7. Ion Trapping cont: Body fluids where a pH difference from blood pH will favor trapping or reabsorption: stomach contents small intestine breast milk aqueous humor (eye) vaginal secretions prostatic secretions www.freelivedoctor.com
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20. First-pass Effect cont. Magnitude of first pass hepatic effect: Extraction ratio (ER) ER = CL liver / Q ; where Q is hepatic blood flow (usually about 90 L per hour. Systemic drug bioavailability (F) may be determined from the extent of absorption (f) and the extraction ratio (ER): F = f x (1 -ER) www.freelivedoctor.com
22. Rectal 1. unconscious patients and children 2. if patient is nauseous or vomiting 3. easy to terminate exposure 4. absorption may be variable 5. good for drugs affecting the bowel such as laxatives 6. irritating drugs contraindicated www.freelivedoctor.com
26. Intravascular Absorption phase is bypassed (100% bioavailability) 1.precise, accurate and almost immediate onset of action, 2. large quantities can be given, fairly pain free 3. greater risk of adverse effects a. high concentration attained rapidly b. risk of embolism c. OOPS factor or !@#$% www.freelivedoctor.com
27. Intramuscular 1. very rapid absorption of drugs in aqueous solution 2.repository and slow release preparations 3.pain at injection sites for certain drugs www.freelivedoctor.com
28. Subcutaneous 1. slow and constant absorption 2. absorption is limited by blood flow, affected if circulatory problems exist 3. concurrent administration of vasoconstrictor will slow absorption www.freelivedoctor.com
29. Inhalation 1.gaseous and volatile agents and aerosols 2.rapid onset of action due to rapid access to circulation a.large surface area b.thin membranes separates alveoli from circulation c.high blood flow Particles larger than 20 micron and the particles impact in the mouth and throat. Smaller than 0.5 micron and they aren't retained. www.freelivedoctor.com
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35. The ROA is determined by the physical characteristics of the drug, the speed which the drug is absorbed and/ or released, as well as the need to bypass hepatic metabolism and achieve high conc. at particular sites www.freelivedoctor.com Important Info
36. No single method of drug administration is ideal for all drugs in all circumstances Very Important Info! www.freelivedoctor.com
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