Drug idiosyncrasy

Drug idiosyncrasy - Part I

Pharmacogenetic variation has been identified in drug metabolism (acetylation, cytochrome P450 variants, plasma cholinesterase variants), inability to compensate for drug effects (G6PD, acute porphyrias) and in drug effects themselves (malignant hyperthermia). Each of the examples will be discussed separately.

Acetylator status

Acetylation is one of the non-microsomal phase II conjugation reactions. The gene controlling the enzyme N-acetyltransferase, exists in one of two forms that determines the acetylator status of an individual which can be slow or fast. The prevalence of slow acetylation is 60% in Caucasians and 10-20% in Asians. Drugs subject to N-acetylation include isoniazid, hydralazine, procainamide, some sulphonamides, sulphasalazine, nitrazepam, and caffeine. Slow acetylators are at higher risk of side effects of these drugs such as peripheral neuropathy with isoniazid, lupus syndrome with hydralazine and procainamide, allergic reactions and hemolysis with sulphonamides and gastroinstetinal side effects with sulphasalazine

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The pressure volume loop...

In the pressure-volume loop below, cardiac work is best represented by: the area of the curve the slope of the line from points C to D the distance of the line from points C to D the slope of a line from points A to D .. .. ... .... ... .... .... .... In the pressure-volume loop below, cardiac work is best represented by: the area of the curve Cardiac work is the product of pressure and volume and is linearly related to myocardial oxygen consumption. Cardiac work is best represented by the area of the curve of a pressure-volume loop.

Anaphylaxis updates part 2- Empty Ventricle Syndrome

Patients with anaphylaxis should not suddenly sit, stand, or be placed in the upright position. Instead, they should be placed on the back with their lower extremities elevated or, if they are experiencing respiratory distress or vomiting, they should be placed in a position of comfort with their lower extremities elevated. This accomplishes 2 therapeutic goals: 1) preservation of fluid in the circulation (the central vascular compartment), an important step in managing distributive shock; and 2) prevention of the empty vena cava/empty ventricle syndrome, which can occur within seconds when patients with anaphylaxis suddenly assume or are placed in an upright position. Patients with this syndrome are at high risk for sudden death. They are unlikely to respond to epinephrine regardless of route of administration, because it does not reach the heart and therefore cannot be circulated throughout the body

Steroids In Perioperative period...The Multi-purpose Drugs

1-Steroids are not Bronchodilator ,but have well established usefulness in hyper-reactive airway. They are also said to have a permissive role for bronchodilator medication. They can be administered orally, parenterally or in aerosol form 2- Steroids have been commonly used in chemotherapy for prevention of nausea along with other anti-emetic agents . Dexamethasone was found to be highly effective when given immediately before induction rather than at the end of anesthesia . 3- Steroids do exert analgesic effects. Various routes of administration of steroids include parentral, local infiltration at operated site , as an adjuvant in nerve blocks and central-neuraxial blockade. 4 - Steroids cannot be the mainstay of therapy in anaphylaxis because of the delayed onset of action, so they are used as adjunct after initial treatment with epinephrine. 5- Steroids (Dexamethsone) are of value in reduction or prevention of cerebral edema associated with parasitic infections and neopla...

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