But when is it better to use the alligation approach as opposed to the algebraic method? Before I tell you, let us take a look at this interesting concentration questions and see how it illustrates an important concept regarding when it is better to use the alligation method. Now, there are two ways you can solve this problem. For these types of problems where you have two concentrations and the desired concentration falls between the two concentrations, the alligation approach actually works better than the algebraic method. It is typically faster. See step-by-step solution in the video and keep reading.
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The calculation is set up in Figure 6. Figure 6 1. Now, these numbers need to be converted to a measurable quantity, such as grams. How much 2. Using a ratio method: The number of 2. To ensure safe, effective treatment for patients, a weight-based dosing method is often used for populations such as pediatric or elderly patients, and it is in the prescribing information for many medications.
Therefore, it is important that pharmacy technicians are aware that 1 kg is equal to 2. Following is an example of how to accurately individualize drug dosing using actual body weight. Example For the above prescription, the patient weighs 30 lb.
Calculate the correct dose and needed amount for the patient using actual body weight. This problem can be solved using a variety of methods, including setting up a fractional equation, ratio-proportion, and DA.
A 60 mL bottle is in stock. This product can be used with the instructions to discard the remaining amount after the 7 day course of therapy is complete. Body Surface Area BSA BSA is generally considered the most accurate method used to calculate drug doses because it is a mathematical function of height and weight. BR weighs lb and is 68 in tall.
Step 1: Based on the information provided in the above order, use the inches and pounds method for calculating BSA. The next example uses the metric system.
JM weighs 78 kg and is cm tall. Step 1: Based on the information provided in the above order, use the kg and cm calculation for determining BSA. Example: JT is a year-old man weighs 89 kg and is 75 inches tall.
Step 1: Determine the number of inches JT is over 5 feet. Example: MT is a year-old man who presents to the emergency room ER with the chief complaint of unrelenting fever for the past 24 hours. He indicates that he has been taking mg of acetaminophen around the clock with no relief and that he does not take any other medications. After careful deliberation, the ER physician diagnoses MT with fever of unknown origin and elects to empirically treat for viral encephalitis.
To use the formula to calculate IBW the height must be converted to inches. These types of drugs are often referred to as polar or hydrophilic, meaning that they have a high affinity for water.
The recommendation is to use an ABW when calculating dosages with these drugs especially for obese patients because dosing these medications according to IBW may result in suboptimal dosages. Adipose tissue does contain some water. This dose increase is most often performed with the use of a correction factor, such as 0. Notably, the ABW formula is the same for both men and women; but the correction factor may vary, depending on the antibiotic that is used. Example: CJ is a year-old man who weighs kg and is 70 inches tall.
Calculate his ABW. Step 1: First, calculate his IBW. Example: JR is a year-old man who presents to the emergency department ED with altered mental status and pain during urination. JR is lb and is 64 in tall. The rate can be found using dimensional analysis. Rates may be presented as mL per minute or drops gtts per minute.
Providers may order IV medication as the amount of drug in mg, mcg, or units to administer per minute or hour. In the hospital setting, it may be necessary to determine the drip rate based on this information or the volume needed to supply a patient with the necessary amount of medication or fluid.
In the course of their duties, pharmacy technicians in hospitals may be required to verify drip rate doses for patient safety, to enhance patient care, and to minimize drug waste. What rate would deliver the correct dose to the patient in mL per minute?
This can be found using several methods. For this example, a ratio will be used. Occasionally, the rate may be needed in drops per minute. The following equation can be used if this type of rate needs to be found. Example: A provider orders 1 L of 0. Step 2: Next, convert the time from hours to minutes. Step 3: Then, use the equation above to solve for the IV drip rate. Another calculation related to drip rates is to determine the total volume that is needed for a patient to deliver the required amount of a drug or to last for a specific amount of time.
What volume will be needed for this patient? Step 1: For this calculation, simply multiply the rate by the amount of time, making sure that the units cancel to leave you with volume. Moreover, an increasing number of State Boards of Pharmacy have recognized the integral role of pharmacy technicians and have revised practice regulations to allow an increase in their responsibilities. Scope of contemporary pharmacy practice: roles, responsibilities, and functions of pharmacists and pharmacy technicians.
J Am Pharm Assoc. Zentz LC. Math for Pharmacy Technicians. Louis, MO: Elsevier; Basicmedicl Key website. June1, Accessed July Bank E. How to Calculate Aliquot. Sciencing website. April 24, Pharmaceutical Calculations. Weight-based dosing in medication use: what should we know? Patient Prefer Adherence. Pai MP. Drug dosing based on weight and body surface area: mathematical assumptions and limitations in obese adults.
Antimicrobial dosing in obese patients. Clin Infect Dis. Pharmacy Calculations. April University of Kentucky Healthcare Pharmacy Services website. Calculating Intravenous Flow Rates. ATI Nursing Education website. Published April 14, Human Resources for Health Web site.
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It is highly useful for the pharmacy technicians to quickly estimate alligation ratio and then to prepare solutions of desired concentration from available stock solutions. Is this method different from dilution? Yes,of course, but not completely different. When water is used as one of the solvent alligation simply becomes a dilution technique. In all other cases, alligation plays unique role in pharmacy calculations.
How to do it - Step #1
Sodium Chloride Equivalent Method