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BP “Spikes” may occur due to emotional stress, a change in your medical condition, or when we are changing you from one long-acting BP drug to another.  When this occurs, if we give you an extra dose of your long-acting drug, it won’t act quickly to address the BP spike, and then it might act too well over the next 24 hours, dropping your BP excessively.

In this situation we can use Clonidine to “cover” BP spikes.  Clonidine is a centrally acting BP medication; in other words it does not act directly on the heart or the arteries.  Clonidine blocks one the adrenaline receptors (alpha 2) in the brain, such that any “over activity” of the nervous system’s message to the arteries to constrict and to the heart to beat too forcibly is blunted.  BP thus falls.

BP begins to fall in 30-60 minutes with a peak BP reduction in 2-4 hours.  The “half-life” of Clonidine in circulation is 12-16 hours, such than when used as a maintenance BP control medication, Clonidine is usually administered twice a day.

Clonidine will dependably lower your BP.  The down side of Clonidine is a high frequency of nuisance side effects, namely dry mouth, fuzzy thinking, sedation, and sexual dysfunction.  We thus rarely use Clonidine as a maintenance therapy (typically only in anxious individuals with hypertension and insomnia). 

However, we can make good use of Clonidine to address BP spikes.  I will typically prescribe Clonidine 0.1 mg orally every three hour, as needed, if your systolic BP is above a target level (usually 170 mmHg but this will vary from patient to patient) or if your diastolic value is high (usually above 90 mmHg).  How you feel at the time of the BP spike is also taken into consideration.  For example, if you do not feel poorly and I know that your heart is normal, you could simply wait or take Clonidine only if your BP is above a higher target, say 180 mmHg.  Conversely, if you are feeling poorly and I know that you have underlying heart disease, it would make sense to take Clonidine at a lower BP level, say around 150 mmHg – these are individual recommendations that I will give you.  You may or may not experience a nuisance side effect with Clonidine, but as you will be taking Clonidine only infrequently, this should not be a major issue.

If your BP remains elevated at three hours, you can take a second dose, while if you are feeling poorly it makes sense to seek medical attention (again, this will be an individual recommendation; this handout is to provide general information).