Pharm: Chapter 18

A patient who is taking epinephrine is also taking several other medications. The nurse should realize that there is a possible drug interaction with which drugs?

Metoprolol (Lopressor) Propranolol (Inderal) Digoxin (Lanoxin)

Terbutaline sulfate:

-Stimulates B2 -It's a bronchodilator used to correct bronchospasm

Drugs can prolong the action of the neurotransmitter (Norepinephrine) by:

(1) By inhibiting the norepinephrine reuptake, which prolongs the action of the transmitter OR (2) By inhibiting the degradation of norepinephrine by enzyme action

The 3 Classifications of Sympathomimetics:

(1) Direct-acting sympathomimetics- directly stimulate the adrenergic receptor (epinephrine or norepinephrine). (2) Indirect-acting sympathomimetics- stimulate the release of norepinephrine from the terminal nerve endings (amphetamine). (3) Mixed-action sympathomimetics- (both direct & indirect acting) stimulates the adrenergic receptor sites and stimulate the release of norepinephrine from the terminal nerve endings (ephedrine).

The 2 enzymes that inactivate the neurotransmitter (Norepinephrine) are:

(1) monoamine (MAO)- which is inside the neuron. (2) catechol-O-methyltransferase (COMT)- which is outside of the neuron.

Transmitters are inactivated by:

(1) reuptake of the transmitter back into the neuron (nerve cell terminal). (2) enzymatic transformation or degradation. (3) diffusion away from the receptor. -Note: -Norepinephrine reuptake plays a more important role in inactivation than the enzymatic action. -Following the reuptake of the transmitter in the neuron, the transmitter may be degraded or reused.

There are 2 drugs that affect the sympathetic nervous system:

(1)adrenergic agonists (sympathomimetics) (2)adrenergic blockers (sympatholytics)

Atenolol (Tenormin):

-A selective beta 1 blocker, that is one of the most frequently prescribed drugs in the US -It decreases sympathetic outflow to the periphery and suppresses the rein-angiotensin-aldosterone system response. -It is contraindicated in bradycardia, heart block, cardiogenic shock, pulmonary edema, acute bronchospasm, and pregnancy. -It decreases HR, peripheral vascular resistance, force of cardiac contractions, cardiac output, as well as systolic and diastolic B/P. -It can be taken IV or tablets PO once daily.

Inactivation of Neurotransmitters:

-After the neurotransmitter (norepinephrine) has performed its function, the action must be stopped to prevent prolonging effects.

Metaproterenol sulfate (Alupent):

-Stimulates B2 -Treats bronchospasm by bronchodilation

Albuterol:

-Albuterol sulfate (Proventil), is a beta 2-adrenergic agonist. -It is a selective for beta -adrenergic receptors, so the response is relaxation of bronchial smooth muscle and bronchodilation. -A patient w/ asthma may tolerate albuterol better than isoproterenol b/c albuterol's action is more selective (meaning it only activates B2 receptor). -By using selective sympathomimetics, fewer undesired adverse effects will occur. -However, high dosages of albuterol may affect B1 receptors, causing an increase in HR. -Albuterol sulfate (Proventil, Ventolin) is well absorbed in the GI tract and is extensively metabolized by the liver. The half-life differs according to route of administration. --The primary use of albuterol is to prevent and treat bronchospasm. -Inhalation is faster than oral administration, though the duration of action is the same for both. -Tremors, restlessness, and nervousness may occur. -If taken w/ an MAOI, hypertensive crisis can result. -Beta blockers may inhibit the action of albuterol.

Many of the Adrenergic Agonists stimulate more than one of the adrenergic receptor sites.

-An example is epinephrine (Adrenalin), which acts on A1, A2, B1, and B2 adrenergic receptor sites. -The responses from these receptor sites include increase in B/P, pupil dilation, increase in HR, and bronchodilation. >In Anaphylactic Shock, epinephrine is useful b/c it increases B/P, HR, and airflow through the lungs. -B/c epinephrine affects different adrenergic receptors, it is nonselective. Additional side effects result when more responses occur than are desired.

Alpha Blockers: (Also called Alpha-adrenergic blockers)

-Are drugs that block or inhibit a response at the alpha-adrenergic receptor site. -Alpha blockers are divided into 2 groups: (1) Selective alpha blockers that block A1 (2) Nonselective alpha blockers that block A1 and A2 -B/C Alpha blockers can cause orthostatic hypotension and reflex tachycardia, they are not prescribed as frequently as beta blockers. -Alpha blockers promote vasodilation, causing a decrease in B/P. If it is long-standing, orthostatic hypotension can result, along with dizziness and an increase HR. -Alpha blockers can be used to treat peripheral vascular disease (Raynaud's disease). When vasodilation occurs, it permits more blood flow to the extremities. -It also helps decrease symptoms of benign prostatic hypertrophy.

