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ANTIHYPERLIPIDEMIA AGENTS Plasma lipids Transported in bloodstream in form of macromolecular complexes of lipid and known as lipoproteins Two major clinical importance/sequelae of high lipid Acute pancreatitis atherosclerosis Hyperlipoproteinemia Hyperlipidemia Lipoprotein disorders Primary hypertriglyceridemias Primary chylomicronemia Familial hypertriglyceridemia Familial combined hyperlipoproteinemia Familial dysbetalipoproteinemia Primary hypercholesterolemias Famimial hypercholesterolemia Familial ligan-defective apolipoprotein B Familial combine hyperlipoproteinemia Lp(a) hyperlipoproteinemia Secondary hyperlipoproteinemia Lipid-lowering drugs Several drugs are used To decrease plasma LDL-cholesterol Drug therapy is only one approach Dietary measures are the first [...] | 19th January, 2010 | More News
Metabolism and excretion
Pharmacokinetic knowledge
Will determine of drugs of its
Route of administration
Dose
Latency of onset
Time of peak action
Duration of action
Frequency of administration
Pharmacokinetic processes
Transport of the drug across the biological membrane
Biological membrane
is a layer that acts as a barrier within or around a cell.
Thickness – 100 A0
It is a lipid bilayer.
Composed of a double layer of lipid-class molecules,
phospholipid and
cholesterol
with occasional proteins intertwined, some of which function as channels.
The polar groups (Hydrophilic) are oriented at the two surfaces and nonpolar (Hydrophobic)are embedded in the matrix
Transportation of Drugs
Drugs are transported across the membrane by
Passive diffusion and filtration
Specialized transport
Plasma:
The liquid part of the blood and lymphatic fluid, which makes up about half of its volume.
is devoid of cells and,
Has no clotting factors
contains antibodies and other proteins
Metabolism
Is is a process of chemical alteration of drug in body
Nonpolar (lipid soluble) drug Polar (Lipid insoluble)
Not reabsorbed in renal tubules
Excreted from the body.
Why drug undergoes metabolism
Drugs are consider foreign substances to body
It is a mechanism where body reacts with the substances and excretes from the body
Purpose is to protect body from ingested toxins
Primary site
Liver
Other
Kidney
Intestine
Lungs
Plasma
Metabolism may lead to
Inactivation
Drug ingested converted into inactive/less active form
Eg. Chloramphenicol, morphine
Active metabolite from an active drug
Drug converted to active metabolite
The effect of drug become more of that of parent drug
Eg. Diazepam — Desmethyl-diazepam, oxazepam
Activation of inactive drug
Prodrug
Eg Bacampicillin —- Ampicillin
Classification of metabolism/biotransformation reactions
Phase I / Nonsynthetic reaction
This results either
active metabolite or
Inactive metabolite
Phase II / Synthetic / conjugation reactions
Most of the metabolites are inactive
Phase I /Nonsynthetic reactions
Oxidation
Addition of
Oxygen or negatively charged radical
Removal of hydrogen or positively charged radical
Reduction
It is reversal of oxidation and
involves cytochrome P-450 enzymes
Hydrolysis
Addition of water (H2O)
Cyclization
Formation of ring structure
Decyclization
Open up of ring structure
Phase II / Synthetic reactions
Conjugation of drug or phase I metabolite with endogenous substrate
Derived from Carbohydrate, aminoacid
Formation of a polar ionized organic acid
Excreted in
Urine
Bile
Process in Phase II/synthetic reaction
Glucuronide conjugation
Acetylation
Methylation
Sulfate conjugation
Glycine conjugation
Glutahione conjugation
Ribonucleoside/nucleotide synthesis
References
Essentials of medical pharmacology, K.D.Tripathi
Basic and clinical pharmacology, Bertram G Katzung
About the Author
Specialized in Tropical Medicine and Research on men health especially in osteoporosis