Prazosin (Oral)

Prescribed to patients with high blood pressure, Prazosin relaxes the patient’s blood vessels and enables blood to travel through them more easily.


High blood pressure, or hypertension, occurs when the pressure of the blood in the patient's arteries is consistently elevated. High blood pressure can be categorized into either primary or secondary hypertension, although primary hypertension is more common than the latter. When primary hypertension occurs, the patient's blood pressure is increased due to genetic and/or unknown lifestyle factors, whereas secondary hypertension occurs due to specific, identifiable factors. Some medications, for instance, may cause patients to develop secondary hypertension.

Although high blood pressure may not cause the patient to suffer symptoms at first, these may become apparent at a later stage. In some cases, patients report headaches, dizziness, lightheadedness, fainting and/or tinnitus when suffering from either primary or secondary hypertension.

Even if patients are not exhibiting any symptoms of high blood pressure, the condition can put them at risk of suffering other health complications. Hypertension tends to increase the risk of heart attacks, congestive heart failure and strokes, for example. In addition to this, very high blood pressure can constitute a medical emergency in itself and may cause organ damage in severe cases.

When patients have high blood pressure over a long period of time, the increased pressure on the arteries and the heart can result in them not working properly. When this happens, patients may be more likely to suffer internal damage and to experience a health crisis.

Whilst many patients are able to lower their blood pressure by making lifestyle and dietary changes, medications can also be used to reduce hypertension. Prazosin, for example, relaxes the blood vessels and allows blood to flow through them more easily. Due to this, patients with hypertension may be prescribed Prazosin on an on-going basis.

As well as reducing the patient's blood pressure in the short term, Prazosin can also have a positive impact on the patient's long term health. Once their blood pressure is returned to a normal range via the use of Prazosin, the patient's risk of suffering complications, such as heart attacks or strokes, should decrease as well. Based on this, Prazosin can be used to improve the symptoms of hypertension itself and to reduce the risk of the patient's experiencing further health complications.

Conditions Treated

Type Of Medicine

  • Antihypertensive

Side Effects

When patients take prescription medication, they should be told if any side-effects could occur as a result of their treatment. Although it's not uncommon for patients to experience adverse effects when taking medication, these can often be reduced or minimized with further treatment.

Often, the side-effects associated with Prazosin begin to wear off as patients get used to the medicine. The following adverse effects may not, therefore, require medical treatment:

  • Drowsiness
  • Nausea
  • Headache
  • Nervousness
  • Frequent urge to urinate
  • Dryness of the mouth
  • Lack of energy
  • Unusual weakness or tiredness

Although the side-effects listed above only tend to occur when patients first start taking Prazosin, patients should still seek medical help if they are concerned about the presence of any adverse effects. If they are severe or do not diminish over time, for example, patients should obtain medical advice.

When taking Prazosin, it is possible that patients may experience other side-effects as well. If patients exhibit any of the following adverse effects, they should seek medical help:

  • Lightheadedness or dizziness, especially when getting up from a sitting or lying position
  • Difficulty breathing
  • Pain in chest
  • Fainting (sudden)
  • Pounding heartbeat
  • Swelling of the lower legs or feet
  • Loss of bladder control
  • Painful or prolonged erection of the penis

In addition to this, patients should seek medical assistance if they experience any side-effects which are not listed here.


When patients are first prescribed Prazosin, they are usually given a dose of 1mg to be taken two or three times per day. Following this, their dose may be increased if their blood pressure remains elevated. Although it's not uncommon for patients to be given a higher dose of Prazosin, the maximum dose of this medication is normally 20mg per day.

If possible, patients should try and take their medication at the same time each day, unless their doctor has advised otherwise.

Although this is a standard dose of Prazosin, every patient will be assessed individually and may, therefore, be given alternative dosage instructions. Typically, physicians will take the patient's current blood pressure and medical history into account when prescribing Prazosin, as well as any other medications they are currently taking.

Unless patients are advised to stop taking Prazosin, they should continue to take their medicine as instructed, even if they begin to feel better. Patients may need to take medicine for hypertension on an on-going basis, even if they aren't displaying any symptoms of the condition.

Although Prazosin can be used to lower the patient's blood pressure and control hypertension, it does not cure the condition. In many cases, patients will be given instructions to change their lifestyle and diet, as well as being prescribed medication. If the patient is able to successfully change their lifestyle and modify their diet, their dose of Prazosin may be reduced over time. However, patients should not change their dose of medication themselves. Instead, their doctor will amend the dose of Prazosin, if it is necessary to do so.

If patients forget to take a dose of Prazosin, they should take it as soon as they remember to do so. However, if their next dose of medicine is due in the near future, they should skip the missed dose completely. It is not appropriate to take a double dose of Prazosin, even if an earlier dose has been missed.

Potential Drug Interactions

If patients are taking or using any other medicines, Prazosin could interact with them and cause unwanted effects. Due to this, Prazosin may not be prescribed alongside the following medicines:

  • Tadalafil
  • Asenapine

Although Prazosin is not generally prescribed in conjunction with the medicines listed above, doctors may deem it appropriate in some cases. If so, the patient's dose may be modified in order to reduce the chance of an interaction taking place.

