Drugs, Their Pharmacodynamics and Pharmacokinetics - Assignment Example

? Drugs, their pharmacodynamics and pharmacokinetics Drugs, their pharmacodynamics and pharmacokinetics Question 1 Orally administered drugs are introduced into the system through the mouth. They move through the digestive system till they arrive at their target sites. The drug goes through a lengthy process to get to the sites. They have to be dissolved, absorbed and metabolized based on their nature. Drugs move from the mouth where it mixes with saliva, then through the esophagus, to the stomach then finally reaches the small intestines. Here, they are absorbed into the blood through the epithelial cells and into the blood stream. From the bloodstream, they may enter the tissue fluid and then into the cell where they are metabolized and converted into active form. During this process, the drugs encounter several obstacles in their path that they have to overcome. They occur at almost every stage of the process from administering to action at the target sites. The main barriers are the cell plasma membrane, epithelial cells, endothelial cells, blood capillaries, glomerular membrane, capillaries and renal tubules among others. The plasma membrane is a lipid barrier. It only allows passage of lipophilic molecules and hydrophilic molecules, like water, into the cell. It is partially permeable to larger molecules such as larger lipophilic ones. The intestine is the main site for absorption be it drugs or food. The gastrointestinal epithelium also acts as great barrier to the movement of drugs. This layer is a single cell thick. These cells are closely packed together making it difficult to for drugs to move from the intestines into the blood stream. The layer is covered with a mucosal membrane which bars the movement and absorption of the drug. The drug has to go through two plasma membranes to get to the bloodstream. In the bloodstream, the drug is transported to various tissues where the vascular endothelium must be overcome for the drug to enter the tissue. The cells may so closely packed together that they impede the passage of large drug molecules into the tissue fluid. A good example of vessels with tightly packed epithelial cells is the capillaries at the central nervous system. The endothelial cells may also be loosely packed making it easy for the body to eliminate the drug. The spleen has ‘leaky’ epithelial lining. There is also the capillary membrane that is very selective of the size of molecules that go through. They allow movement of both polar and non-polar molecules. This is useful in the kidney during elimination of drug and waste products that are polar. The kidney is a site for drug elimination as well as re-absorption. Due to the nature of its membrane, only non-ionized and lipid compounds get reabsorbed (columbia.edu). The method of transportation also affects drug activity. Methods such as active transport require a lot of energy to perform, therefore, delaying the time of action of the drug. There could be delays in the time taken for the stomach to empty its contents into the ileum, thus, postponing absorption. Intestinal motility is also crucial when bringing the drug into contact with the cells of the epithelium for absorption. The duration of contact between the cells the drug should be adequate to promote absorption. For absorption to be successful, the flow of blood should be high for maximum absorption. Blood determines the diffusion gradient. Other factors that affect the rate of drug absorption include: the food we eat, the pH of the gastrointestinal environment, age and state of health (Washington et.al, 2000). Question 2 The half life of a drug is the time it takes to for a drug to move from full pharmacological, physiological and radioactive potency to half. This information is useful to the nurse in that is informs him or her that the drug might not be as effective. The nurse should therefore request fro the replacement of the drug with a potent one. This will ensure a patient receives proper treatment using active drugs. The drug at this point, does not give the desired effect. Ampicillin has a half life of about 1 hour. This drug is used to treat cold, flu and other viral and bacterial infections. The sample is collected and taken to the laboratory for examination and tests under the microscope. The patient showed plateau in the first hour. The patient experienced nausea and headache among other symptoms. Medication will be provided to numb the pain. Frequent trips to the lavatory should be arranged. A bucket should be provided in case the patient wants to vomit. The patient should be well fed and rehydrated. Question 3 Midazolam is a drug used to cause sleep to a patient and to block memory before a surgery. The dosage and method of administering the drug is given. This one is administered orally while another version exists that is given by injection. The effectiveness is judged by the speed of the patient to fall asleep and stay that way for the rest of the procedure. The patient should also have little or no recollection of the surgery. The objective data is obtained from looking at the patient and contact with their bodies. Subjective data involve talking with the patient before the procedure to find out if the drug is effective and after to see if the medication made them forget. Question 4 Tetracycline Hydrochloride Oral capsule are commonly given to patients with bacterial infections like flu. The drug id administered orally from where it goes to the stomach then to the intestines. It is absorbed into the blood then travels to the respiratory tract where it acts against the bacteria. The patient in question is a child aged 12 years. He presented the symptoms related to flu such as fever, headache, dry cough, weakness and watery discharge from the nose to name a few. After the description, samples were taken and studied under a microscope using the gram staining technique. The results showed positive for flu. The flu virus is very contagious and the patient probably contracted it from someone else. She mentioned she say next to a man who had been coughing on the train some days back. She has no prior allergies to this medication and has not contacted the flu recently (plateaudrugs.com). Question 5 Tetracycline fights bacteria by inhibiting protein synthesis in the bacteria. the bacteria then die due to lack of formation of essential proteins. The drug has components that enter the bacterial body and execute this function (Tozer & Rowland. 2006). The effects brought about by this drug include: tooth discoloration, fever, pain on swallowing, rectal or genital irritation, weakness or tiredness, white patches or sores in the mouth, yellowing eyes and skin. These are some of the effects the drug might illicit from a user. Pregnant women and women on birth control pills are some of the people advised against using this drug in that period. References Drug absorption. (n.d.). columbia.edu. Retrieved November 15, 2013, from http://www.columbia.edu/itc/gsas/g9600/2004/GrazianoReadings/Drugabs.pdf Wellness Center - Plateau DrugCenter. (n.d.). Wellness Center - Plateau DrugCenter. Retrieved November 14, 2013, from http://www.plateaudrugs.com/wellness-center/ Kar, A. (2011). Essentials of biopharmaceutics and pharmacokinetics. New Delhi: Elsevier. Tozer, T. N., & Rowland, M. (2006). Introduction to pharmacokinetics and pharmacodynamics: The quantitative basis of drug therapy. Philadelphia: Lippincott Williams & Wilkins. Washington, N., Washington, C. G., & Wilson, C. (2000). Physiological Pharmaceutics: Barriers to Drug Absorption. London: CRC Press. Read More