Drug Calculation Review

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Introduction 

When hearing about drug calculations, what comes to mind? If you’re a nurse, you’ve definitely heard of drug calculations before. You probably spend hundreds of hours performing drug calculations between your nursing studies and career. Between patient care and even in your personal life, drug calculations are one of the most essential skills for nurses of all specialties and certifications. The information in the course will serve as a valuable resource for nurses regarding drug calculations.  

Defining Drug Calculations 

Drug calculations are the calculations needed to administer the correct dosage to the correct patient at the correct time with the correct route. They can be performed anywhere drugs are administered, such as inpatient settings, outpatient settings, and more. Drug calculations can be needed for medications of all types, such as intravenous fluids, oral tablets, and injections. 

Nurses of all certifications and specialties can administer drugs, as this is one of the most common tasks for nurses. Depending on each state and workplace regulations, certain certified or licensed nurses can administer certain medications. Even with the rise of workplace technologies, such as electronic health records (EHRs), drug calculators in workplace devices, and more, knowing how to perform a drug calculation is essential for all nurses. Regardless of the workplace technology, it is ultimately the responsibility of the nurse to assess the accuracy of the drug calculation given the provider’s order, medication options, and patient condition (1,2,3).  

Core Concepts of Drug Calculations: Reducing Medication Administration Errors 

Medication administration errors have existed for decades in healthcare and are often a major source of stress, concern, safety, and liability for all healthcare workers. Patients are also severely concerned about medication administration errors, given that they are in the care of healthcare workers and rely on healthcare to provide appropriate care. Medication administration errors are some of the most common complications in healthcare and result in over a billion dollars in healthcare complications. As a result of this common concern and the livelihood and safety of patients, nurses must be aware of how to reduce medication administration errors (2,3).  

Common ways to reduce medication administration errors include:  

• Ensuring the order is complete before administration of medication 

• Ensuring the patient’s allergies and health history are up to date in the medical records 

• Confirming your workplace’s policies and training on medication administration 

• Performing drug calculations and medication administrations with little to no distractions 

Core Concepts of Drug Calculations: Role of Medication Dosage Calculations and Patient Safety 

Medication dosage calculations are essential to patient safety. Several aspects of nursing care require medication administration. To properly administer a medication, the nurse must be aware of the role of medication dosage calculations. For instance, some medications are weight dependent, causing a patient who might be more obese to require a higher dose for a therapeutic effect to occur.  

Other medications might have special calculations depending on the rate of multiple infusions at once. Because of the varied routes of medication administration, various dosages, and several concerns related to patient safety. 

Here are some tips to consider regarding medication dosage calculations and patient safety (1,2,3,4): 

• Be familiar with the medication before calculation and administration  

• Monitor the patient to determine if the medication is having the desired response 

• Ask the patient how they are feeling with the medication regarding their symptoms 

• Confirm medication dosage calculations with your workplace’s technology and also by your calculations 

• Ask for a second nurse’s opinion on a drug calculation if needed 

• Clarify the provider’s order if the calculation does not appear within the expected range for the patient and their condition (or if the patient is not having the desired therapeutic response) 

Core Concepts of Drug Calculations: Background on Medication Dosage Education in Nursing School 

Nursing schools across America regularly teach nursing students about medication dosage, often multiple times a semester well until graduation. In fact, medication dosage is often a pillar in determining the competency of a future nurse before graduation. Studies have shown that nursing students often struggle with more complex medication dosage calculations and when there are various units of measurement involved. Most students understand the basics of drug calculations but can often be confused by drip rates, weight, and unit conversions.  

In simulated clinical scenarios, students felt pressured by time, patient need, and simulated workplace dynamics regarding medication dosage, leading to possible errors in real-time clinical care. To address these concerns, nursing schools need to perform more education on medication dosing, provide more opportunities to practice medication dosage calculations outside of the clinical setting and provide a wider variety of teaching methods to boost students’ confidence (1,2,3,4). 

Core Concepts of Drug Calculations: Drug Calculation Formulas and Examples 

There are several examples of drug calculations, as there are hundreds of medications and various ways to administer medications. Typically, the most common approaches to drug calculations include ratio proportion, dimensional analysis, and the desired over-have method. A solid understanding of drug calculation formulas also means understanding unit conversions as well, such as tablespoon to milliliters, pint to ounces, and pounds to kilograms (1,3,4).  

An example of the ratio proportion method is the amount on hand/quantity you have = desired Amount / x [x represents the quantity you need].  

• A provider orders lorazepam 6 mg IV push now for an irate patient in the emergency room. There are several 4 mg/mL vials available from the pharmacy. How many mL are required to carry out the correct ordered dose? 