(2) Adrenergic Blockers (Sympatholytics):

-Are drugs that block the effects of adrenergic neurotransmitters. -Also known as (adrenergic antagonists or sympatholytics). -They act as antagonists to adrenergic agonists by blocking the alpha or beta receptor. -They block effects of adrenergic neurotransmitter. -Block alpha and beta receptor sites either Directly by occupying receptors or Indirectly by inhibiting release of neurotransmitters epinephrine and norepinephrine.

Adrenergic Neuron Blockers:

-Are drugs that block the release of norepinephrine from the sympathetic terminal neurons. -The clinical use of neuron blockers is to decrease B/P. >Reserpine is an example of a neuron blocker. -It's an antihypertensive agent. -The effects of this drug closely resemble those of A and B blockers. -It also reduces the serotonin and catecholamine transmitters. -Depletion of neurotransmitters may lead to severe mental depression. -Take this drug at the same time daily.

Beta Blockers:

-Are useful in treating mild to moderate hypertension, angina pectoris, and myocardial infarctions. >Side Effects: -bradycardia, hypotension, headache, dizziness, cold extremities, hypoglycemia, and bronchospasm.

Alpha 1 Receptor: (Location and Effects)

-Blood vessels: vasoconstriction, increased B/P,& increased contractibility of the heart. -Eye: mydriasis (pupil dilation) -Bladder: relaxation -Prostate: contraction >When Alpha 1 receptors in vascular tissues (vessels) of muscles are stimulated, the arterioles and venules constrict, increasing peripheral resistance and blood return to the heart. =Resulting in improved circulation and increased B/P. >When there's too much stimulation, blood flow is decreased to vital organs.

Catecholamines:

-Catecholamines are the chemical structures of a substance (endogenous or synthetic) that can produce a sympathomimetic response. -Ex: of Endogenous Catecholamines are epinephrine, norepinephrine, and dopamine. -Ex: of Synthetic Catecholamines are isoproterenol and dobutamine. >Noncatecholamines (phenylephrine, metaproterenol, and albuterol) stimulate the adrenergic receptors. -Most Noncatecholamines have a longer duration of action than Endogenous and Synthetic Catecholamines.

Beta Blockers: (Also known as Beta-adrenergic blockers)

-Decrease HR, and a decrease in B/P usually follows. -Nonselective beta blockers block B1 and B2. The HR decreases b/c of B1 blocking, but bronchoconstriction also occurs. Use extreme caution in patients who have COPD or Asthma when using Nonselective beta blockers.

Albuterol Continued...

-Drug class: Beta 2-adrenergic agonist -Trade names: Proventil, Ventolin -Pregnancy Category: C >Contraindications: -Cardiac dysrhythmias, coronary disease >Drug Interactions: -Increased effect will occur with other sympathomimetics, may increase effects w/ MAOIs and tricyclic antidepressants. >Uses/Effects: -it treats bronchospasm, asthma, bronchitis and other COPD. >Side Effects/ Adverse Reactions: -Tremor, dizziness, nervousness, restlessness, sweating, blurred vision, flushing, headache, hoarseness, pharyngitis, nasal congestion, insomnia, weakness, nausea, and diarrhea. -Palpitations, tachycardia, hypertension, hallucinations, seizures, hyperglycemia, & the life threatening cardiac dysrhythmias and Stevens-Johnson syndrome.

(1) Adrenergic Agonists (Sympathomimetics):

-Drugs that stimulate the sympathetic nervous system are called: Adrenergics, Adrenergic agonists, or sympathomimetics. -They mimic the sympathetic neurotransmitters norepinephrine and epinephrine. How? By acting on one or more adrenergic receptor sites located in the effector cells of muscles, such as the heart, bronchiole walls, gastrointestinal (GI) tract, urinary bladder, and ciliary muscle of the eye.

Epinephrine:

-Epinephrine can be administered subcutaneously, intravenously, topically, or by inhalation, intracardiac, and instillation methods. It is NOT give PO b/c of it's rapidly metabolized in the GI tract and liver resulting in unstable serum levels. -Epinephrine is metabolized by the liver and excreted in the urine and breast milk. -Epinephrine is used in emergencies to treat anaphylaxis. -It is a potent inotropic (strengthens myocardial contraction) drug that increases cardiac output, promotes vasoconstriction and systolic B/P elevation, increases HR, and produces bronchodilation. -High doses can result in cardiac dysrhythmias making it necessary for ECG monitoring. -Also, It can cause renal vasoconstriction, thereby decreasing renal perfusion and urinary output. -The use of decongestants with epinephrine has an additive effect -If given with Digoxin, cardiac dysrhythmias may occur. -Beta blockers can antagonize the action of epinephrine.

Epinephrine Continued...

