ADRENERGIC AND ANTI-ADRENERGIC
DRUGS

Mr. D.Raju, M.pharm,
Lecturer

SYMPATHETIC NERVOUS SYSTEM

Fight or flight response results in:
1. Increased BP
2. Increased blood flow to brain, heart and

skeletal muscles
3. Increased muscle glycogen for energy
4. Increased rate of coagulation
5. Pupil dilation

ADRENERGIC RECEPTORS

Alpha—A1 and A2
Beta—B1, B2, B3
Dopamine—subsets D1-5

REVIEW OF FUNCTIONS OF SYMPATHETIC
NERVOUS SYSTEM RECEPTORS

Alpha 1—smooth muscle contraction
Alpha 2-negative feedback causes less
norepinephrine to be released so BP is reduced
Beta 1—increased heart rate
Beta 2—bronchodilation
Beta 3—actual site for lipolysis

MECHANISMS OF ACTION AND EFFECTS OF
ADRENERGIC DRUGS

Direct adrenergic drug action
Affects postsynaptic alpha 1 and beta
receptors on target effector organs
Examples: epinephrine, Isuprel,
norepinephrine, phenylephrine

MECHANISMS OF ACTION CONT.

2. Indirect adrenergic drug action occurs by
stimulation of postsynaptic alpha 1, beta 1 and
beta 2 receptors.Cause release of
norepinephrine into the synapse of nerve
endings or prevent reuptake of norepinephrine.
Examples include cocaine and TCAs

MECHANISMS OF ACTION CONT.

3. mixed action. Combination of direct and
indirect receptor stimulation
Examples are ephedrine and pseudoephedrine

MECHANISMS OF ACTION CONT.

Stimulation of alpha 2 receptors in CNS is
useful in decreasing BP
Most body tissues have both alpha and beta
receptors
Effect occurs 2ndary to receptor activated and
number of receptors in the particular body
tissue

MECHANISMS OF ACTION CONT.

Some drugs act on both receptors–dopamine
Some are selective–Isuprel

INDICATIONS FOR USE

Emergency drugs in treatment of acute
cardiovascular, respiratory and allergic
disorders
In children, epinephrine may be used to treat
bronchospasm due to asthma or allergic
reactions
Phenylephrine may be used to treat sinus
congestion

INDICATIONS OF ADRENERGICS CONT.

Stokes Adams
Shock
Inhibition of uterine contractions
For vasoconstrictive and hemostatic purposes

CONTRAINDICATIONS TO USE OF ADRENERGICS

Cardiac dysrhythmias, angina pectoris
Hypertension
Hyperthyroidism
Cerebrovascular disease
Distal areas with a single blood supply such as
fingers, toes, nose and ears
Renal impairment use caution

INDIVIDUAL ADRENERGIC DRUGS

Epinephrine—prototype
Effects include: increased BP, increased heart
rate, relaxation of bronchial smooth muscle,
vasoconstriction in peripheral blood vessels

EPINEPHRINE

Increased glucose, lactate, and fatty acids in
the blood due to metabolic effects
Increased leukocyte and increased coagulation
Inhibition of insulin secretion

EPINEPHRINE

Affects both alpha and beta receptors
Usual doses, beta adenergic effects on heart
and vascular smooth muscle will predominate,
high doses, alpha adrenergic effects will
predominate
Drug of choice for bronchospasm and laryngeal
edema of anaphylaxis

EPINEPHRINE

Excellent for cardiac stimulant and
vasoconstrictive effects in cardiac arrest
Added to local anesthetic
May be given IV, inhalation, topically
Not P.O

EPINEPHRINE

Physiologic antagonist to histamine
Those on beta blockers may need larger doses
Drug of choice in PEA. Vasopressin has now
become drug of choice in ventricular
tachycardia
Single dose of Vasopressin, 40 units IV

OTHER ADRENERGICS

Ephedrine is a mixed acting adrenergic drug.
Stimulates alpha and beta receptors. Longer
lasting than epinephrine.
See in Primatene mist

PSEUDOPHEDRINE

Used for bronchodilating and nasal
decongestant effects

ISUPREL (ISOPROTERENOL)

Synthetic catecholamine that acts on beta 1
and 2 receptors
Stimulates heart, dilates blood vessels in
skeletal muscle and causes bronchodilation
No alpha stimulation
Used in heart blocks (when pacemaker not
available) and as a bronchodilator

NEOSYNEPHRINE (PHENYLEPHRINE)

Pure alpha
Decreases CO and renal perfusion
No B1 or B2 effects
Longer lasting than epinephrine
Can cause a reflex bradycardia
Useful as a mydriatic

TOXICITY OF ADRENERGICS IN CRITICALLY ILL
PATIENTS

Affects renal perfusion
Can induce cardiac dysrhythmias
Increases myocardial oxygen consumption
May decrease perfusion of liver
Tissue necrosis with extravasation

ANTI-ADRENERGICS

Sympatholytic
Block or decrease the effects of sympathetic
nerve stimulation, endogenous catecholamines
and adrenergic drugs

ANTIADRENERGIC S—MECHANISMS OF ACTION
AND EFFECTS

Can occur by blocking alpha 1 receptors
postsynaptically
Or by stimulation presynaptic alpha 2
receptors. Results in return of norepineprhine
to presynaptic site. Activates alpha 2 resulting
in negative feedback. Decreases release of
additional norepinephrine.

