Guanabenz (Oral)

Guanabenz is an oral medication prescribed as part of a treatment plan for patients with high blood pressure. While it is effective in lowering blood pressure, it is not a cure for the condition on its own.


High blood pressure is a dangerous condition that forces the heart and arteries to work harder than they are designed to. Over time, it will damage the heart, arteries, blood vessels and other parts of the body if not brought under control.

Guanabenz takes control of certain nerve impulses in order to make blood vessels relax so blood can flow through them more easily. This helps to lower blood pressure in the body, and allows blood vessels, arteries, and the heart to work more like they were designed to in the first place.

While Guanabenz does help patients with high blood pressure to manage their condition, it is not a cure. In addition to taking medication, patients need to commit to making dietary and lifestyle changes in order to permanently keep their blood pressure down at lower levels. The kinds of changes patients need to make include switching to a low fat / low sodium diet, exercising regularly, not smoking, and only drinking alcohol in moderation.

Brand names for this medication include Wytensin

Conditions Treated

Type Of Medication

  • Antihypertensive

Side Effects

This medication, like many others, was made with the intention of helping to improve the health of the person taking it. Because no one person's medical condition is exactly the same as another person's, there are times when unintended adverse reactions (or side effects) occur. Some effects are less serious than others, and may or may not need medical attention. If you have any questions or concerns about the possible effects of guanabenz, you should talk to your doctor.

A few of the side effects that occur more often with guanabenz include:

Should any of the above side effects continue after guanabenz has taken full effect or worsen after taking it, talk to your doctor about ways to mitigate the negative effects or about adjusting your dosage, if necessary. Guanabenz typically starts working at full effect within two weeks, so talk to your doctor if these effects last for longer than that.

Other side effects are less common. If they occur, you should consult a healthcare professional. These effects could be an indication that something else is going on that needs to be treated. They include:

  • Fainting

Rarely, some of the inactive ingredients in guanabenz have been known to cause a severe allergic reaction. Seek immediate medical attention if you experience any of the following symptoms after taking a dose.

If too much of this medication is taken at one time, a person can experience an overdose. Most cases of guanabenz overdoses are in children who have somehow gotten a hold of the medication accidentally. Check for the symptoms listed below and contact the nearest poison control center or seek medical attention, depending on the symptoms and how they seem to be progressing.

Symptoms of an overdose include:

  • Slow breathing or difficult breathing


Exact dosage information and instructions for taking guanabenz may vary, depending on what your doctor believes will be most effective for you and your condition. Specific dosages and instructions for taking them are often determined by the medical condition this drug is being prescribed for, other medicines and supplements the patient might be taking at the time, and other medical conditions the patient has.

Drug manufacturers usually include recommended instructions for taking their medication that are based on their knowledge of the condition and the drug's intended effect, but it is up to the doctor prescribing it to decide more precisely the best dosage for their patient.

The manufacturer recommends that an adult taking guanabenz for treatment of high blood pressure should initially take 4 mg by mouth twice a day at evenly spaces intervals. After the initial dosage, take 4-8 mg orally twice a day, with the potential for gradual increases of 4-8mg as necessary up to a maximum of 32 mg per day. Any increase in dosage should be determined by the doctor prescribing the medication.

The effects of guanabenz on patients under the age of 18 have not been determined, so you should only administer to your child as directed by their doctor.

If you miss any doses of guanabenz, you should take the missed dose as soon as you realize you missed it, unless it is almost time to take the next dose. In that situation, skip the missed dose and take the next one at the time you would normally take it. Do not double up on doses.

As with all medications, follow the doctor's directions when taking this medication. While there are general recommendations from the manufacturer as far as taking it, your doctor's instructions are based on their knowledge of you and your specific medical condition. Do not take any more of this medication than directed, and do not take any less. Do not double up on doses. Do not take any more than the maximum 32 mg of guanabenz in a day.

Types of Interactions

Under ideal circumstances, guanabenz helps to lower blood pressure for patients experiencing hypertension. When that patient is undergoing treatment for other medical conditions, they often are on other medications that can change guanabenz's intended effects. Even if the only thing the patient is taking is a health supplement, some supplements can similarly change the effects of the medication they are taking. Sometimes the effects can be helpful. More often, the effects of these other drugs and supplements can decrease the effectiveness of guanabenz or even cause additional medical issues.

