Poisoning Due to Antihypertensives (Blood Pressure Medicine Overdose)

What to do right now

1. If the person is unconscious, not breathing normally, having a seizure or has collapsed, call 911 or your local emergency number. Start CPR if they are not breathing and you are trained.
2. If they are awake, call Poison Help at 1-800-222-1222 in the US (or your local poison center). It is free and available 24 hours a day. They will tell you whether the person needs the emergency department.
3. Keep the medicine packaging and note the drug name, strength, whether it is extended-release (ER, XL, SR, CD, LA), how many tablets may have been taken and when.
4. Keep the person lying down if they feel faint, and do not let them stand up quickly or drive.
5. Do not make them vomit, and do not give food, drink or other medicines unless advised.

How different blood pressure medicines cause harm

Symptoms of antihypertensive poisoning

• Dizziness, lightheadedness and low blood pressure, especially on standing
• Fainting or collapse
• A slow, weak or irregular pulse (see bradycardia)
• Cold, clammy, pale skin
• Nausea and vomiting
• Confusion, drowsiness or reduced consciousness
• Shortness of breath from fluid in the lungs
• Low urine output
• In children: floppiness, drowsiness, slow breathing and low blood sugar

Severe poisoning leads to cardiogenic shock, where the heart cannot pump enough blood to the organs, and can cause cardiac arrest.

Who is at risk

• Young children who find tablets in handbags, pill organizers or on the floor. A single tablet of a calcium channel blocker, beta blocker or clonidine can be enough to poison a toddler.
• Older adults taking several medicines, especially after a dose change or with dementia.
• People who take an overdose on purpose, often together with other medicines. See drug overdose.
• People with kidney or liver disease, in whom medicine builds up.
• People combining medicines that both lower blood pressure, or with alcohol.

How it is diagnosed

Doctors base the diagnosis on the history, the packaging and the examination. Tests include:

• ECG and continuous heart monitoring for slow rhythms and heart block
• Blood pressure monitoring, often with a line in an artery in severe cases
• Blood glucose: high in calcium channel blocker poisoning and sometimes low (hypoglycemia) in beta blocker poisoning
• Electrolytes and kidney function, including potassium, which can rise dangerously (hyperkalemia) with ACE inhibitors and ARBs
• Lactate, a marker of poor blood flow to tissues
• Acetaminophen and aspirin levels, because people who overdose often take several medicines
• Echocardiogram to see how well the heart is pumping

Hospital treatment

Treatment depends on the drug and severity:

• Activated charcoal may be given if the person is awake and arrives soon after the overdose.
• Whole bowel irrigation with a special solution may be used for large overdoses of extended-release tablets.
• IV fluids for low blood pressure.
• Atropine for a slow heart rate, though it often works poorly in these poisonings.
• IV calcium for calcium channel blocker poisoning.
• Glucagon for beta blocker poisoning.
• High-dose insulin with glucose (hyperinsulinemia-euglycemia therapy), which helps the poisoned heart use energy and is a key treatment for severe calcium channel blocker and beta blocker poisoning.
• Vasopressors such as norepinephrine to raise blood pressure.
• Pacing with an external or temporary pacemaker for very slow heart rates.
• Lipid emulsion therapy and ECMO (heart-lung bypass) in the most severe cases.
• Naloxone is sometimes tried in clonidine poisoning, with variable results.
• Dialysis for some drugs, such as atenolol, and for kidney failure.

People with no symptoms after an immediate-release overdose are usually observed for at least 6 hours. Those with extended-release products are often observed for up to 24 hours.

Complications and outlook

Most people with mild poisoning recover completely within a day or two. Severe calcium channel blocker or beta blocker poisoning can cause kidney injury, bowel damage, brain injury from low blood flow, and death, but survival has improved with high-dose insulin and other modern treatments. Early treatment is the most important factor.

Prevention

• Store all medicines locked up, out of children's sight and reach, including visitors' bags.
• Use child-resistant packaging, and never call medicine "candy".
• Fold used clonidine patches sticky side in and dispose of them safely.
• Use a pill organizer or blister packs, and keep an up-to-date medicine list.
• Ask your pharmacist to review all your medicines once a year.
• If you miss a dose, do not double up unless your doctor or pharmacist says to.

Frequently asked questions

What happens if you take too much blood pressure medicine?

Taking too much can lower your blood pressure and heart rate too far, causing dizziness, fainting, confusion, cold clammy skin and, in severe cases, shock and cardiac arrest. The effects depend on the drug and dose. Call Poison Help at 1-800-222-1222 in the US, or 911 if there are serious symptoms.

I accidentally took my blood pressure pill twice. What should I do?

Call Poison Help at 1-800-222-1222 (US) or your pharmacist for advice. A single extra dose of many medicines causes only mild dizziness, but some drugs are more dangerous. Sit or lie down, avoid driving, and get emergency help if you faint, feel very unwell or have a very slow pulse.

Which blood pressure medicines are most dangerous in overdose?

Calcium channel blockers such as verapamil, diltiazem and amlodipine, beta blockers such as propranolol, and clonidine are the most dangerous. ACE inhibitors, ARBs and diuretics usually cause milder poisoning. Extended-release forms can cause delayed, prolonged effects.

Can one blood pressure pill hurt a child?

Yes. For a toddler, a single tablet of a calcium channel blocker, beta blocker or clonidine can cause dangerously low blood pressure, slow heart rate, drowsiness or low blood sugar. If a child may have swallowed any blood pressure medicine, call Poison Help or 911 immediately, even if they seem fine.