ALPHA-ADRENERGIC AGONISTS AND BLOCKING
AGENTS

Alpha 2 agonists inhibit release of
norepinephrine in brain; thus, decrease effects
on entire body
Results in decrease of BP
Also affects pancreatic islet cells, thus some
suppression of insulin secretion

ALPHA 1 ADRENERGIC BLOCKING AGENTS

Act on skin, mucosa, intestines, lungs and
kidneys to prevent vasoconstriction
Effects: dilation of arterioles and veins,
decreased blood pressure, pupillary
constriction, and increased motility of GI tract

ALPHA 1 ADRENERGIC BLOCKING AGENTS

May activate reflexes that oppose fall in BP
such as fluid retention and increased heart rate
Can prevent alpha medicated contraction of
smooth muscle in nonvascular tissues
Thus, useful in treating BPH as inhibit
contraction of muscles in prostate and bladder

ALPHA 1 ANTAGONISTS

Minipress (prazosin)—prototype.
Hytrin (terazosin) and Cardura (doxazosin)—
both are longer acting than Minipress.

ALPHA 1 ANTAGONISTS CONT.

Flomax (tamsulosin). Used in BPH. Produces
smooth muscle relaxation of prostate gland
and bladder neck. Minimal orthostatic
hypotension.
Priscoline (tolaxoline) used for vasospastic
disorders. Pulmonary hypertension in
newborns. Can be given sub Q, IM or IV.

ALPHA 2 AGONISTS

Catapres (clonidine). PO or patch.
Tenex (guanfacine)
Aldomet (methyldopa). Can give IV. Caution in
renal and hepatic impairment.

BETA ADRENERGIC BLOCKING MEDICATIONS

Prevent receptors from responding to
sympathetic nerve impulses, catecholamines
and beta adrenergic drugs.

EFFECTS OF BETA BLOCKING DRUGS

Decreased heart rate
Decreased force of contraction
Decreased CO
Slow cardiac conduction
Decreased automaticity of ectopic pacemakers

EFFECTS OF BETA BLOCKING DRUGS

Decreased renin secretion from kidneys
Decreased BP
Bronchoconstriction
Less effective metabolism of glucose. May
result in more pronounced hypoglycemia and
early s/s of hypoglycemia may be blocker
(tachycardia)

EFFECTS OF BETA BLOCKING AGENTS

Decreased production of aqueous humor in eye
May increase VLDL and decrease HDL
Diminished portal pressure in clients with
cirrhosis

INDICATIONS FOR USE

Alpha 1 blocking agents are used for tx of
hypertension, BPH, in vasospastic disorders,
and in persistent pulmonary hypertension in
the newborn
May be useful in treating pheochromocytoma
May be used in Raynaud’s or frostbite to
enhance blood flow

REGITINE (PHENTOLAMINE)

Used for extravasation of potent
vasoconstrictors (dopamine, norepinephrine)
into subcutaneous tissues

INDICATIONS FOR USE

Alpha 2 agonists are used for hypertension—
Catapres
Epidural route for severe pain in cancer
Investigationally for anger management,
alcohol withdrawal, postmenopausal hot
flashes, ADHD, in opioid withdrawal and as
adjunct in anesthesia

BETA BLOCKING MEDICATIONS

Mainly for cardiovascular disorders (angina,
dysrhythmias, hypertension, MI and glaucoma)
In angina, beta blockers decrease myocardial
oxygen consumption by decreasing rate, BP
and contractility. Slow conduction both in SA
node and AV node.

BETA BLOCKERS

Possibly work by inhibition of renin, decreasing
cardiac output and by decreasing sympathetic
stimulation
May worsen condition of heart failure as are
negative inotropes
May reduce risk of “sudden death”

BETA BLOCKERS

Decrease remodeling seen in heart failure
In glaucoma, reduce intraocular pressur by
binding to beta-adrenergic receptors in ciliary
body, thus decrease formation of aqueous
humor

BETA BLOCKERS

Inderal (propranolol) is prototype
Useful in treatment of hypertension,
dysrhythmias, angina pectoris, MI
Useful in pheochromocytoma in conjunction
with alpha blockers (counter catecholamine
release)
migraines

BETA BLOCKERS

In cirrhosis, Inderal may decrease the
incidence of bleeding esophageal varices
Used to be contraindicated in heart failure, now
are standard
Known to reduce sudden death
Often given with ACEIs
Indications include: htn, angina, prevention of
MI