Chapter 2, Drugs and the Body Please answer the following questions completely i
ID: 237748 • Letter: C
Question
Chapter 2, Drugs and the Body Please answer the following questions completely in 500-1000 words. Please cite your reference resources. 1. Mr. Rzepka is a 50-year-old male who has just been started on a new medication for an infection and is very confused about this medication. During morning rounds, he heard the care team mention terms including loading dose, half-life, first-pass effect, and excretion. Mr. Rzepka wants to know what these terms mean and what they have to do with his new medication Half-life First-pass effect Excretion (including the primary organ involved) How would you answer this patient's question? 2. Explain the importance of a loading dose. Why do some drugs require loading dosing and others do not? 3. Explain how each of the following factors influences drug effectiveness: Weight, Age, Gender .Explain the concepts of tolerance and cumulation and what this means for patients.Explanation / Answer
Half-life: This is the period of timerequired for the concentration or amount of drug in the body to be reduced by one- half. A drug's plasma half life depends on how quickly the drug is eliminated from the plasma.
First pass effect: The first pass effect is a phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation. This first pass effect greatly reduces the bioavailabilty of drug.
Excretion: Nonvolatile drugs are excreted mainly by renal excretion a process in which the drug passes through the kidney to the bladder and ultimately into the urine. Other ways of drug excretion may include the excretion of drug into bile, sweat, saliva, milk.
2. Importance of Loading dose
A loading dose is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose.
A loading dose is most useful for drugs that are eliminated from the body relatively slowly, i.e., have a long systemic half -life. Such drugs need only a low maintenance dose in order to keep the amount of the drug at the appropriate therapeutic level, but this also means that,without an initial higher dose, it would take a long time for the amount of the drug in the body to reach this level.
Drugs which may be started with an initial loading dose include digoxin, voriconazole, fulvestrant.
3. Factors influencing drug effectiveness
Age: The adult dose is for people between 18 and 60 years of age. The same adult dose will not prescribed for PEDIATRICS and GERIATRICS because the drug metabolizing enzymes are inefficient and hepatic metabolizing capacity is also underdeveloped, immatured renal tubular transport system in infants and the physiological functioning of geriatric population will be declined.
Gender: Menand women respond differently to same drugs. This may be due to body size and amount of body fats. Aspirin shows greater benefit in men than women in cardiovascular diseases. Testosterone increases the rate of biotransformation of drugs. Decreased metabolism of some drugs like diazepam occurs in females. Females are more susceptible to autonomic drugs because estrogen inhibits choline esterase.
Weight: Drug concentrations are dependent on the volume of distribution and clearance . Both parameters are dependent on body weight for most drugs independent of sex differences.
4. Tolerance
Drug tolerance is a pharmacological concept describing subjects reducing reaction to a drug following its repeated use. Increasing its dosage may re-amplify the drug's effects, however this may accelerate tolerance, further reducing the drug's effects. Tolerance occurs when the person no longer responds to the drug in the way that person initially responded.
Cumulation is the state at which repeated administration of a drug may produce effects that are more pronounced than those produced by the first dose.
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