NEET MDS Lessons
Pharmacology
Etomidate -Intravenous Anesthetics
- A nonbarbiturate anesthetic used primarily to induce surgical anesthesia.
- It does not produce analgesia.
- Etomidate has minimal effect on the cardiovascular system and respiration during induction of anesthesia.
- Like the barbiturates, etomidate decreases cerebral blood flow, cerebral metabolic rate and intracranial pressure.
- No changes in hepatic, renal or hematologic function have been reported.
- Myoclonic muscle movements are relatively common.
- Postoperative nausea and vomiting are more common with etomidate than with barbiturates.
CNS acting drugs are of major therapeutic and clinical importance.
They can produce diverse physiologicaland psychologicaleffects such as:
•Induction of Anesthesia
•Relief of Pain
•Prevention of Epileptic seizures
•Reduction of Anxiety
•Treatment of Parkinsonism
•Treatment of Alzheimer's disease
•Treatment of Depression
•Centrally acting drugs also include drugs that are administered without medical intervention like tea, coffee, nicotine, and opiates.
Characteristics of Opioid Receptors
mu1
Agonists : morphine phenylpiperidines
Actions: analgesia bradycardia sedation
mu2
Agonists : morphine phenylpiperidines
Actions: respiratory depression euphoria physical dependence
delta
Actions: analgesia-weak, respiratory depression
kappa
Agonists: ketocyclazocine dynorphin nalbuphine butorphanol
Actions: analgesia-weak respiratory depression sedation
Sigma
Agonists: pentazocine
Action: dysphoria -delerium hallucinations tachycardia hypertension
epsilon:
Agonists: endorphin
Actions: stress response acupuncture
Antidepressant Drugs
Drug treatment of depression is based on increasing serotonin (5-HT) or NE (or both) at synapses in selective tracts in the brain. This can be accomplished by different mechanisms.
Treatment takes several weeks to reach full clinical efficacy.
1. Tricyclic antidepressants (TCAs)
a. Amitriptyline
b. Desipramine
c. Doxepin
d. Imipramine
e. Protriptyline
2. Selective serotonin reuptake inhibitors (SSRIs)
a. Fluoxetine
b. Paroxetine
c. Sertraline
d. Fluvoxamine
e. Citalopram
3. Monoamine oxidase inhibitors (MAOIs)
a. Tranylcypromine
b. Phenelzine
4. Miscellaneous antidepressants
a. Bupropion
b. Maprotiline
c. Mirtazapine
d. Trazodone
e. St. John’s Wort
Antimania Drugs
These drugs are used to treat manic-depressive illness.
1. Lithium
2. Carbamazepine
3. Valproic acid
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
Distal (Potassium Sparing) Diuretics
Agents:
spironolactone
triamterene
Mechanism of action
Inhibition of Na/K exchange at aldosterone dependent distal tubular site
Spironolactone - competes with aldosterone for regulatory site
Triamterene - decreases activity of pump directly
• Either mechanism decreases potassium wasting
• Either mechanism produces poor diuresis (when used alone)
o relatively unimportant Na recovery site
Diurectic activity increased if:
• sodium load (body) is high
• aldosterone concentrations are high
• sodium load (tubule) is high - secondary to diuresis
Other electrolytes unaffected
Toxicity
• spironolactone may produce adrenal and sex hormone effects with LONG-TERM use
• Both drugs may produce electrolyte imbalance
ANTIDEPRESSANTS
Monoamine uptake inhibitors
1. Tricyclic antidepressants (TCAs)
2. Selective serotonin reuptake inhibitors (SSRIs)
3. Serotonin-norepinephrine reuptake inhibitors(SNRIs)
4. Norepinephrine reuptake inhibitor
Monoamine oxidase inhibitors (MAOIs)
Monoamine receptor antagonists