Supraperiosteal
4. Topical
5. Periodontal ligament (PDL)
6. Intraosseous
Nerve block- Nerve block anesthesia requires local anesthetic to be deposited in close proximity to a nerve trunk. This results in the blockade of nerve impulses distal to this point. It is also important to note that arteries and veins accompany these nerves and can be damaged. To be effective, the local anesthetic needs to pass only through the nerve membrane to block nerve conduction Field block/Infiltration/Supraperiosteal - Field block, infiltration and supraperiosteal injection techniques, rely on the ability of local anesthetics to diffuse through numerous structures to reach the nerve or nerves to be anesthetized:
- Periosteum
- Cortical bone
- Cancellous bone
- Nerve membrane
Topical - Topical anesthetic to be effective requires diffusion through mucous membranes and nerve membrane of the nerve endings near the tissue surface
PDL/Intraosseous - The PDL and intraosseous injection techniques require diffusion of local anesthetic solution through the cancellous bone (spongy) to reach the dental plexus of nerves innervating the tooth or teeth in the immediate area of the injection. The local anesthetic then diffuses through the nerve membrane
Dental implications of these drugs:
1. Adverse effects: gingival hyperplasia (phenytoin), osteomalacia (phenytoin, Phenobarbital), blood dyscrasias (all but rare)
2. Drug interactions: additive CNS depression (anesthetics, anxiolytics, opioid analgesics), induction of hepatic microsomal enzymes (phenytoin, Phenobarbital, carbamazepine), plasma protein binding (phenytoin and valproic acid)
3. Seizure susceptibility: stress can → seizures
Loperamide
- Similar chemically and pharmacologically to Diphenoxylate.
- Slows gastrointestinal motility by effects on the circular and longitudinal muscles of the intestine.
- Not well absorbed following oral administration.
- Useful in the treatment of diarrhea.
CLASSICATION OF ANTICOAGULANT DRUGS
1. Direct Acting Anticoagulants
a) Calcium Chelators (sodium citrate, EDTA)
b) Heparin
2. Indirect Acting Anticoagulant Drugs
a) Warfarin
Structure of the CNS
The CNS is a highly complex tissue that controls all of the body activities and serves as a processing center that links the body to the outside world.
It is an assembly of interrelated “parts”and “systems”that regulate their own and each other’s activity.
1-Brain
2-Spinal cord
The brain is formed of 3 main parts:
I. The forebrain
• cerebrum
• thalamus
• hypothalamus
II. The midbrain
III. The hindbrain
• cerebellum
• pons
• medulla oblongata
Different Parts of the Different Parts of the CNS & their functions CNS & their functions
The cerebrum(cerebral hemispheres):
It constitutes the largest division of the brain.
The outer layer of the cerebrum is known as the “cerebral cortex”.
The cerebral cortex is divided into different functional areas:
1.Motorareas(voluntary movements)
2.Sensoryareas(sensation)
3.Associationareas(higher mental activities as consciousness, memory, and behavior).
Deep in the cerebral hemispheres are located the “basal ganglia” which include the “corpus striatum”& “substantianigra”.
The basal gangliaplay an important role in the control of “motor”activities
The thalamus:
It functions as a sensory integrating center for well-being and malaise.
It receives the sensory impulses from all parts of the body and relays them to specific areas of the cerebral cortex.
The hypothalamus:
It serves as a control center for the entire autonomic nervous system.
It regulates blood pressure, body temperature, water balance, metabolism, and secretions of the anterior pituitary gland.
The mid-brain:
It serves as a “bridge”area which connects the cerebrum to the cerebellum and pons.
It is concerned with “motor coordination”.
The cerebellum:
It plays an important role in maintaining the appropriate bodyposture& equilibrium.
The pons:
It bridges the cerebellum to the medulla oblongata.
The “locus ceruleus”is one of the important areas of the pons.
The medulla oblongata:
It serves as an organ of conduction for the passage of impulses between the brain and spinal cord.
It contains important centers:
• cardioinhibitory
• vasomotor
• respiratory
• vomiting(chemoreceptor trigger zone, CTZ).
The spinal cord:
It is a cylindrical mass of nerve cells that extends from the end of the medulla oblongata to the lower lumbar vertebrae.
Impulses flow from and to the brain through descending and ascending tracts of the spinal cord.
Gabapentin (Neurontin): newer; for generalized tonic-clonic seizures and partial seizures (partial and complex)
Mechanism: unknown but know doesn’t mimic GABA inhibition or block Ca currents
Side effects: dizziness, ataxia, fatigue; drug well-tolerated and no significant drug interactions
Pharmacodynamics
Pharmacodynamics is the study of what drugs do to the body and how they do it.
Dose-Response Relationships
- Basic Features of the Dose-Response Relationship: The dose-response relationship is graded instead of all-or-nothing (as dose increases, response becomes progressively larger).
- Maximal Efficacy and Relative Potency
- Maximal Efficacy: the largest effects that a drug can produce
- Relative Potency: Potency refers to the amount of drug that must be given to elicit an effect.
- Potency is rarely an important characteristic of a drug.
- Potency of a drug implies nothing about its maximal efficacy.