August 11, 2023

Welcome to this week’s Pharmacy Phriday. In a recent installment we reviewed Labetalol and its use in the correction of blood pressure associated with OB emergencies. At that time, it was stressed that there are two beta blockers found in our UH drug boxes and the need for the provider to be careful to not confuse these two “sound-alike” medications. This week’s focus of our column will be on the medication Metoprolol.  

Though they are both beta blockers, they are also very different drugs. The difference in how the two medications work is that Metoprolol is a “selective” beta blocker and Labetalol is a “non- selective” beta blocker. In the case of Metoprolol, the receptors affected are primarily cardiac sites which result in decreased cardiac output.

Metoprolol is a very common medication used and prescribed for patients diagnosed with high blood pressure, arrythmias, heart failure, following an AMI, and other various conditions. It is classified as class II antiarrhythmic. The medication is cardio selective, blocking primarily beta 1 receptors in the cardiac tissue, slowing rate, reducing the strength of cardiac contractions, and thus lowering the blood pressure.  

Although widely used, metoprolol can still be a dangerous drug. Some of its most common side effects include tiredness, dizziness, itching, and rash, but serious side effects can include bradycardia, hypotension, CHF, and heart blocks. Beta blocking effects of metoprolol occasionally exacerbate asthma, other reactive airway diseases, and allergic reactions. Due to some of these various concerns, Metoprolol is a “red boxed” medication and requires on-line medical direction prior to administration.

UH protocol directs the paramedic level provider to consider and seek approval for Metoprolol’s use in cases of stable, narrow complex tachycardias (A-fib and possibly SVT) to control the ventricular rate following the consideration and/or use of other treatments or concerns. Metoprolol should also be considered in cases of recurrent SVT.  

It is important to remember that not all tachycardias require treatment. If the patient is stable and asymptomatic, all that may be required is supportive care. In some cases, the tachycardia may be beneficial for the patient as a compensatory response of the body to conditions such as fever, dehydration, etc. Other treatment options prior to the use of Metoprolol may include, depending on the regularity of the complexes, use of vagal maneuvers, Adenosine, or fluid boluses (see UH’s “Narrow Complex Tachycardia” algorithm).

When indicated, dosing for Metoprolol is 5 mg IV/IO given over one minute. The provider should be sure to monitor the heart rate, ECG, capnography, respiratory status, and blood pressure during administration watching for adverse side effects as mentioned above. The provider can expect to see an almost immediate effect of the drug and should cease administration if any adverse effects are noted. Two doses are provided in the UH drug boxes. Some texts recommend a second dose in two minutes if vitals remain stable, but again, under UH protocol, only after approval by medical direction.  

Contraindications to the use of Metoprolol include many of the same significant side effects mentioned above, including Asthma, CHF, heart blocks, bradycardia, hypotension, or shock of any type. Metoprolol is a class C medication in the pregnancy class and is recommended only if the benefits to the mother outweigh the fetal risks. Another contraindication includes cases of a cocaine induced MI due to the possibility of elevations in blood pressure from unopposed alpha stimulation. Prehospital use of Metoprolol is not indicated for use in the pediatric patient.

Sincerely,



The UH EMS-I Team

University Hospitals

August 8, 2022

Dear Colleagues,

Welcome to this week’s Pharmacy Phriday. In our last installment, the importance of the 6 rights of medication administration was reviewed, including the ‘right medication”. Two similar-sounding medications in the UH drug box that may confuse the provider if not careful include Metoprolol and Labetalol, both beta blockers but very different drugs.  This week’s focus of our column will be on the medication Metoprolol.

Metoprolol is a very common medication used and prescribed for patients diagnosed with high blood pressure, arrhythmias, heart failure following an AMI, and other various conditions.  It was, in fact, the fifth most prescribed medication to patients according to a drug stats database in 2019, so EMS will find the medication on many patient lists.  

Metoprolol is considered a class II antiarrhythmic and listed as a “selective” beta blocker.  The medication is cardioselective, blocking primarily beta 1 receptors in the cardiac tissue, slowing rate, reducing the strength of cardiac contractions, and thus lowering the blood pressure.  In higher doses, higher than used in the prehospital setting or within the UH protocols, the “selectivity” to only beta 1 receptors is decreased. 

Although widely used, metoprolol can still be a dangerous drug. Some of the most common side effects include tiredness, dizziness, itching, and rash, but serious side effects can include bradycardia, hypotension, CHF, and heart blocks. Beta-blocking effects of Metoprolol occasionally exacerbate asthma, other reactive airway diseases, and allergic reactions. Due to some of these various concerns, Metoprolol is a “red boxed” medication and requires online medical direction prior to administration.

UH protocol directs the paramedic level provider to consider and seek approval for Metoprolol’s use in cases of stable, narrow complex tachycardias (A-fib and possibly SVT) to control the ventricular rate following the consideration of other treatments or concerns. Metoprolol should also be considered in cases of recurrent SVT. 

It is important to remember that not all tachycardias require treatment.  If the patient is stable and asymptomatic, all that may be required is supportive care.  In some cases, tachycardia may be beneficial for the patient as a compensatory response of the body to conditions such as fever, dehydration, etc. Other treatment options prior to using Metoprolol may include, depending on the regularity of the complexes, use of vagal maneuvers, Adenosine, or fluid boluses (see UH’s “Narrow Complex Tachycardia” algorithm). 

When indicated, the dosing for Metoprolol is 5 mg IV/IO given over one minute.  The provider should monitor the heart rate, ECG, capnography and respiratory status, and blood pressure during administration, watching for adverse side effects as mentioned above.  The provider can expect to see an almost immediate effect of the drug and should cease administration if any adverse effects are noted.  Two doses are provided in the UH drug boxes.  Some texts recommend a second dose in two minutes if vitals remain stable, but again, under the UH protocol, only after approval by medical direction. 

Contraindications to the use of Metoprolol include many of the same significant side effects mentioned above, including asthma, CHF, heart blocks, bradycardia, hypotension, or shock of any type. Metoprolol is a class C medication in the pregnancy class and is recommended only if the benefits to the mother outweigh the fetal risks.  Another contraindication includes cases of a cocaine-induced MI due to the possibility of elevations in blood pressure from unopposed alpha stimulation. Prehospital use of Metoprolol is not indicated for use in the pediatric patient.

In our next installment of Pharmacy Phriday, we will focus on Labetalol, a “non-selective” beta blocker, and discuss the differences between these two medications.  Till then, stay safe!

Sincerely,

The UH EMS-I Team

University Hospitals