Alpha-2 adrenergic agonists: Nursing pharmacology

Alpha-2 adrenergic agonists are medications that oppose the effects of the sympathetic nervous system, ultimately decreasing smooth muscle contraction.

These medications include clonidine, guanfacine, and methyldopa, which can be administered orally, and clonidine also transdermally, to treat hypertension.

In addition, clonidine can also be used orally to treat attention deficit hyperactivity disorder, or ADHD for short, and less frequently, through epidural infusion for pain management in cancer.

Finally, methyldopa can also be administered intravenously to treat hypertensive crises. Once administered, alpha-2 adrenergic agonists act in the brainstem.

Normally, neurons in the brainstem carry signals to the spinal cord nuclei, where they synapse and release norepinephrine to stimulate the sympathetic nervous system.

This triggers the fight or flight response, which results in smooth muscle contraction, in turn leading to an increase in the heart rate and blood pressure, as well as decreasing gastrointestinal motility and urination by contracting the sphincters.

Now if we zoom into this synapse, we can see that some of the norepinephrine turns around and binds to alpha-2 adrenergic receptors.

This inhibits further release of norepinephrine and serves as a mechanism of negative feedback control. So, alpha-2 adrenergic agonists work by stimulating these receptors, therefore blocking the downstream sympathetic response, and ultimately decreasing blood pressure.Some common side effects include nausea, vomiting, constipation, and dry mouth.

Some clients may also experience bradycardia, while clonidine can also cause rebound hypertension when stopped abruptly, as well as CNS depression.

On the other hand, guanfacine and methyldopa can also cause orthostatic hypotension and sedation. In addition, methyldopa can also cause granulocytopenia, thrombocytopenia, and hemolytic anemia, as well as hepatotoxicity and hepatic necrosis.As far as contraindications go, these medications should be used with caution during pregnancy and breastfeeding, in children and elderly clients, as well as in clients with cardiovascular, cerebrovascular, or renal disease.

In addition, clonidine has a boxed warning against epidural use for obstetrical, postpartum, or perioperative pain management, due to the risk of hypotension and bradycardia.

Epidural administration is also contraindicated in clients with bleeding disorders or who are taking anticoagulants; and it can’t be administered above the C4 dermatome.

Finally, methyldopa is contraindicated in clients with active hepatic disease, as well as in those taking MAO inhibitors.Regarding interactions, clonidine increases the risk of bradycardia when combined with verapamil or diltiazem, and could cause life-threatening elevations of blood pressure if taken with beta-blockers.

On the other hand, methyldopa can increase lithium toxicity, the hypertensive effect of MAO inhibitors, and the risk of hypotension and CNS toxicity of levodopa.

Now, when caring for a client with hypertension who has been prescribed transdermal clonidine, first perform a baseline assessment including vital signs, especially blood pressure and heart rate.Then, review recent laboratory test results such as renal function.

Okay, moving on to client education. First, tell your client that their medication will help reduce their blood pressure and instruct them to apply their transdermal patch every 7 days at a consistent time each week.

Then, demonstrate how to apply the transdermal patch, and explain that the patch needs to be applied to clean, dry, intact, and hairless skin, preferably the chest or upper arm, and remind them to rotate the application site each time.

Show them how to dispose of a used patch by folding the sticky sides together, and discarding it in the trash away from pets and children.

Also remind them that they can leave their patch on while showering, bathing, or swimming. Lastly, ensure your client understands to never abruptly stop taking their medication because of the risk of rebound hypertension, and prompt them to notify their healthcare provider if they experience symptoms of hypertension, which can include sweating, flushing, nervousness, severe headache, and blurred vision.Next, review with your client some of the side effects they could experience.

Side effects like nausea, vomiting, and constipation can be managed by eating smaller, more frequent meals, increasing fluids, and consuming more fiber-rich foods like fruits, vegetables, and whole grains.

If they experience dry mouth, suggest they use sugar-free hard candy or gum, and take frequent sips of water. Drowsiness can be reduced by avoiding alcohol or other medications that depress the central nervous system; and caution them to avoid activities that require alertness, such as driving, until they adjust to the medication.

Lastly, let them know that the medication can cause dizziness, bradycardia, and hypotension; and remind them to make position changes slowly and use caution when going up and down stairs.Now, to assist your client with their blood pressure management, stress the importance of lifestyle modifications that can help control their blood pressure, such as weight loss, smoking cessation, increased physical activity as tolerated, and following a low sodium diet.

Teach your client how to check their own blood pressure and heart rate at home, and explain abnormal readings that warrant the need to seek medical attention.

Finally, while caring for a client receiving clonidine, continue to monitor for the development of side effects, and evaluate for the therapeutic response of a blood pressure within a normal range.

Alright, as a quick recap … Alpha-2 adrenergic agonists are medications that oppose the effects of the sympathetic nervous system, ultimately decreasing smooth muscle contraction; and include clonidine, guanfacine, and methyldopa.

Alpha-2 adrenergic agonists work by stimulating the alpha-2 adrenergic receptors, thereby blocking the downstream sympathetic response, and ultimately decreasing blood pressure.

Some common side effects include nausea, vomiting, constipation, and dry mouth; as well as bradycardia, central nervous system depression, and rebound hypertension when stopped abruptly.

When caring for a client prescribed an alpha-2 adrenergic agonist, nursing considerations include performing a baseline assessment, as well as monitoring for side effects and the desired therapeutic effect.

Client teaching is focused on safe self-administration, as well as learning to recognize side effects, and when to notify the healthcare provider.