NEET MDS Lessons
Pharmacology
A. Sympathetic Nervous System Depressants
1. Antagonists
Both α-adrenoceptor antagonists and β-adrenoceptor antagonists are useful antihypertensives.
- α-blocker Prazosin, phentolamine, phenoxybenzamine
- β-blocker Propranolol ,Metoprolol, atenolol
- α/β-blocker labetalol
2. Sympathetic depressants
a. Examples of peripherally acting agents include
- reserpine This agent interferes with the storage of norepinephrine
- quanethidine This agent interferes with the release of norepinephrine
- trimethaphan This agent blocks transmission through autonomic ganglia.
b. Examples of Centrally acting agents include
- alphamethyldopa
- clonidine. These agents act by decreasing the number of impresses along sympathetic nerves.
Adverse Effect
include nasal congestion, postural hypotension, diarrhea, sexual dysfunction, dry mouth. sedation and drowsiness.
B. Directly Acting Vasodilators
Act on vascular smooth muscle cells independently of adrenergic nerves and adrenergic receptors.
Relaxation of vascular smooth muscle which leads to a decrease in peripheral vascular resistance.
Sites of action of vasodilators are many. For example
Calcium Channel Blocker’s MOA
. Decrease automaticity & conduction thru SA & AV nodes
. Decreased myocardial contractility
. Decreased peripheral & coronary
smooth muscle tone = decrease SVR
Potassium channels activators
minoxidil, cause vasodilation by activating potassium channels in vascular smooth muscle.
An increase in potassium conductance results in hyperpolarization of the cell membrane which is associated with relaxation of smooth muscle.
Nitrovasodilators, such as sodium nitroprusside,
Increase in intracellular cGMP. cGMP in turn activates a protein kinase. Directly-Acting Vasodilators are on occasion used alone but more frequently are used in combination with antihypertensive agents from other classes (esp. a β-blocker and a diuretic.)
NATURAL ANTICOAGULANTS:
1. PGI-2.
2. Antithrombin.
3. Protein-C.
4. TFPI.
5. Heparin.
6. Fibrinolytic system.
Benzodiazepines
All metabolites are active sedatives except the final glucuronide product.
Elimination half-life varies a great deal from drug to drug.
?-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).
Drugs Used in Diabetes
Goals of diabetes treatment
lower serum glucose to physiologic range
keep insulin levels in physiologic range
eliminate insulin resistance
best initial step in management: weight loss, contractile-based exercise weight loss is more important for insulin sensitivity than is a low-carb diet
Modalities of diabetes treatment
Type I DM
insulin
low-sugar diet
Type II DM
exercise
diet
insulin
6 classes of drugs
Insulin
Sulfonylureas - Glyburide
Meglitinides - Nateglinide
Biguanides Metformin
Glitazones (thiazolidinediones) Pioglitazone
α-glucosidase inhibitors Acarbose
GLP-1 mimetics (incretin mimetics) Exenatide
Amylin analog Pramlintide
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
Patient positioning
The most common medical emergency encountered in the dental office setting is syncope. So patients in the supine or semi-supine position to improve venous return and cerebral blood flow provided that the position is tolerated by the patient and is appropriate for their medical condition.
Mucosal protective agents.
These are locally active agents that help heal gastric and duodenal ulcers by forming a protective barrier between the ulcers and gastric acid, pepsin, and bile salts. They do not alter the secretion of gastric acid. These drugs include sucralfate and colloid bismuth compounds. (e.g. tripotassium, dicitratobismuthate). Colloidal bismuth compounds additionally exert bactericidal action against H.pylori. Also, Prostaglandins have both antisecretory and mucosal protective effects.
Example: Misoprostol- used for prevention of NSAID – induced ulcer.
- Drugs that exert antimicrobial action against H.pylori such as amoxicillin, metronidazole, clarithromycin and tetracycline are included in the anti-ulcer treatment regimens.