NEET MDS Lessons
Pharmacology
Local Anesthetics
1. Procaine (Novocaine)
a) Classic Ester type agent, first synthetic injectable local anesthetic.
b) Slow onset and short duration of action
2. Tetracaine (Pontocaine)
a) Ester type agent--ten times as potent and toxic as procaine.
b) Slow onset but long duration of action.
c) Available in injectable and topical applications.
3. Propoxycaine (Ravocaine)
a) Ester type agent–five times as potent and toxic as procaine.
b) Often combined with procaine to increase duration of action.
4. Lidocaine (Xylocaine)
a) Versatile widely used amide type agent.
b) Two - three times as potent and toxic as procaine.
c) Rapid onset and relatively long duration of action.
d) Good agent for topical application.
5. Mepivacaine (Carbocaine)
a) Amide type agent similar to lidocaine.
b) Without vasoconstrictor has only short duration of action.
6. Prilocaine (Citanest)
a) Amide type agent — less potent than lidocaine.
b) Without vasoconstrictor has only short duration of action.
c) Metabolized to o-toluidine which can cause methemoglobinemia — significant only with large doses of prilocaine.
d) Higher incidences of paresthesia reported with 4 % preparation
7. Bupivacaine (Marcaine)
a) Amide type agent of high potency and toxicity.
b) Rapid onset and very long duration of action even without vasoconstrictor.
8. Articaine (Septocaine)
a) Amide type agent
b) Only amide-type local anesthetic that contains an ester group, therefore metabolized both in the liver and plasma.
c) Approved by the FDA in 2000
d) Evidence points to improved diffusion through hard and soft tissues as compared to other local anesthetics.
e) Reports of a higher incidence of paresthesia, presumably due to the 4% concentration
f) Not recommended for use in children under 4 years of age
Ciclopirox:Ciclopirox is a synthetic antifungal agent for topical dermatologic use.
Thiazide diuretics
Chlorothiazide, Hydrochlorothiazide
Mechanism(s) of Action
1. Block facilitated Na/Cl co-transport in the early distal tubule. This is a relatively minor Na absorption mechanism and the result is modest diuresis
2. Potassium wasting effect
a. Blood volume reduction leads to increased production of aldosterone
b. Increased distal Na load secondary to diuretic effect
c. a + b = increase Na (to blood) for K (to urine) exchange which produces indirect K wasting
3. Increase distal Ca re-absorption (direct effect)
o causes an increase in plasma calcium.This is unimportant NORMALLY but makes thiazides VERY inappropriate choice for hypercalcemic patients.
4. Anti-diuretic effect in nephrogenic diabetes insipidus patients secondary to depletion of Na and Water.
Toxicity
• Electrolyte imbalance (particularly hypokalemia) ,Agranulocytosis , Allergic reactions
• Hyperuricemia , Thrombocytopenia
Neuron Basic Structure (How brain cells communicate)
• Synapse:A junction between the terminal button of an axon and the membrane of another neuron
• Terminal button(orbouton):The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to that neuron.
• Neurotransmitter:A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron.
Different types of Synapses
1-Axo-denrdritic
2-Axo-axonal
3-Axo-somatic
Chemical transmission in the CNS
The CNS controls the main functions of the body through the action endogenous chemical substances known as “neurotransmitters”.
These neurotransmitters are stored in and secreted by neurons to “transmit”information to the postsynaptic sites producing either excitatoryor inhibitory responses.
Most centrally acting drugs exert their actions at the synaptic junctions by either affecting neurotransmitter synthesis, release, uptake, or by exerting direct agonistor antagonistaction on postsynaptic sites.
Methadone
Pharmacology and analgesic potency similar to morphine.
- Very effective following oral administration.
- Longer duration of action than morphine due to plasma protein binding (t1/2 approximately 25 hrs).
- Used in methadone maintenance programs for drug addicts and for opiate withdrawal. Opiate withdrawal is more prolonged but is less intense than it is following morphine or heroin.
Benzodiazepines
All metabolites are active sedatives except the final glucuronide product.
Elimination half-life varies a great deal from drug to drug.
α-Hydroxylation is a rapid route of metabolism that is unique to triazolam,
midazolam, and alprazolam.
This accounts for the very rapid metabolism and short sedative actions of these
drugs.
Pharmacological effects of benzodiazepines
- Antianxiety.
- Sedation.
- Anticonvulsant (including drug-induced convulsions).
- Amnesia, especially drugs like triazolam.
- Relax skeletal muscle (act on CNS polysynaptic pathways).
Indications
- IV sedation, (e.g., midazolam, diazepam, lorazepam).
- Antianxiety.
- Sleep induction.
- Anticonvulsant (e.g., diazepam, clonazepam).
- Panic disorders.
- Muscle relaxation.
Adverse effects
- Ataxia, confusion.
- Excessive sedation.
- Amnesia (not a desired effect with daytime sedation).
- Altered sleep patterns (increase stage 2 and decrease stage 4 sleep).
DIURETICS
|
Specific Therapeutic Objective |
Clinical State(s) |
Drug(s) (Class) |
|
Draw fluid from tissue to vascular space reduce tissue edema |
Cerebral edema |
Mannitol (Osmotic) |
|
Decrease renal swelling |
Renal shutdown |
Glucose (Osmotic) |
|
Modest and/or sustained decrease in venous hydrostatic pressure |
Congestive heart failure |
Hydrochlorothiazide (thiazide) |
|
Aggressive and/or short-term decrease in venous hydrostatic pressure |
Congestive heart failure |
Furosemide (loop) |
|
Inhibit aldosterone action |
Hepatic cirrhosis |
triamterene (K+ sparing) |
|
Reduce potassium wasting 2o to other diuretic |
Hepatic cirrhosis |
triamterene (K+ sparing) |
|
Inhibit ADH action |
Inappropriate ADH secretion |
lithium (aquaretic) |
|
Increase calcium secretion |
Malignant hypercalcemia
|
Furosemide (loop) |
|
Reduce urine output |
Diabetes insidpidus |
Hydrochlorothiazide (thiazide) |
|
Urine alkalinization |
Various |
Carbonic anhydrase inhibitors |