If Prazosin is taken alongside any of the following medicines, it may increase the risk of side-effects occurring:

  • Acebutolol
  • Metipranolol
  • Alprenolol
  • Celiprolol
  • Atenolol
  • Levobunolol
  • Betaxolol
  • Esmolol
  • Bevantolol
  • Mepindolol
  • Bisoprolol
  • Carteolol
  • Bucindolol
  • Dilevalol
  • Carvedilol
  • Metoprolol
  • Timolol
  • Labetalol
  • Nadolol
  • Vardenafil
  • Nebivolol
  • Sildenafil
  • Propranolol
  • Tertatolol
  • Oxprenolol
  • Talinolol
  • Penbutolol
  • Sotalol
  • Pindolol

Whilst the above medicines may increase the risk of side-effects occurring, this doesn't mean that they won't be prescribed alongside Prazosin. Doctors may be able to provide specific advice to reduce the risk of the patient suffering certain adverse effects and, if necessary, they may prescribe additional medication to minimize side-effects.

Drug interactions may also occur between Prazosin and some over-the-counter medicines, supplements and/or vitamins. Patients should inform their doctor if they are using any of these substances before taking Prazosin and should seek medical advice before taking any other substances once they have started treatment for hypertension.


Before patients start taking medicine for high blood pressure, they will need to disclose their medical history to their physician. There are some conditions which may affect the suitability of Prazosin as a treatment. These include:

  • Heart disease
  • Angina
  • Kidney disease
  • Cataract surgery
  • Postural hypotension

When patients are taking Prazosin, they may feel lightheaded, dizzy or less alert than normal. Due to this, patients should not drive, operate heavy machinery or carry out tasks which require their full attention until they know how they respond to the medicine.

Feelings of dizziness and lightheadedness may occur if patients get up from a sitting or lying position suddenly. Patients may also be at risk of fainting if they get up from sitting or lying down too quickly. This may be more likely to occur when patients first start taking Prazosin or if their dose has been increased. The risk of fainting, dizziness and lightheadedness can be reduced if patients get up slowly.

Consuming alcohol can exacerbate feelings of lightheadedness and dizziness. Drinking alcohol may also increase the risk of the patient fainting. When taking Prazosin, patients should reduce their alcohol consumption or refrain from drinking alcohol at all.

Standing up for a long time, exercising and/or hot weather can also increase the risk of the patient fainting and feeling lightheaded or dizzy. Patients should, therefore, adapt their routine to ensure that they aren't exposed to hot environments for long periods of time and that they aren't required to stand for lengthy periods. Similarly, patients may need to refrain from intensive exercise until they are aware of how the medicine affects them.

If Prazosin is prescribed to patients who are pregnant, the risk to the unborn baby cannot be ruled out. Due to this, Prazosin is not normally prescribed to pregnant patients unless the benefits clearly outweigh any possible risks. If patients are pregnant, they should inform their doctor before taking Prazosin.

If patients become pregnant whilst taking Prazosin, they should seek immediate medical advice.

Although some medicines can be passed from the mother to infant via breastfeeding, it is not known if Prazosin can be transferred in this way. In addition to this, it is not known if Prazosin could cause harm to an infant if it is transferred via breastfeeding. Due to this, patients are normally advised not to breastfeed whilst taking this medicine. Patients should, however, seek medical advice if they are breastfeeding or are planning to breastfeed.

Prazosin can affect the results of some medical tests. Patients will need to inform medical practitioners that they are taking this medicine if they are due to undergo any tests or medical procedures.

A rare side-effect of Prazosin is a painful or prolonged erection. If patients suffer from this side-effect for four hours or more, they should seek urgent medical assistance. Without treatment, permanent and serious damage to the penis may occur.

Before patients begin taking Prazosin, they should notify their physician of any allergies they have. This includes allergies to medicines, foods, plastics, animals and dyes. In rare cases, patients may exhibit an allergic reaction when taking Prazosin. If so, they should obtain urgent medical help. A severe allergic reaction may involve the following symptoms:

  • Trouble breathing
  • Itching
  • Wheezing
  • Hives
  • Difficulty swallowing
  • Hoarseness
  • Swelling of the lips, mouth, tongue, throat and/or face


Unless otherwise advised, patients should store Prazosin at room temperature and in a location which is away from heat, moisture and direct light. It's also important that the medicine is kept in a closed container so that it does not deteriorate.

When keeping Prazosin, and other medicines, at home, patients should ensure that children and/or pets cannot access them. Using a locked cupboard or a lockable medicine box can help to keep medicines secure and family members safe, for example.

If patients are advised to stop taking Prazosin or if their medicine becomes out-of-date, patients will need to dispose of it. However, it is not safe to dispose of medicines with normal household waste. Instead, patients should contact their physician's office or pharmacist for advice. Often, doctors and pharmacists provide medical disposal services so that patients can dispose of medicines safely.


Even though numerous people have hypertension, they are not always symptomatic. This means that they may not realize that they're suffering from high blood pressure or that they have an increased risk of other health problems occurring. Although the patient may not be displaying signs of high blood pressure, this doesn't mean that their health isn't in jeopardy. Even when patients aren't outwardly suffering due to hypertension, their body can be sustaining internal harm.

Fortunately, hypertension can be treated and managed with medication, such as Prazosin. By relaxing the patient's blood vessels and enabling blood to flow around the body more easily, Prazosin can successfully reduce the patient's blood pressure. Furthermore, Prazosin can be used to manage hypertension on an on-going basis.

When taken regularly, Prazosin can ensure that the patient's blood pressure stays within a normal range and that their risk of suffering further health problems, such as strokes or heart failure, is reduced. Although Prazosin can be successful in treating hypertension when used in isolation, the patient's health may benefit if this medicine is used whilst the patient makes dietary and lifestyle changes as well.