Central Agonists (Alpha-2 Receptor Agonist)

Originally approved by the FDA in 1962, in recent years central agonists have gained more popularity. This is because of there ability to calm down withdrawal symptoms from drugs like opiates, benzodiazepines, and alcohol. They are also prescribed for ADHD in children, anxiety disorders, Tourettes syndrome, pain in cancer patients, and hypertension.

Also known as a centrally acting alpha agonists, alpha 2 receptor agonists, alpha 2 inhibitors, and central adrenergic inhibitors, these drugs work by decreasing stimulatory sensors from the brain and central nervous system. They stop nerve impulses in the brain which would cause excitement. They also excite a pathway which will inhibit the response of stimulating nerve endings. This causes the patient to be very relaxed and the blood vessels to be very relaxed. This action can reduce blood pressure at a rapid rate. That is why central agonists are often used in a hypertensive crisis situation. An average patient can expect to see extreme drops in blood pressure from this medication, causing a possible 40-60 point drop in systolic, and a possible 30-50 point drop in diastolic blood pressure numbers. They are powerful and there is no doubt whether or not they work for lowering blood pressure.

Central agonists are sedatives by nature, they can make the patient experience a feeling of extreme relaxation. This is why they are given to patients withdrawing from other illicit substances. In turn this can make them addictive. Patients who take central agonists for long periods of time will go through withdrawals that can mimic opioid withdrawals. If you or a loved one is experiencing signs and symptoms of addiction please contact an addiction specialist right away.

These drugs have been shown to work well in patients with renal impairment. It is important to note that central agonists are one of the more potent hypertensive drugs out there. And most medical professionals would not consider it a good first line treatment for uncomplicated hypertension. They are usually only used in uncomplicated hypertension if other less potent drugs have been administered and did not show signs of improvement for the patient. They are more often than not used in situations where a patients blood pressure is at a dangerously high level. 

Side effects of these drugs can be plentiful in some patients. They can include dizziness, feeling faint upon standing, lightheadedness, dry mouth, constipation, stomach issues, headaches, a feeling of general irritability, agitation, extreme fatigue, weakness, infections of the upper respiratory tract, insomnia, nightmares, a high heart rate, chest pain, swelling of the extremities, depression, hallucinating, memory problems, brain fog, inflammation of the joints, calf pain and soreness, and extreme blood pressure fluctuations.

One of the most common side effect patients experience from this medication is sedation. They can often feel like they are never fully energized even after a full nights sleep. However this is a mild side effect considering how harsh and debilitating other blood pressure med side effects can be.

Dizziness is a side effect many patients may experience when using central agonists. Sometimes more in the morning than at night. This can happen because of the way these drugs effect the body (widening the blood vessels in the brain), or this can happen simply because a patients blood pressure has become too low.

Kidney problems have happened before in patients taking central agonists. This is because the blood vessels in the kidneys can be widened to unsafe sizes with the use of the drug. The material the blood vessels are made out of may not tolerate this rapid and extensive increase in size. Many patients who had this side effect experienced hindered function of the kidneys, however kidney function returned to normal after discontinuation of the drug. Long term use may cause permanent kidney damage, just like with vasodilators like Hydralazine, but more research is needed to confirm this.

Long term use of central agonists may be associated with heart failure. Some medical professionals do believe these drugs can cause heart failure. This could be due to the fact that the heart may need a certain amount of compression on it to function properly, and using these drugs can cause the chambers and valves in the heart to have less pressure on them because of the extreme vasodilation effects. This pressure may be beneficial for proper heart function although some studies done by drug manufacturers say otherwise. Another theory is that the heart rate may be higher both at rest and under excursion with these drugs. The higher heart may cause issues within the cardiovascular system potentially leading to heart failure.

Atrioventricular blockages have happened in patients who took high dosages of central agonists. Although this has only been reported in patients who took high dosages, some medical professionals think it may be possible with long term use of moderate dosages. This is obviously a huge concern as blockages in the heart can cause death if left untreated.

One of the worst things associated with the use of central agonists is withdrawal. In many studies it has been shown that the high blood pressure rebound effect when stopping central agonists can be worse than any other blood pressure medication on the market. Rebound effects can cause a patients blood pressure to go much higher than it ever did before starting the drug. This happens for a few reasons. The sedation effect will also rebound, causing the patient to become very anxious during the withdrawal period. Also the nerve endings in the brain which were inhibited during the use of the drug, will be firing with more intensity than they did before ever starting the drug. It is important when discontinuing this one as with any blood pressure medication to taper down the dosage slowly over a period of time. Always consult with your doctor before stopping any medication.

It is important to note that central agonists can have adverse reactions with many different type of drugs. Including other blood pressure medications like beta blockers and calcium channel blockers. Be sure to double check that your doctor did not prescribe another medication along with a central agonist that could cause an adverse reaction.