Guanadrel (Oral)


When high blood pressure remains uncontrolled over a long period of time, some very severe problems can develop with arteries all over the body, and with the heart itself. Guanadrel helps to lower blood pressure by relaxing blood vessels, so as to facilitate the circulation of blood more easily, and to reduce the constriction which might be present. It controls specific nerve impulses along the pathways used by nerve signals to accomplish this relaxation effect.

Blood vessels that service the brain, kidneys, heart and other organs are all affected, and can be made much safer for circulating necessary blood to these areas. Without the kind of control that guanadrel can offer, the likelihood of heart attack and stroke rises significantly for a person who has a high blood pressure condition. While a healthy lifestyle and diet can improve on the blood pressure condition over time, the most immediate assistance can be provided by a medication like guanadrel, which can have a direct impact on the blood vessels that may have narrowed or become in some way constricted.

Condition Treated

  • High blood pressure

Type Of Medicine

  • Anti-hypertensive
  • Adrenergic blocker

Side Effects

Along with the beneficial effects that it may impart to a patient, guanadrel also has the potential to cause some unwanted side effects as well. Not every patient will experience every side effect, but some will experience relatively severe side effects from taking this medication, although a high level of severity is rare.

After taking this medication, you should monitor any effects that show up in the immediate aftermath, especially the first few times you take the medication. If anything happens that makes you feel comfortable, you should contact your doctor and be prepared to describe whatever side effects have shown up, as well as how severe you think they are. If severe side effects do occur, it may be necessary to consider an alternative form of medication, or possibly to reduce the dosage level that was originally prescribed.

While it is extremely rare, some people do develop an allergic reaction to guanadrel, and this is something that should be attended to immediately because of the potential for life-threatening side effects to develop. Symptoms to look for an allergic reaction include the following:

  • Swelling or puffiness around the facial area, especially in the eyelids, lips, tongue or throat
  • Extreme itchiness at various sites around the body
  • The sudden appearance of hives and rashes on skin surfaces
  • Dizziness or lightheadedness, with sensation that you may be about to faint
  • Difficulty with breathing, sometimes accompanied by a powerful sensation of tightness in the chest.

Some of the more common side effects of which patients taking guanadrel do experience are those listed below:

  • A relatively sudden gain or loss of weight
  • Unusual weakness or fatigue
  • Powerful drowsiness, lightheadedness, dizziness, or even fainting, often experienced after rising from a lying position
  • Unusual difficulty with ejaculating
  • Frequent nighttime urination
  • Muscle pains or soreness
  • Tremors or shaking
  • Dry mouth
  • Persistent diarrhea
  • Significant increase in bowel movements.

In addition to those side effects listed above, some other milder side effects may come and go in the early stages of a treatment program with guanadrel. These normally occur as the body is adjusting itself to a new medication, and rarely develop into anything serious enough to require medical attention, but will simply fade away of their own accord after a day or two.


Dosage of this medication will vary from patient to patient and will be prescribed by your doctor in accordance with several factors. These factors include the strength of the medication itself, the time duration between dosages, your body's tolerance to the medication and the specific medical condition which you may be suffering from.

It is important that you don't miss dosages of the medication, even though you may be feeling perfectly healthy. It's typical for many high blood pressure patients to feel normal almost all the time while the high blood pressure condition exists, and it's only when things reach a critical stage that a patient might feel significant issues.

When taking guanadrel, it's advisable to take it at the same time every day to help you remember your dosage schedule, and to allow your body to adjust to the medication on a regular schedule.

A standard dosage for an adult using the oral tablet form of guanadrel is 5 mg twice each day as an initial dosage. For a maintenance dosage, your doctor may increase the dosage to anywhere between 20 and 75 mg in a day, with those dosages being equally divided in as many as four separate dosages.

Children being treated with guanadrel have no standardized dosage schedule which is typically recommended. Since high blood pressure does not typically affect young people as frequently as adults, any pediatric cases are special in nature, and must be reviewed by the family doctor for any kind of dosing recommendations.

While taking medication at the same time every day should help you to remember to keep on schedule, there will always be times where you forget to take your medication. If this happens to you, it is permissible to take the missed dosage as soon as you remember it, unless you are nearing the time of the next regularly scheduled dosage. In that case, it's better to skip the dosage that you forgot about, and just wait for the next regularly scheduled dosage to get back on track. It's never a good idea to double up on dosages just to get back on schedule or because you feel that you need more medication.


As with almost all medications, there is a possibility that guanadrel may interact with other drugs or an existing medical condition that you already have. Neither of these types of interactions is desirable, and should be avoided if at all possible. In the case of interactions with other drugs, adverse side effects can be imparted to a patient who experiences this kind of drug interaction, and it's also possible for the effectiveness of either one of the drugs to be seriously diminished, and even rendered useless.

