Search for articles or Rx savings
Key takeaways
Propranolol is a beta blocker drug used to treat hypertension, arrhythmia, tremors, and sometimes anxiety or migraines.
It’s possible to overdose on propranolol, particularly if someone has not followed the dosage instructions.
Propranolol overdose symptoms include low blood pressure, low heart rate, weak heart contractions, fatigue, cough, lightheadedness, blurred or double vision, difficulty breathing, and fainting.
Treatment for propranolol overdose may include attempts to absorb the substance with activated charcoal, stomach pumping, and medications like glucagon.
Propranolol is a generic medication that’s in a class of medications called beta blockers. It’s available under the brand name Inderal and is typically prescribed to treat high blood pressure, heart disease, and essential tremor. It’s also approved to prevent migraine headaches. Although it’s effective for various health conditions, it can also cause serious issues when it’s not taken as instructed.
Can you overdose on propranolol?
Yes, it’s possible to overdose on propranolol. A plasma concentration higher than 2 micrograms per milliliter (μg/mL) is considered toxic, and concentrations higher than 3 μg/mL are fatal. Overdose is not particularly common, but still possible when propranolol is taken in ways other than how it’s prescribed.
How beta blocker overdose happens
Propranolol is a beta blocker, a class of medications that work by preventing beta receptors from being stimulated by the stress hormones epinephrine and noradrenaline. As a result, the stress hormones are limited in increasing blood pressure and heart rate. But ingesting too much can cause serious consequences. The following are some ways that a beta blocker overdose from drugs like propranolol could occur.
Not taking it as prescribed
Many times, beta blocker self-poisoning is accidental, a result of failing to follow the healthcare provider and pharmacist’s instructions. “As propranolol is often dosed two to three times a day, it can be hard to keep track of and remember whether one already took their dose or not. It happens to the best of us! This however can result in patients accidentally doubling up on a dose that had already been taken,” says Cooper Stone, DO, a psychiatrist in Philadelphia, Pennsylvania. “Similarly, it can be difficult to take one’s medications perfectly timed evenly throughout the day. Therefore sometimes doses may be less spaced than otherwise advised.”
Although someone who forgets a dose might also try to take two doses to make up for it, this can be dangerous since it means ingesting twice as much as necessary. If you forget to take a dose of propranolol or another beta blocker, simply take the next dose at the normal time instead.
“The risk of toxicity will depend in large part on the dose that is being prescribed and how well acclimated the patient is to the medication,” Dr. Stone says. “Accidentally doubling up on two 10 mg pills is less worrisome than doing the same for two 80 mg pills.”
Drug interactions
Propranolol may also interact with certain drugs, making overdose or serious side effects more likely. Dr. Stone says that accidental overdose can occur if a patient starts taking a medication that significantly reduces the metabolism of propranolol—particularly if the dose of propranolol they were taking was already high.
Some medication classes that can increase the level or effect of propranolol include:
- Antiarrhythmics
- Antihypertensive drugs
- Antidepressants
- Certain antibiotics, antifungals, and antivirals
- Migraine drugs
- Theophylline
- Warfarin
- Alcohol
Not all of these interactions will cause severe symptoms. But some could put you at greater risk of complications. Other interactions can make propranolol less effective. Let your healthcare provider know about all prescription and over-the-counter (OTC) medications you take, including vitamins, herbal products, and supplements.
Misreading labels
Every prescription drug’s label contains important information on how to take it. Always know the dosage of each pill, how often to take it, and what time of day to take it. This is especially important for anyone who is using propranolol tablets together with other medications that affect the heart—like calcium channel blockers or tricyclic antidepressants—since they may increase the risk of serious side effects.
Diet
While it’s not necessarily a serious overdose risk factor, diet can also influence how someone responds to a drug. For example, Dr. Stone says high-protein meals can increase the medication’s absorption. “This can be an issue if one is on a higher dose and normally takes this medication consistently without food but then decides to take it with a meal,” he says. “This is not to say you should not take propranolol with food; rather, one should just be consistent with taking it with or without food.”
