الفهرس 
Pharmacokinetic and Pharmacodynamic Changes in Critically Ill PatientsOnly 14 pages are availabe for public view
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Abstract
Physiologic alterations are frequently evident in critically ill patients. These alterations can significantly affect the pharmacokinetics of drugs used in this patient population. Pharmacokinetic changes can be a result of organ dysfunction, most notably the liver and kidneys, but can also be a consequence of the acute phase response, drug interactions, and therapeutic interventions. Optimal use of drugs requires a keen understanding of the potential effects of critical illness on drug absorption, distribution, metabolism, and excretion. This article outlines the major documented effects on each of these pharmacokinetic processes in critically ill patients as well as providing general strategies for drug dosing and monitoring in these patients.
Acute drug poisoning usually affects many vital organs in the body depending on the specific action of the drug and the dose ingested. It can affect the level of consciousness of different degrees, causing convulsions or severe CNS depression cardiovascular changes include arrhythmias or changes in blood pressure or pulse rate. Also respiratory changes (tachypnea, bradypnea or respiratory depression).as well as skin changes (skin discolouration or temperature change.
Similar to the management of any seriously compromised patient, the clinical approach to the patient potentially exposed to a xenobiotic begins with the recognition and treatment of life-threatening conditions: airway compromise, breathing difficulties, and circulatory problems such as hemodynamic instability and serious dysrhythmias. Once the ABC (airway, breathing, and circulation) are addressed, the patient’s level of consciousness should be assessed, as this helps determine the techniques to be used for further management of the exposure.
The management of drug poisoning should be started by history taking to identify the type and the dose of the ingested toxin. To prevent further drug absorption we can do gastrointestinal decontamination of ingested medication include initiating emesis with syrup of ipecac gastric lavage with large-bore oral or nasal gastric tubes, and administering activated charcoal with a cathartic, or whole-bowel irrigation .
The second step is enhancement of drug elimination as many toxins and drugs are weak acids or bases and are ionized in aqueous solution. The degree of Ionization is dependent on the pK, of the substance and the pH of the solution. Theoretically, alteration of urinary pH in the renal tubules promotes ionization of filtered toxins, thereby Decreasing the amount of reabsorbed toxin (cell membranes are relatively impermeable to ionized molecules).This ion trapping would thus enhance the elimination of such toxins by diuresis. Acidifying urine is no longer considered useful; however, alkalinizing urine to promote diuresis of salicylates and Phenobarbital has a limited role
Also hemodialysis can be used to remove toxins from the body and to correct acid –base and electrolyte imbalance. While hemoperfusion can remove larger molecules and highly protein bound toxins although it has no role in correction of either acid –base and electrolyte imbalance.
The toxicology laboratory is frequently viewed in much the same way as other clinical laboratories often area as a black box that converts orders into test results. Because toxicology testing volumes are relatively low and menus are extensive, testing is not as highly automated as other clinical laboratories. Many results may be hand-made the old-fashioned way.
The medical toxicologist who learns how toxicology testing is done will be able to use the results more effectively. The toxicologist who invests the time to get to know the local toxicology laboratory will have developed an invaluable resource
Diagnostic imaging can play a significant role in the management of many toxicologic emergencies. In some cases, radiographic studies can directly visualize the xenobiotic, whereas in others, they reveal the xenobiotic’s effect on various organ systems
Over the past several decades, use of the ICU and its attendant resources has led to improved survival from many serious conditions. This is the direct result of the ability to continuously monitor physiologic parameters, pay meticulous attention to supportive care, and use the most modern medical technology and treatment. Most critically ill poisoned patients have acutely reversible conditions that will clearly benefit from intensive care intervention.
In this essay there is a study of acute drug poisoning of six drugs which are among the commonly used drugs in intensive care units (Acetaminophen, Beta Adrenergic Antagonists, Calcium Channel Antagonists, Digoxin, Heparin and opiate)
The study of these drugs including Pharmacological background of each drug, mechanism of its toxicity, Clinical manifestations of its toxicity and specific management of acute toxicity of each one.