-Epinephrine is nonselective, as it excites three different adrenergic receptors approximately equally. -Drug class: Sympathomimetic: adrenergic agonist -Trade name: Adrenalin -Pregnancy Category: C >Actions: -Alpha1 increases the blood pressure. -Beta1 increases heart rate. -Beta2 promotes bronchodilation. >Used for: -Anaphylaxis, anaphylactic shock -Bronchospasms -Cardiogenic shock, cardiac arrest -Severe Hypotension >Side effects: -Anorexia, nausea, vomiting, nervousness, tremors, agitation, sweating, headache, pallor, insomnia, weakness, and dizziness. >Adverse reactions: -Palpitations, tachycardia, hypertension, dyspnea. -Necrosis and gangrene of IV site upon infiltration. -Life-threatening- ventricular fibrillation and pulmonary edema. >Drug interaction: -Beta blockers-decrease epinephrine action. -Digoxin-causes cardiac dysrhythmias.

A selective beta blocker:

-If the desired effect is to decrease HR and B/P, then a selective beta1 blocker such as antenolol (Tenormin) or metoprolol tartrate (Lopressor) may be ordered.

NSAIDS:

-Interacts w/ Atenolol by decreasing its hypotensive effect. -When Atenolol is given with Atropine and other anticholinergic, absorption is increased. -The risk of hypoglycemia is increased if taken with insulin.

Clonidine: (Catapres)

-Is a selective A2 adrenergic agonist used to treat hypertension. -A2 drugs act by decreasing the release of norepinephrine from sympathetic nerves and decreasing peripheral adrenergic receptor activation. -A2 drugs also produce vasodilation by stimulating A2 receptors in the CNS, leading to a decrease in B/P.

Methyldopa: (Aldomet)

-Is an A1 adrenergic agonist that acts within the CNS. -This drug us taken up into the brainstem neurons and converted to methylnorepinephrine, which results in A2 activation. -The decrease of sympathetic outflow from CNS causes vasodilation and a reduction in B/P.

Intrinsic Sympathomimetic Activity (ISA):

-Is the ability of certain beta blockers to bind with a beta receptor to prevent strong agonists from binding to that receptor producing complete activation. -Nonselective beta blockers (B1 and B2) that have ISA include carteolol, carvedilol, penbutolol, and pindolol. -Selective beta blockers (blocks B1 only) that has ISA is acebutolol. -These agents may be recommended for patients experiencing bradycardia.

Another adrenergic receptor is Dopaminergic:

-It is located in the renal, mesenteric, coronary, and cerebral arteries. -When stimulated, the vessels dilate and blood flow increases. -*Only dopamine can activate this receptor!*

Nursing Process: Adrenergic Agonist-

-Know that adrenergic agonists are contraindicated if the patient has cardiac dysrhythmias, narrow-angle glaucoma, or cardiogenic shock. -Be sure to check their glucose level. -Inspect EpiPen for particles or discoloration prior to administration. Don't use if particles are pink to brown in color. Inject subcutaneously into outer thigh and hold in place for 5 to 10 seconds. Massage injection site for 10 seconds to promote absorption and reduce vasoconstriction and tissue irritation.

Beta 1 Receptor: (Location and Effects)

-Located in the kidney, but primarily in the heart. -Heart: increased heart contraction & increased HR -Kidney: increased renin secretion, increased angiotensin, & increased B/P >When stimulated, it increases myocardial contractibility and HR.

Alpha 2 Receptor: (Location and Effects)

-Located in the postganglionic sympathetic nerve endings. -Blood vessels: decreased B/P (reduced norepinephrine) -Smooth muscle (GI tract): decreased GI tone and motility >When stimulated, they inhibit the release of norepinephrine, leading to a decrease in vasoconstriction.= Resulting in vasodilation and a decrease in B/P.

What drugs are commonly used to illegally produce amphetamines and methamphetamines?

-Pseudoephedrine, ephedrine, and phenylpropanolamine (so basically, mixed-acting sympathomimetic drugs). -These are not OTC drugs, but can be obtained in limited amounts per month. Purchase log kept for at least 2 years.

Beta 2 Receptor: (Location and Effects)

-Smooth muscle (GI tract): decreased GI tone and motility -Lungs: bronchodilation -Uterus: relaxation of uterine smooth muscle (results in a decrease of uterine contraction) -Liver: activation of glycogenolysis and increased blood sugar

Phenylephrine HCI (12-hour spray):

-Stimulates A1 -Nasal decongestion used for common cold

Midodrine (ProAmatine):

-Stimulates A1 -Treats symptomatic orthostatic hypotension

Pseudoephedrine HCI:

-Stimulates A1 and B1 -OTC nasal decongestion

Dopamine HCI (Intropin):

-Stimulates A1 and B1 -Used to correct hypotension

Norepinephrine Bitartrate (Levophed):

-Stimulates A1 and B1 -Used to treat shock by potent vasoconstriction; increases B/P and cardiac output.

