Tenex (guanfacine)


When Is It Prescribed?

Tenex (guanfacine) is prescribed to treat:

  • Mild to Moderate High Blood Pressure or High Blood Pressure caused by kidney problems
  • Attention-Deficit Hyperactivity Disorder (NOT an FDA-approved indication but generally well accepted)

Tenex (guanfacine) is an alternative to stimulants for treating ADHD. It seems to work best in decreasing hyperactivity, but does not always improve distractibility (as stimulants do). Some physicians have found benefits in using this medication with children who have ADHD and conduct problems.

When Will It Start to Work?

This medication should be taken for at least four to six weeks to determine the therapeutic effects on lowering high blood pressure and other indications. Tenex (guanfacine) may not show peak beneficial effects until 12 weeks. It may take longer to feel the full therapeutic effects of Catapres due to indication, dosage, and other factors.

Are There Any Drug Interactions?

Always follow your physician's recommendations on how to take your medication. Even if you are taking one of the following substances, continue taking your medication as prescribed and consult your physician. Also, if you are taking any other prescription medications, herbal remedies, vitamins, and/or over-the-counter medications, be sure to tell your physician. There is more information available on drug interactions.

Pregnancy and Breastfeeding Issues

If you are pregnant, plan to become pregnant, or breastfeeding, discuss the potential risks of this or any medication with your doctor.

Other Important Information and Precautions

Tenex (guanfacine) is also used to treat heroin withdrawal, useful in problem pregnancies, and may help in treating some sleep disorders.

Hot environments, fever, and heavy exercise can cause fluctuations in blood pressure. Ask your physician for guidance in these instances.

DO NOT stop this medication suddenly; serious withdrawal symptoms can occur.

In addition to the information listed above, there may be other important issues or precautions related to this medication. For further information, you can ask your prescribing doctor or therapist.

Side-Effect Information

Only some people will experience side-effects--and no one experiences side effects in exactly the same way. If you experience any side effects, contact your doctor or clinician right away and continue taking your medication. The following list may not contain all of the side effects associated with this medication:

Most Common Side-Effectsdrowsiness, dry mouth, constipation, mild lowering of blood pressure on standing (orthostatic hypotension)
Infrequent Side-Effectsskin problems (skin rash, itching), headache, dizziness, fatigue, insomnia, indigestion, nausea, diarrhea, slow heartbeat
Rare Side-Effects/Risksamnesia, liver toxicity, edema or leg cramp, "rebound" high blood pressure (if stopped abruptly), sexual problems (decreased libido, impotence)

Most common side-effects

Some people report feelings of drowsiness throughout the day. If drowsiness is a problem for you, talk to your doctor about it. He or she may change your dose or tell you to take the medication at night. In the meantime, be sure not to drive a car or operate other heavy machinery while you are feeling drowsy.

Dry mouth
Some people taking your medications experience dry mouth. Although dry mouth may not go away completely, it usually gets better with time. Dry mouth can be relieved by sucking on hard candy or crushed ice, drinking plenty of fluids, or eating frozen grapes.

Hypotension is abnormally low blood pressure. Temporary hypotension may result in a simple faint. Certain medications should be used with particular caution in people with known cardiovascular disease, cerebrovascular disease, or conditions associated with hypotension.

Infrequent side-effects

Skin problems
Some people taking your medication may develop an allergic reaction in the form of a rash, hives or itchiness.

Your medication can cause headaches, which often fade as your body adjusts to the medication. If you experience headaches, and they're disruptive, talk to your doctor before you take any pain medications. He or she can let you know which medications are safe to take with your medications.

If you feel dizzy when you sit or stand up quickly, there are some precautions that you can take to avoid injury. Get up very slowly from a laying or sitting position and make sure you have something to hold onto as you get up. Then, wait a moment or two before you start walking.

When you begin taking your medication, you may experience fatigue. Fatigue is mental or physical tiredness. If this symptom becomes bothersome, consult your doctor for additional information.

If you experience insomnia as a result of your medication, your doctor may change your dose, prescribe a medicine to help you sleep, advise you to take the medication in the morning, or change your medication altogether. To combat insomnia, avoid eating heavy meals, exercising, or drinking caffeinated beverages before bed.

Some people taking your medication may experience indigestion. Indigestion is usually seen when the medication is first taken, and will improve without specific treatment. Ask a physician about which over-the-counter drugs are safe to take with this medication.

Most people who experience this side effect notice that it disappears in a few weeks. To reduce or eliminate nausea, eat several small meals per day instead of three big ones, or try snacking on dry toast or crackers.


Loose and/or frequent bowel movements distinguish this side effect. Severe or prolonged diarrhea can cause a loss of needed fluid and nutrients. There are over-the-counter medications to counteract diarrhea, however; check with your doctor to see what can be done about this side effect.

Slow Heartbeat

Some medication can cause one's heart rate to slow down. Usually, this is not a serious side effect but contact your doctor if it persists or you are worried about it.

Rare side-effects/Risks

A rare side effect, amnesia, which is characterized by a total or partial loss of memory, can occur when taking this medication. Consult your doctor immediately if this side effect occurs.

Liver irritation
The symptoms of liver irritation include extreme tiredness, severe nausea, and yellowing of the whites of the eyes and skin. Contact your doctor right away if you experience any of these symptoms!

Peripheral Edema
Swelling of the feet can be caused by your medication. The swelling is minor if your shoes feel tight but it is severe if you are not able to get your shoes on and your feet hurt. Notify your doctor if you are experiencing peripheral edema. To help reduce swelling:

  • If you are going to be sitting for some time, sit with your legs elevated
  • Do not stand for long periods of time
  • Move your legs often, working muscles in your legs will help keep the fluid to a minimum

High Blood Pressure (hypertension)

High blood pressure, or hypertension, can be caused, among other reasons, by certain medications. This side effect may disappear over time or may cease when medication is stopped. Consult your physician about what steps to take if you experience the following side effect.

Sexual difficulties
Changes in sexual function may include difficulty achieving orgasm, difficulty maintaining an erection, delayed ejaculation, or decreased physical sensation. These problems are sometimes the most difficult for people to discuss. They might feel embarrassed and instead of mentioning it to their physicians, they suffer with it or worse yet, stop their medication on their own. Doctors are accustomed to talking about these problems and they are trying to help you recover. Please do not hesitate to talk to your doctor if you experience this or any other side effect or risk.

Side-effects and risks other than those listed above may also occur. Talk to your prescribing doctor or therapist about any potential or existing side-effects that you’re concerned about.

Every effort has been made to ensure that the information provided by 4therapy.com is accurate and up-to-date, but no guarantee is made to that effect.

4therapy.com’s medication information is a reference resource designed as a supplement to, and not a substitute for, the expertise, skill, knowledge, and judgment of healthcare practitioners in patient care. 4therapy.com does not assume any responsibility for any aspect of healthcare administered with the aid of information 4therapy.com provides.