• Amount on hand/quantity you have = desired Amount / x [x represents the quantity you need] 

• • 4mg/ 1 mL = 6mg/ x mL 

• • 4x = 6 

• • X = 1.5 mL needed to administer to the patient 

An example of the desired over-have method is setting up a formula or equation to solve for any unknown amount (commonly known as x).  

Desire amount = ordered dose amount/amount on Hand x Quantity. 

• A provider requests morphine 10 mg IV Push for a patient in the emergency room in severe pain after falling down the stairs. The pharmacy has 2 mg/mL vials on hand. How many milliliters should the nurse draw up in a syringe to deliver the desired dose? 

• • [(10 mg) x Quantity (1 mL)]/Have (2 mg) = Amount wanted to give (5 mL) 

• • 10/2 = 5 mL needed to administer to the patient 

An example of the dimensional analysis method is using one or more conversion factors to obtain the desired amount. 

• A provider requests digoxin 0.75 mg IV daily be administered to a patient in the cardiac med-surg unit. Digoxin is available from the pharmacy at 0.25 mg/mL. How many mL will the nurse need to administer a 0.5 mg dose? 

• • (0.75 mg/ x mL) x (1 mL/0.25 mg) = desired mL 

• • 0.75/0.25 = 3 mL needed to administer to the patient  

Core Concepts of Drug Calculations: Research on Learning Methodologies on Medication Dosage 

Researchers have examined learning methodologies regarding medication dosage and have determined that there are several ways for future and current nurses to learn about medication dosages. While common approaches to drug calculations include ratio proportion, dimensional analysis, and the desired over-have method, several nurses in practice also rely on technology for drug calculations as well, especially in critical care situations.  

While technology can have many benefits, technology use is not a substitute for manual drug calculations and nursing judgment. Research has shown that nursing education programs need to focus on students’ mathematical skills, confidence in patient care, and understanding in pharmacology and provide several clinical and mathematical opportunities for students to practice their drug calculation skills (1,2,3,4).  

Nursing Considerations 

What Is the Nurses’ Role in Drug Calculations and Administration?  

Nurses remain the most trusted profession for a reason, and nurses are often pillars of patient care in several healthcare settings. Patients turn to nurses for guidance, education, and support. While there is no specific guideline for the nurses’ role in drug calculations in particular, here are some suggestions to provide quality care for patients and to ensure your competence in drug calculations (1,2,3,4).  

• Know where your medications are at all times. Oftentimes, with patient care, especially in hectic care settings, you can lose sight of your work computer, medications, syringes, and other supplies needed to administer a medication.  

• Be aware of your surroundings. Things can move very fast in health care, and medication errors are very common. If you notice that someone is talking to you when you are performing a drug calculation, consider asking them not to speak to you until you are finished with the drug calculation. If they are a fellow nurse or provider, they can also double-check your medication calculation as well.  

• Make sure you are familiar with the medications you are administering. Dosing is one thing, but there are several medications to be familiar with as well. Keep up to date with your pharmacological knowledge as much as possible to be aware of any red flags in dosage or administration.  

• Stay up to date on the latest training on dosing and medication administration from your organization and continuing nursing education if applicable.  

• Review the EHR with every patient for their allergies and health history. Charts can look similar, so make sure you are charting and documenting the correct patient when you are caring for them. Use your EHR’s dosing calculator if provided, but also confirm with your calculations as well since you are the one administering the medication.  

• Monitor the patient’s response to the medication, as this can help indicate if there was a medication dosing calculation error or if the medication is not providing its intended therapeutic effect.  

How can nurses identify if there is a possible error in a drug calculation?  

Unfortunately, it is not possible to look at the patient and notice an error in drug calculation immediately. Some medication errors might never show any visible clinical symptoms in the patient, whereas some other medication dosing errors can be fatal for the patient. It is important to monitor your patient’s health and see how they are responding to the medication.  

If you know you have made an error in drug calculation and administered the incorrect dose to the patient, monitor the patient, explain the situation to the patient, and then follow your workplace’s protocol on incident safety and reporting.  

What should patients know about drug calculations? 

Patients should know that anyone has the possibility of experiencing or performing a drug calculation error if medications are involved. Here are important tips for patient education regarding drug calculation errors in the inpatient or outpatient setting.  

• Tell the nurse of any side effects from any medications administered 

• Tell the nurse of any allergies, health history, or side effects from other medications  

• Ask the nurse if you should be aware of any specific side effects from the medication administered  

• Ask the nurse questions about the medication before administration, as patients have the right to know about the medications being administered  

• Try not to speak to the nurse when they are performing medication calculations to reduce the risk of medication dosing errors 

Conclusion 

Medication administration and drug calculations are here to stay for as long as health care and nurses exist. With the rise of more nurses using technology in their work, it is important to be aware of the use of drug calculations without technology and how to be mindful of drug calculation processes in the workplace. 

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