NEET MDS Lessons
Pharmacology
Effects and Toxic Actions on Organ Systems
1. Local anesthetics (dose dependent) interfere with transmission in any excitable tissue (e.g. CNS and CVS).
2. CNS effects
a. Central neurons very sensitive.
b. Excitatory-dizziness, visual and auditory disturbances, apprehension, disorientation and muscle twitching more common with ester type agents.
c. Depression manifested as slurred speech, drowsiness and unconsciousness more common with amide type agents (e.g. lidocaine).
d. Higher concentrations of local anesthetic may eventually produce tonic-clonic[grand mal] convulsions.
e. Very large doses may produce respiratory depression which can be fatal. Artificial respiration may be life-saving.
3.CVS effects
a. Local anesthetics have direct action on the myocardium and peripheral vasculature by closing the sodium channel, thereby limiting the inward flux of sodium ions.
b. Myocardium usually depressed both in rate and force of contraction. Depression of ectopic pacemakers useful in treating cardiac arrhythmias.
c. Concentrations employed clinically usually cause vasodilation in area of injection.
d. Vasoconstrictors such as epinephrine may counteract these effects on myocardium and vasculature.
4. Local Tissue Responses
a. Occasionally focal necrosis in skeletal muscle at injection site, decreased cell motility and delayed wound healing.
b. Tissue hypoxia may be produced by action of excessive amounts of vasoconstrictors.
Isoflurane (Forane) MAC 1.3%, Blood/gas solubility ratio 1.4
- Better muscle relaxation than with the other halogenated anesthetic agents.
- Isoflurane markedly potentiates the action of the neuromuscular blocking agents.
- Produces rapid onset and recovery of anesthesia.
- Does not sensitize the heart to catecholamines.
- Produces respiratory depression, but produces less cardiovascular depression
- than does halothane.
- It has an extremely low degree of metabolism and is apparently relatively
- nontoxic.
Methyl salicylate
also known as oil of wintergreen, betula oil, methyl ester) is a natural product of many species of plants Structurally, it is methylated salicylic acid It is used as an ingredient in deep heating rubs
Sulfonylureas
1st generation
tolbutamide
chlorpropamide
2nd generation
glyburide
glimepiride
glipizide
Mechanism
glucose normally triggers insulin release from pancreatic β cells by increasing intracellular ATP
→ closes K+ channels → depolarization → ↑ Ca2+ influx → insulin release
sulfonylureas mimic action of glucose by closing K+ channels in pancreatic β cells
→ depolarization → ↑ Ca2+ influx → insulin release
its use results in
↓ glucagon release
↑ insulin sensitivity in muscle and liver
Clinical use
type II DM
stimulates release of endogenous insulin
cannot be used in type I DM due to complete lack of islet function
Toxicity
first generation
disulfiram-like effects
especially chlorpropamide
second generation
hypoglycemia
weight gain
SGLT-2 Inhibitors
canagliflozin
empagliflozin
Mechanism
glucose is reabsorbed in the proximal tubule of the nephron by the sodium-glucose cotransporter 2 (SGLT2)
SGLT2-inhibitors lower serum glucose by increasing urinary glucose excretion
the mechanism of action is independent of insulin secretion or action
Clinical use
type II DM
Kinins
Peptide that are mediated in the inflammation.
Action of kinin:
On CVS: vasodilatation in the kidneys, heart, intestine, skin, and liver. It is 10 times active than histamine as vasodilator.
On exocrine and endocrine glands: kinin modulate the tone of pancreas and salivery glands and help regulate GIT motility, also affect the transport of water and electrolytes, glucose and amino acids through epithelial cell transport.
Ampicillin offered a broader spectrum of activity than either of the original penicillins and allowed doctors to treat a broader range of both Gram-positive and Gram-negative infections. Ampicillin is often used in molecular biology as a test for the uptake of genes (e.g., by plasmids) by bacteria (e.g., E. coli)