NEET MDS Lessons
Pharmacology
Pharmacokinetics
Pharmacokinetics is the way that the body deals with a drug - how that drug moves throughout the body, and how the body metabolizes and excretes it. The factors and processes involved in pharmacokinetics must be considered when choosing the most effective dose, route and schedule for a drug's use.
The four processes involved in pharmacokinetics are:
Absorption: The movement of a drug from its site of administration into the blood.
Several factors influence a drug's absorption:
- Rate of Dissolution: the faster a drug dissolves the faster it can be absorbed, and the faster the effects will begin.
- Surface Area: Larger surface area = faster absorption.
- Blood Flow: Greater blood flow at the site of drug administration = faster absorption.
- Lipid Solubility: High lipid solubility = faster absorption
- pH Partitioning: A drug that will ionize in the blood and not at the site of administration will absorb more quickly.
Distribution: The movement of drugs throughout the body.
Metabolism: (Biotransformation) The enzymatic alteration of drug structure.
Excretion: The removal of drugs from the body.
As a drug moves through the body, it must cross membranes. Some important factors to consider here then are:
Body's cells are surrounded by a bilayer of phospholipids (cell membrane).
There are three ways that a substance can cross cell membranes:
- Passing through channels and pores: only very small molecules can cross cell membranes this way.
- Transport Systems: Selective carriers that may or may not use ATP.
- Direct Penetration of the Cell Membrane:
VITAMIN -K
- Group of lipophilic, hydrophobic vitamins.
- Needed for the post-translational modification of coagulation proteins.
- Phylloquinone (vitamin K1) is the major dietary form of vitamin K.
- Vitamin K2 (menaquinone, menatetrenone) is produced by bacteria in the intestines.
Procoagulant Drugs:
Desmospressin Acetate
• Is a synthetic analogue of the pituitary antidiuretic hormone (ADH).
• Stimulates the activity of Coagulation Factor VIII
• Use for treatment of hemophilia A with factor VIII levels less than or equal to 5%, treatment of hemophilia B or in clients who have factor VIII antibodies. Treatment of severe classic von Willebrand's disease (type I) and when an abnormal molecular form of factor VIII antigen is present. Use for type IIB von Willebrand's disease.
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.
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.
CLASSICATION OF ANTICOAGULANT DRUGS
1. Direct Acting Anticoagulants
a) Calcium Chelators (sodium citrate, EDTA)
b) Heparin
2. Indirect Acting Anticoagulant Drugs
a) Warfarin
Beta - Adrenoceptor blocking Agents
These are the agents which block the action of sympathetic nerve stimulation and circulating sympathomimetic amines on the beta adrenergic receptors.
At the cellular level, they inhibit the activity of the membrane cAMP. The main effect is to reduce cardiac activity by diminishing β1 receptor stimulation in the heart. This decreases the rate and force of myocardial contraction of the heart, and decreases the rate of conduction of impulses through the conduction system.
Beta blockers may further be classified on basis of their site of action into following two main classes namely
cardioselective beta blockers (selective beta 1 blockers)
non selective beta 1 + beta 2 blockers
Classification for beta adrenergic blocking agents.
A. Non-selective (β1+β2)
Propranolol Sotalol Nadolol Timolol Alprenolol Pindolol
With additional alpha blocking activity
Labetalol Carvedilol
B. β1 Selective (cardioselective)
Metoprolol Atenolol Bisoprolol Celiprolol
C. β2 Selective
Butoxamine
Mechanisms of Action of beta blocker
Beta adrenoceptor Blockers competitively antagonize the responses to catecholamines that are mediated by beta-receptors and other
adrenomimetics at β-receptors
Because the β-receptors of the heart are primarily of the β1 type and those in the pulmonary and vascular smooth muscle are β2 receptors, β1-selective antagonists are frequently referred to as cardioselective blockers.
β-adrenergic receptor blockers (β blockers)
1. Used more often than α blockers.
2. Some are partial agonists (have intrinsic sympathomimetic activity).
3. Propranolol is the prototype of nonselective β blockers.
4. β blocker effects: lower blood pressure, reduce angina, reduce risk after myocardial infarction, reduce heart rate and force, have antiarrhythmic effect, cause hypoglycemia in diabetics, lower intraocular pressure.
5. Carvedilol: a nonselective β blocker that also blocks α receptors; used for heart failure.