NEET MDS Lessons
Pharmacology
Lithium carbonate: 1st choice (controls mania in bipolar disorders); delay before onset of therapeutic benefit; no psychotropic effects in normal humans
i. Mechanism: blocks enzymes in inositol phosphate signaling pathway; no consistent effects of lithium on NE, 5-HT, and DA
ii. Side effects: severe CNS (ataxia, delirium, coma, convulsions) and CV (cardiac dysrhythmias)
Classification
I) Esters
1. Formed from an aromatic acid and an amino alcohol.
2. Examples of ester type local anesthetics:
Procaine
Chloroprocaine
Tetracaine
Cocaine
Benzocaine- topical applications only
2) Amides
1. Formed from an aromatic amine and an amino acid.
2. Examples of amide type local anesthetics:
Articaine
Mepivacaine
Bupivacaine
Prilocaine
Etidocaine
Ropivacaine
Lidocaine
Organic Nitrates
Relax smooth muscle in blood vessel
Produces vasodilatation
– Decreases venous pressure and venous return to the heart Which decreases the cardiac work load and oxygen demand.
– May have little effect on the coronary arteries CAD causes stiffening and lack of
– responsiveness in the coronary arteries
– Dilate arterioles, lowering peripheral vascular resistance Reducing the cardiac workload
Main effect related to drop in blood pressure by
– Vasodilation- pools blood in veins and capillaries, decreasing the volume of blood that the heart has to pump around (the preload)
– relaxation of the vessels which decreases the resistance the heart has to pump against (the afterload)
Indications
- Myocardial ischemia
– Prevention
– Treatment
Nitroglycerin (Nitro-Bid)
• Used
– To relive acute angina pectoris
– Prevent exercise induced angina
– Decrease frequency and severity of acute anginal episodes
Type
• Oral - rapidly metabolized in the liver only small amount reaches circulation
• Sublingual – Transmucosal tablets and sprays
• Transdermal – Ointment s
– Adhesive discs applied to the skin
• IV preparations
Sublingual Nitroglycerine
• Absorbed directly into the systemic circulation, Acts within 1-3 minutes , Lasts 30-60 min
Topical Nitroglycerine
• Absorbed directly into systemic circulation, Absorption at a slower rate. , Longer duration of action
Ointment - effective for 4-8 hours
Transdermal disc - effective for 18-24 hours
Isosorbide dinitrate
• Reduces frequency and severity of acute anginal episodes
• Sublingual or chewable acts in 2 min. effects last 2-3 hours
• Orally, systemic effects in about 30 minutes and last about 4 hours after oral administration
Tolerance to Long-Acting Nitrates
• Long-acting dosage forms of nitrates may develop tolerance
– Result in episodes of chest pain
– Short acting nitrates less effective
Prevention of Tolerance
• Use long-acting forms for approximately 12-16 hours daily during active periods and omit them during inactive periods or sleep
• Oral or topical should be given every 6 hours X 3 doses allowing a rest period of 6 hours
Isosorbide dinitrate (Isordil, Sorbitrate) is used to reduce the frequency and severity of acute anginal episodes.
When given sublingually or in chewable tablets, it acts in about 2 minutes, and its effects last 2 to 3 hours. When higher doses are given orally, more drug escapes metabolism in the liver and produces systemic effects in approximately 30 minutes. Therapeutic effects last about 4 hours after oral administration
Isosorbide mononitrate (Ismo, Imdur) is the metabolite and active component of isosorbide dinitrate. It is well absorbed after oral administration and almost 100% bioavailable. Unlike other oral nitrates, this drug is not subject to first-pass hepatic metabolism. Onset of action occurs within 1 hour, peak effects occur between 1 and 4 hours, and the elimination half-life is approximately 5 hours. It is used only for prophylaxis of angina; it does not act rapidly enough to relieve acute attacks.
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
Local anesthetic selection
Local anesthetics are typically divided into 3 main categories:
short, intermediate and long acting local anesthetics.
Based on duration of the procedure and the duration of the individual agents
|
|
Infiltration |
Nerve block |
||
|
|
Pulpal |
Soft tissue |
Pulpal |
Soft tissue |
|
Short |
30 min |
2-3 hrs |
45 min |
2-3 hrs |
|
Intermediate |
60 min |
2-3 hrs |
75-90 min |
3-4 hrs |
|
Long |
40 min |
5-6 hrs |
3-4 hrs |
6-8 hrs |
Short acting agents
1. Mepivacaine 3 %
2. Lidocaine 2%
Intermediate acting agents
1. Lidocaine 2% 1:100000 epi
2. Lidocaine 2% 1:50000 epi
3. Mepivacaine 2% 1:20000 neocobefrin
4. Prilocaine 4%
5. Articaine 4% 1:100000 epi
Long acting agents
1. Bupivacaine 0.5% 1:200000 epi
CLASSICATION OF ANTICOAGULANT DRUGS
1. Direct Acting Anticoagulants
a) Calcium Chelators (sodium citrate, EDTA)
b) Heparin
2. Indirect Acting Anticoagulant Drugs
a) Warfarin
Class IV Calcium Channel Blockers
• Block the movement of calcium into conductile and contractile myocardial cells
• Treatment: treatment of supraventricular tachycardia
– Diltiazem
– Verapamil
Adverse Effects
• Adverse effects associated with vasodilation of blood vessels throughout the body.
• CNS – dizziness, weakness, fatigue, depression and headache,
• GI upset, nausea, and vomiting.
• Hypotension CHF, shock arrhythmias, and edema