Drug Interactions:
The list of drugs, both prescribed and over-the-counter, and supplements that are known to interact with guanabenz include:

  • Anti-diabetic medications like metformin

Please note that the drugs and supplements stated above are not all of the drug and supplements guanabenz can have negative interactions with. Your doctor will have a more complete list and specific information about how any medications or supplements you are taking interact with guanabenz.

Food and Drink Interactions:

Alcohol is known to increase guanabenz's blood pressure lowering effects, so use caution when you are drinking so that your blood pressure does not drop to dangerous levels. Caffeine is known to raise blood pressure, so be cautious about consuming caffeinated beverages while on this medication so that guanabenz can work as intended.

Medical Interactions:

Besides the possible interactions with other medications and food, and drink, there are several medical conditions that could interact negatively with guanabenz. The list of these conditions includes:

  • Bradyarrhythmia / bradycardia (heart rate that is slower than expected)

If you have any of these medical conditions, you should consult with your doctor so they can adjust your dosage or find alternative treatment methods for you if necessary. Dosages of guanabenz that are too high can negatively affect people with these conditions.


Do not drive, use machinery, or perform any other tasks that might be considered dangerous until you know what effect guanabenz will have on you. This medication can cause you to feel drowsy, dizzy, or otherwise much less alert than you need to be in order to perform these specific kinds of tasks.

Guanabenz can have a heightened effect in the elderly.

Before undergoing surgery (medical or dental) or emergency medical treatment, tell the doctor or dentist in charge that you are taking guanabenz.

Do not take other medications (prescribed or over the counter) at the same time as guanabenz unless you have discussed using them with your doctor.

Tell your doctor if you are allergic to guanabenz or any other medication.

Let your doctor know if you have coronary artery disease, liver or kidney disease, or if you have recently suffered a heart attack.

Check in with your doctor before you stop taking guanabenz. There is a risk of your blood pressure bouncing back too high if you stop taking it at one, and your doctor may want to wean you off of it gradually.

Talk to your doctor about the use of guanabenz if you are pregnant or planning to become pregnant. If you are pregnant, there is an increased risk of fetal abnormalities, fetal loss, and neonatal mortality. Your doctor should only prescribe it to you if the benefits of taking it outweigh the risks.

Be cautious about using guanabenz if you are nursing. While there is no data on the exact risk of excreting it into human milk, there is still potential for something to happen. The manufacturer recommends a discussion with your doctor about the risks before taking it.

Storage And Disposal Instructions

Store guanabenz in a tightly sealed container in an area that stays at or around room temperature (between 60 and 86 degrees Fahrenheit or 15 and 20 degrees Celsius). Also make it is not accessible to children or pets.

Keep the medicine away from sources of heat, like an oven or stove in the kitchen, or a space heater in other rooms. Also keep it away from sources of moisture, like a sink or shower in the bathroom.

Do not leave this medication sitting in a spot that is in the direct path of sunlight coming into your home. Places like a windowsill or countertops underneath windows receive direct sunlight, and should be avoided as storage areas for medication.

Guanabenz should not be kept cold. Do not store in places like the refrigerator, freezer, or rooms in your home that are difficult to keep at or around room temperature.

Do not hold onto expired or extra doses of guanabenz. You should dispose of the medication once it has expired or your doctor deems your course of treatment to be complete. If you have questions about how to dispose of the medicine, ask your doctor or pharmacist to instruct you on the proper methods of disposing of this medication.

Do not flush extra or expired medication down the toilet or pour it down a sink drain.


Guanabenz is a blood pressure medication that is used as part of an overall treatment plan for patients with high blood pressure. It allows the heart and blood vessels to work slower and more normally, which in turn prevents damage and future life-threatening conditions like heart attacks, stroke, and kidney disease. While this medication can be hugely beneficial to the process of treating high blood pressure, there are a number of risks involved with taking it that can only be ascertained by a doctor with full knowledge of a patient's medical history.

This is why it is imperative for patients to have open and honest lines of communications open with their doctor, and for them to be willing to disclose the entirety of their medical history. The list of medications that guanabana can interact with in a negative fashion is long, and there are dietary choices as well as medication conditions that can negate the use of the medication as well. A doctor with an intimate knowledge of their patient's condition can anticipate these challenges, and help their patient create a plan that effectively manages it.

When taken under the correct guidance, guanabenz effectively treats high blood pressure and allows patients to have a much longer and better quality life to enjoy with the people that they love around htem.


  • MedlinePlus:
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