The medications that are most commonly checked for by doctors who are exploring the potential for drug interactions are the following:

  • Toloxatone
  • Selegiline
  • Rasagiline
  • Brofaromine
  • Furazolidone
  • Tranylcypromine
  • Yohimbine
  • Ipronlazid
  • Isocarboxazid
  • Clorgyline
  • Procarbazine
  • Lazabemide
  • Nialamide
  • Moclobemide
  • Linezolid
  • Pargyline
  • Phenelzine.

With regard to medical conditions that may be impacted by using guanadrel, the following situations may provide an opportunity for interaction. In order to avoid this kind of impact for you personally, you should have a consultation with your doctor about your medical history and any diseases or prior serious conditions you may have experienced. You should especially make your doctor aware of any of the medical conditions which appear on the list below:

  • Frequent fevers
  • Heart or blood vessel issues, including disease
  • Recent strokes or heart attacks
  • Any history of asthma or breathing difficulties
  • Chronic diarrhea
  • Stomach ulcers
  • Pheochromocytoma.


There are some important warnings or precautions that you should be aware of as a patient being treated with guanadrel. The first of these is that you should have regular, scheduled appointments with your doctor so that they can monitor the effectiveness of the medication and make sure that it is working to lower your high blood pressure.

You should be aware of the potential for dizziness or lightheadedness, which can occur when you rise up quickly from a sitting or lying position. In some cases, you may even faint when doing this quickly, especially in the morning hours. This makes it advisable for you to rise slowly when you have been laying down for a period of time or when you've been sitting for quite a while.

It will probably help for you to simply sit on the edge of your chair or bed for a minute to transition to an erect state before actually rising. If this condition persists or worsens, you should contact your doctor immediately and seek advice. This condition can also be made worse by drinking alcohol, since this can compound the disorientation that may be triggered by the drug itself. It is, therefore, not advisable to regularly drink alcohol while also taking guanadrel.

Similar reactions are possible when you have been out in the hot sun for a period of time, so it's best to avoid prolonged exposure to heat and humidity while taking this drug.

Do not begin taking other drugs without consulting your doctor first while you are being treated with guanadrel. This includes over the counter drugs, vitamins and herbal supplements, because there's a potential for any of these to interact with your high blood pressure medication in a way that you may not anticipate. Discuss any new drugs with your doctor so this can be avoided.

Before you have any kind of surgery, either on the body or dental surgery, make sure to alert your doctor or dentist to the fact that you are taking guanadrel. It may be necessary to discontinue your guanadrel medication temporarily while you are undergoing surgery, or it may be necessary to lower your dosage temporarily until after surgery has been accomplished.

If you should develop fevers after taking guanadrel, alert your doctor to this fact, since it may be necessary to reduce your dosage level in order to avoid the fevers. Make sure to tell your doctor if you have had any allergies in the past to substances such as foods, preservatives, pets or fabrics, because these can be re-triggered by active or inactive ingredients used in the manufacture of guanadrel.

It is more common for any of the side effects associated with this medication to have an effect on geriatric patients, because they have historically shown a greater susceptibility to those side effects than younger patients. It is also more likely for geriatric patients to be prescribed lower dosages of guanadrel, because trace amounts remain in the system longer for elderly patients than they do with younger patients. No studies have been conducted on pediatric patients being affected by this medication, so any impacts would have to be closely monitored and reviewed by your family doctor.

Women who are pregnant or thinking of becoming pregnant should always consult with their doctor about taking any new medication, including guanadrel. Animal studies that have been conducted have not revealed any harm to the fetus of a mother who has been given guanadrel, but it should be remembered that there have been no comparable human studies conducted in the same vein. While it is unlikely that guanadrel will have any kind of adverse effect on a nursing infant, breast-feeding is still something that should be consulted about with the family doctor, so that any risks can be considered before proceeding.


This medication should be stored out of the reach of pets and any small children who may be in the household. This involves keeping your medication out of weekly pill reminders, as these do not have proper locking mechanisms that can prevent access. The location in which guanadrel is stored should not be subject to extremes of heat, cold or humidity, and should also not experience direct lighting of any kind.

When this medication expires or goes unused for any reason, it should be disposed of according to guidelines provided by your doctor or pharmacist. If this information is unavailable, you can check the FDA website for the safe disposal of medicines.


Guanadrel is a medication belonging to the class of drugs known as anti-hypertensives, and its primary use is in the management of high blood pressure. While it cannot cure the condition, it does do a good job of controlling the factors that contribute to high blood pressure, especially the narrowing of blood vessels. By relaxing blood vessels, a wider flow can be achieved, and the pressure that would otherwise be present in blood circulation can be lessened considerably.