Propranolol overdose symptoms
Recognizing the symptoms of propranolol overdose is important, so you know when to seek immediate treatment. Symptoms include:
- Lightheadedness
- Low blood pressure, which could lead to shock if too low
- Irregular, fast, or slow heartbeat
- Shortness of breath and swelling of the legs, indicating heart failure
- Trouble breathing
- Double or blurred vision
- Weakness
- Nervousness
- Excessive sweating
- Drowsiness
- Confusion
- Seizures
- Fever
- Coma
“Propranolol is a lipophilic beta blocker, which may easily cross the blood-brain barrier and may cause seizures in overdose situations,” according to Randy Gould, MD, a cardiologist at Manhattan Cardiology and contributor to www.labfinder.com. Other symptoms of propranolol poisoning may include weakness, fatigue, cough, lightheadedness, blurred or double vision, difficulty breathing, fainting, or even cardiac arrest.
Propranolol overdose treatment
At the hospital emergency department, doctors have a couple of different ways of treating beta blocker poisoning. “Treatment of propranolol overdose is primarily supportive and includes measures to accelerate the removal of the drug (e.g., gastric lavage, activated charcoal, and magnesium citrate), as well as treatment to reverse the drug’s severe hemodynamic effects,” Dr. Gould says.
Essentially, the doctors want to get the propranolol out of the person’s system as quickly as possible and get the cardiovascular system functioning normally again. Activated charcoal, for example, binds to substances in the stomach so they can’t enter the rest of the body. And gastric lavage—commonly known as stomach pumping—physically removes the drug from the body through a tube.
Clinicians may also administer certain emergency medicines. According to Dr. Gould, “epinephrine, atropine, isoproterenol, dopamine, and glucagon have all been recommended as therapeutic interventions.” Glucagon, for example, is a hormone that regulates blood sugar, and also increases the heart rate and blood pressure—so it may work against the low blood pressure and slow heart rate caused by beta blocker toxicity. Isoproterenol is used for a variety of heart conditions and can increase the heart’s strength in contractions.
In fact, a 2019 study on 2,967 cases of beta blocker toxicity showed that treatments like activated charcoal, gastric lavage, temporary pacemakers, glucagon, intubation for respiratory insufficiency, and cardiopulmonary resuscitation prevented a fatality in every case.
Additionally, an older case report from The American Journal of Medicine showed that high-dose glucagon and isoproterenol treatment can work for severe propranolol overdose. And, a 2022 case report from Clinical Medicine Insights concluded that healthcare providers should administer glucagon right away for overdose patients who are resistant to standard therapy.
Regardless, it’s important to get someone who might be overdosing medical help as soon as possible, so healthcare professionals can determine the best course of action.
If you think someone is overdosing
If you think someone is overdosing, call 911 immediately. It will help if you have an idea of the weight and age of the person who is overdosing as well as an idea of when the person last took the medication and how much they took. Try to keep them awake if possible, lay them on their side, and wait for paramedics to arrive. In these situations, don’t call poison control or search the internet, since it’s crucial to get the person immediate help.
Sources
- Inderal® (propranolol hydrochloride) tablets, Wyeth Pharmaceuticals, Inc. (2010)
- The many roles of beta blockers, Harvard Health Publishing (2024)
- Beta blockers overdose, Mount Sinai (2023)
- Activated charcoal: An effective treatment for poisonings, Poison Control
- Glucagon, Cleveland Clinic
- Clinical toxicology of beta blocker overdose in adults, Basic & Clinical Pharmacology & Toxicology (2019)
- Massive propranolol overdose. Successful treatment with high-dose isoproterenol and glucagon, The American Journal of Medicine (1986)
- Seizures and irreversible cardiogenic shock following propranolol poisoning: Report of 2 cases and literature review, Clinical Medicine Insights: Case Reports (2022)