The document discusses various drug classes used to treat hypertension including central-acting alpha-2 agonists, peripheral-acting adrenergic antagonists, and direct vasodilators. Tables provide the generic names, brands, mechanisms of action, uses, dosage ranges, side effects to expect and report, and drug interactions for drugs in each class. Specifically, the tables outline drugs like clonidine, guanabenz, guanfacine, methyldopa, guanadrel, guanethidine sulfate, reserpine, and hydralazine which are used to treat hypertension through different mechanisms such as reducing sympathetic nervous system activity or directly relaxing blood vessels.

1. Table 16-9. Central-Acting Alpha-2 Agonists
Generic Name (Brand
name)
Dosage Range
Clonidine (Catapres,
Catapres-TTS)
PO: initial-0.1 mg twice daily
Maint:0.2-0.8 mg daily in divided doses
Max: 2.4 mg daily
Transdermal: initial- start with 2.5 mg
patch, after 2 weeks, add another 2.5 mg
patch or use a larger system; apply to
hairless area on intact skin on upper arm
or torso once every 7 days, use a different
site each week. Effect starts 2-3 days after
start of therapy.

2. Guanabenz (Wytensin) PO: initial - 4 mg twice daily;
increase 4-8 mg daily every 1-2
weeks
MAX:32 mg twice daily
Guanfacine (Tenex) MAX:32 mg twice daily
PO: initial – 1 mg HS
Maint: 1-2 mg
Max: 3 mg daily
Methyldopa (Aldomet) PO: initial – 250 mg 2-3 x a day
Maint: 500 mg – 3 g daily in 2-4
doses
Max: 3mg daily

3. Drug Class: Peripheral-acting adrenergic Antagonists
Table 16-10. Mechanism of Action, Use, and Dosage Range of
Peripheral-Acting Adrenergic Antagonists
Generic Name
(Brand Name)
Mechanism of
Action
Use Dosage Range
Guanadrel
(Hylorel)
It causes release
and depletion of
norepinephrine
from adrenergic
nerve endings.
PO:initial – 10
mg daily in two
divided doses.
Usual dosage
range:
20-75 mg
divided into 2-3
daily doses
Po: initial – 10
mg daily in two
divided doses.
Usual dosage
range: 20-75 mg
divided into 2-3
daily doses

4. Guanthidine
Sulfate
(Ismelin)
It depletes norepinephrine
from postganglionic
sympathetic nerve
terminals and inhibits the
release of norepinephrine
in response to sympathetic
nerve stimulation.
It is used in
refractometry
hypertension
uncontrolled by
other agents with
fewer side effects,
and is used in
combination with a
diuretic.
PO: initial-0.5
mg daily for 1-
2 weeks
Maint: 0.1-0.25
mg daily
Reserpine(Ser
pasil)
Respine is an alkaloid
obtained from the root of
Rauwolfia. It reduces
norepinephrine levels in
peripheral nerve endings
which slows heart rates
and minimizes peripheral
vascular resistance.
Extremely long
duration of action
maximum effect in
2-6 weeks. It is
used for Stage 1
hypertension.
Po: initial – 0.5
mg daily for 1-
2 week Maint:
0.1-0.25 mg
daily

5. Table 16-11. Side Effects to Expect/Report and Drug
Interaction of Peripheral-Acting Andrenergic Antagonists
Generic Name
(Brand Name)
Side Effects to
Expect/Report
Drug Interaction
Guanadrel
(Hylorel)
Orthostatic hypotension
is increased with
alcohol consumption or
prolonged standing
with little movement as
well sedation and
lethargy.
Drugs that enhance
therapeutic and toxic effects
include guanethidine,
barbiturates, disopyramide,
quinidine, diuretics,
tranquilizers, antihistamines,
alcohol, beta-adrenergic
blockers (propanolol, atenolol,
pindolol), diuretics, and other
antihypertensive drugs.

6. Guanethidine
sulfate
(Ismelin)
Light-headedness and
weakness due to arteriolar
and venous vasodilation
allow pools of blood to
collect in lower
extremities.
Drugs that enhance therapeutic
and toxic effects include
guanethidine, barbiturates,
disopyramide, quinidine,
diuretics, tranquilizers,
antihistamines, alcohol, beta-
adrenergic blockers
(propanolol, atenolol, pindolol),
diuretics, and other
antihypertensive drugs.
Guanethidine
sulfate
(Ismelin)
Light-headedness and
weakness due to arteriolar
and venous vasodilation
allow pools of blood to
collect in lower
extremities.
Drugs that reduce thrapeutic
and toxic effects include
tricyclic antidepressants
(amitriptylines, imimpramine),
amphetamines, ephedrine,
phenothiazides, and
haloperidol.

7. Reserpine
(Serpasil)
Nasal stuffiness, gastric
symptoms like diarrhea
and stomach cramp.
Report depression and
assess affective
(loneliness, sadness,
anxiety, and anger),
cognitive (confusion,
ambivalence, loss of
interest), and behavioral
responses (agitation, and
withdrawal) as well as the
occurence of nightmares
and insomia.
Drugs that enhance
therapeutic and toxic effects:
phenothiazines, procainamide,
disopyramide, thiothixene,
quinidine, diuretics,
tranquilizers, antihistamines,
alcohol, beta-adrenergic
blockers (propanol, atenolol,
pindolol), and other
antihypertensive drugs.
Drugs that reduce therapeutic
effects: tricyclic
antidepressants
(amitriptyline, imipramine,
doxepin).

8. Drug Class: Direct Vasodilators
Table 16-12. Mechanism of Action, Use, Dosage Range of
Direct Vasdilators
Generic Name
(Brand Name)
Mechanism of
Action
Use(Pregnancy
Category)
Dosage Range
Hydralazine
(Apresoline)
It causes direct
arteriolar smooth
muscle relaxation.,
resulting in reduced
peripheral vascular
resistance which, in
turn, causes a reflex
increase in heart
rate, cardiac output,
and renin release
with sodium and
water retention.
It is used for treating
Stage 2 hypertension
and hypertension
associated with renal
disease and toxemia
of pregnancy. It
provides
synpotomatic relief
in patients with heart
failure by reducing
resistance (overload)
to left ventricular
output.
PO:initial – 10
mg q.i.d. for the
first 2-4 days,
then 25 mg q.i.d.
daily.
For 2nd week,
increase dosage
to 50 mg q.i.d.
IM IV: 20-40 mg
repeated prn

9. Generic Name
(Brand Name)
Mechanism of
Action
Use(Pregnancy
Category)
Dosage Range
Hydralazine
(Apresoline)
It causes direct
arteriolar smooth
muscle relaxation.,
resulting in
reduced peripheral
vascular resistance
which, in turn,
causes a reflex
increase in heart
rate, cardiac
output, and renin
release with
sodium and water
retention.
It is used for
treating Stage 2
hypertension and
hypertension
associated with
renal disease and
toxemia of
pregnancy. It
provides
synpotomatic relief
in patients with
heart failure by
reducing resistance
(overload) to left
ventricular output.
PO:initial – 10
mg q.i.d. for the
first 2-4 days,
then 25 mg
q.i.d. daily.
For 2nd week,
increase dosage
to 50 mg q.i.d.
IM IV: 20-40 mg
repeated prn