NEET MDS Lessons
Pharmacology
Mefenamic acid
Analgesic, anti‐inflammatory properties less effective than aspirin
Short half‐lives, should not be used for longer than one week and never in pregnancy and in children.
Enhances oral anticoagulants
Used to treat pain, including menstrual pain. It decreases inflammation (swelling) and uterine contractions.
Fifth Generation:
These are extended spectrum antibiotics.
Ceftaroline, Ceftobiprole
Glucocorticoids
Cortisol (hydrocortisone) and its synthetic derivatives
|
Drug |
Duration |
| Cortisol | Short |
| Prednisone | Medium |
| Triameinolone | Intermediate |
| Betamethasone | Long |
| Dexamethasone | Long |
Mechanism
↓ the production of leukotrienes and prostaglandins - inhibits phospholipase A2 , inhibits expression of COX-2 , will also stimulate the bone marrow to produce neutrophils resulting in leukocytosis
halts inflammatory cascade
↓ leukocyte migration
↓ capillary permeability
↓ phagocytosis
↓ platelet-activating factor
↓ interleukins (e.g. IL-2)
may trigger apoptosis in dividing and non-dividing cells
used in cancer chemotherapy
Clinical use
anti-inflammatory
immunosuppression
cancer chemotherapy (prednisone most common)
CLL
Hodgkin's lymphomas
part of MOPP regimen
Addison disease
asthma
Toxicity
1) must taper dose to avoid toxicity
2) suppression of ACTH → shock state if abrupt withdrawal - > cortical atrophy, malaise, myalgia, arthralgia, fever
3) iatrogenic Cushing syndrome ->buffalo hump, moon facies, truncal obesity, muscle weakness and atrophy, thin skin, easy bruising, acne
4) osteoporosis - vertebral fractures, aseptic hip necrosis, ↓ skeletal growth in children
5) hyperglycemia (diabetes) -due to ↑ gluconeogenesis , glaucoma, cataracts, and other complications can subsequently result
6) ↑ GI acid release -ulcers
7) Na+ retention -> edema, HTN, hypokalemia alkalosis, hypocalcemia
8)↓ wound healing
9) ↑ infections
10) mental status changes
11) cataracts
Anticonvulsants: include carbamazepine (use when lithium not tolerated; may not be as effective) .
valproic acid (use when lithium not tolerated; rapid onset)
Methods of general anesthesia
CIRCLE SYSTEM
*HIGH-FLOW
FRESH GAS FLOW > 3 l/min.
*LOW-FLOW
FGF ok. 1l/min.
*MINIMAL-FLOW
FGF ok. 0,5 l/min.
TCI -Target Controlled Infusion
TCI is an infusion system which allows the anaesthetist to select the target blood concentration required for a particular effect and then to control depth of anaesthesia by adjusting the requested target concentration
Mechanism
Instead of setting ml/h or a dose rate (mg/kg/h), the pump can be programmed to target a required blood concentration.
• Effect site concentration targeting is now included for certain pharmacokinetic models.
• The pump will automatically calculate how much is needed as induction and maintenance to maintain that concentration.
Benzodiazepines (BZ):
newer; depress CNS, selective anxiolytic effect (no sedative effect); are not general anesthetics (but does produce sedation, stupor) or analgesics
BZ effects:
1. Central: BZs bind GABAA receptors in limbic system (amygdala, septum, hippocampus; involved in emotions) and enhance inhibition of neurons in limbic system (this may produce anxiolytic effects of BZs)
a. GABA receptor: pentameric (α, β, δ, γ subunits)
i. Binding sites: GABA (↑ conductance (G) of Cl-, hyperpolarization, inhibition), barbiturate (↑ GABA effect), benzodiazepine (↑ GABA effect), picrotoxin (block Cl channel)
b. GABA agonists: GABA (binds GABA → Cl influx; have ↑ frequency of Cl channel opening; BZs alone- without GABA don’t affect Cl channel function)
c. Antagonists: bicuculline (competitively blocks GABA binding; ↓ inhibition,→ convulsions; no clinical use), picrotoxin (non-competitively blocks GABA actions, Cl channel → ↓ inhibition → convulsions)
2. Other agents at BZ receptor:
a. Agonists: zolpidem (acts at BZ receptor to produce pharmacological actions)
b. Inverse agonists: β-carbolines (produce opposite effects at BZ binding site-- ↓ Cl conductance; no therapeutic uses since → anxiety, irritability, agitation, delirium, convulsions)
3. Antagonists: flumazenil (block agonists and inverse agonists, have no biological effects themselves; can precipitate withdrawal in dependent people)
Metabolism: many BZs have very long action (since metabolism is slow); drugs have active metabolites
2 major reactions: demethylation and hydroxylation (both very slow reactions)
Fast reaction: glucuronidation and urinary excretion
Plasma half life: long (for treating anxiety, withdrawal, muscle relaxants), intermediate (insomnia, anxiety), short (insomnia), ultra-short (<2hrs; pre-anesthetic medication)
Acute toxicity: very high therapeutic index and OD usually not life threatening (rarely see coma or death)
Treatment: support respiration, BP, gastric lavage, give antagonist (e.g., glumazenil; quickly reverses BD-induced respiratory depression)
Tolerance: types include pharmacodynamic (down-regulation of CNS response due to presence of drug; this is probably the mechanism by which tolerance develops), cross-tolerance (with other BZ and CNS depressants like EtOH and BARBS), acquisition of tolerance (tolerance develops fastest in anticonvulsant > sedation >> muscle relaxant > antianxiety; means people can take BZs for long time for antianxiety without → tolerance)
Physical dependence: low abuse potential (no buz) but physical/psychological dependence may occur; physical dependence present when withdrawal symptoms occur (mild = anxiety, insomnia, irritability, bad dreams, tremors, anorexia; severe = agitation, depression, panic, paranoia, muscle twitches, convulsions)
Drug interactions: minimally induce liver enzymes so few interactions; see additive CNS depressant effects (can be severe and → coma and death if BZs taken with other CNS depressants like ethanol)