Ephendrine HCI, Sulfate:

-Stimulates A1, B1, B2 -Used to treat hypotensive states, bronchospasm, and nasal congestion.

Dobutamine HCI (Dobutrex):

-Stimulates B1 -Treats cardiac decompensation

Pseudoephedrine is an example of a mixed-acting sympathomimetic.

-This drug acts indirectly by stimulating the release of norepinephrine from the nerve terminals and acts directly on A1 and B1 receptors. -Like epinephrine, Pseudoephedrine increases the HR. -It is not as potent a constrictor as epinephrine, & there is less risk of hemorrhagic stroke and hypertensive crisis. -This drug can relieve nasal and sinus congestion w/o rebound congestion.

Propranolol Hydrochloride (Inderal):

-Was the first beta blocker prescribed to treat angina, cardiac dysrhythmias, hypertension, and heart failure. -This medication is giving for migraine prophylaxis. -It has many side effects b/c of its nonselective response in blocking B1 and B2 receptors.

Antagonists-

-drugs that block a response. -atropine, an antagonist, blocks the histamine (H2) receptor, thus preventing excessive gastric excretion.

Agonists-

-drugs that produce a response. -epinephrine (Adrenalin) stimulates beta1 and beta2 receptors, so it is an agonist.

Nonselective-

-excites/uses multiple receptors.

Selective-

-excites/uses one receptor.

There are many adrenergic receptors. The 4 main Adrenergic Receptors are:

Alpha 1, Alpha 2, Beta 1, and Beta 2.

The nurse is administering atenolol (Tenormin) to a patient. Which concurrent drugs does the nurse expect to most likely cause an interaction?

An NSAID, such as aspirin & atropine, an anticholinergic

Stimulation of which adrenergic receptor results in dilation of vessels and decrease in blood pressure?

Answer: Alpha 2 Rationale: When alpha2 receptors are stimulated, they inhibit the release of norepinephrine, leading to a decrease in vasoconstriction. This results in vasodilation and a decrease in blood pressure.

The nurse is teaching the patient about the side effects of atenolol (Tenormin). These include

Answer: Bronchospasm. Rationale: The side effects commonly associated with beta blockers are bradycardia, hypotension, headache, dizziness, cold extremities, hypoglycemia, and bronchospasm.

A patient has been prescribed atenolol (Tenormin). To ensure safe dosing, the nurse teaches the patient to frequently assess what parameter?

Answer: HR Rationale: The side effects commonly associated with atenolol (Tenormin), which is a beta blocker, include bradycardia, hypotension, headache, dizziness, cold extremities, hypoglycemia, and bronchospasm.

A patient is receiving dopamine (Intropin) intravenously. Which drug should the nurse have available to treat extravasation and tissue necrosis?

Answer: Phentolamine mesylate (Regitine) Rationale: The antidote for IV extravasation of dopamine is phentolamine mesylate (Regitine) 5 to 10 mg, diluted in 10 to 15 mL of saline infiltrated into the area. Norepinephrine bitartrate (Levophed) is an adrenergic agonist; nadolol (Corgard) is a beta1 and beta2 adrenergic blocker, and clonidine (Catapres) is a selective alpha2-adrenergic agonist (sympathomimetic) used primarily to treat hypertension.

A nurse is administering epinephrine to a patient during a cardiac arrest. The primary desired action of this medication is to

Answer: stimulate a heart rate. Rationale: Epinephrine is a potent inotropic (strengthens myocardial contraction) drug that increases cardiac output, promotes vasoconstriction and systolic blood pressure elevation, increases heart rate, and produces bronchodilation. High doses can result in cardiac dysrhythmias necessitating electrocardiogram (ECG) monitoring. Epinephrine can also cause renal vasoconstriction, thereby decreasing renal perfusion and urinary output.

A patient is prescribed metoprolol (Lopressor) to treat hypertension. It is important for the nurse to monitor the patient for which condition?

Bradycardia & Hypotension

Nadolol (Corgard) is prescribed for a patient. The nurse realizes that this is a beta-adrenergic blocker and that this drug classification is contraindicated for the patients with which condition?

Bronchial asthma

Sympathetic=

Fight or flight

A patient is given epinephrine (Adrenalin), an adrenergic agonist (sympathomimetic). The nurse should monitor the patient for which condition?

Increased B/P

The nurse realizes that beta 1 receptor stimulation is differentiated from beta 2 stimulation in that stimulation of beta 1 receptors leads to which condition?

Increased myocardial contractility

The nurse will monitor the patient taking albuterol (Proventil) for which conditions?

Palpations and Hypertension