page132
Guanethidine, which also depletes the nerve endings of
noradrenaline,
is licensed for
rapid control
of
blood
pressure,
however alternative treatments are preferred
(see section 2.5).
GUANETHIDINE MONOSULPHATE
U
Indications
hypertensive crisis (but no longer recom-
mended—see section 2.5)
Cautions
coronary or cerebral arteriosclerosis,
asthma,
history of peptic ulceration;
interactions:
Appendix 1 (adrenergic neurone blockers)
Contra-indications
phaeochromocytoma,
heart fail-
ure
Renal impairment
reduce dose if eGFR 40–65 mL/
minute/1.73 m
2
;
avoid if eGFR less than 40 mL/min-
ute/1.73 m
2
Pregnancy
postural hypotension and reduced utero-
placental perfusion;
should not be used to treat
hypertension in pregnancy
Side-effects
postural hypotension,
failure of ejacula-
tion,
fluid retention,
nasal congestion,
headache,
diarrhoea,
drowsiness
Dose
. By intramuscular injection, 10–20 mg, repeated after 3
hours if required
Ismelin
c
(Amdipharm) A U
Injection
, guanethidine monosulphate 10 mg/mL, net
price 1-mL amp = £1.56
2.5.4
Alpha-adrenoceptor
blocking drugs
Prazosin has post-synaptic alpha-blocking and vasodi-
lator properties and rarely causes tachycardia.
It may,
however,
reduce blood pressure rapidly after the first
dose and should be introduced with caution.
Doxazo-
sin,
indoramin,
and terazosin have properties similar
to those of prazosin.
Alpha-blockers can be used with other antihypertensive
drugs in the treatment of resistant hypertension (section
2.5).
Prostatic hyperplasia
Alfuzosin,
doxazosin,
indor-
amin,
prazosin,
tamsulosin,
and terazosin are indicated
for benign prostatic hyperplasia (section 7.4.1).
DOXAZOSIN
Indications
hypertension (see notes above); benign
prostatic hyperplasia (section 7.4.1)
Cautions
care with initial dose (postural hypotension);
pulmonary oedema due to aortic or mitral stenosis;
cataract surgery (risk of intra-operative floppy iris
syndrome); heart failure;
interactions: Appendix 1
(alpha-blockers)
Driving
May affect performance of skilled tasks e.g. driving
Contra-indications
history of hypotension;
mono-
therapy in overflow bladder or anuria
Hepatic impairment
use with caution; manufacturer
advises avoid in severe impairment—no information
available
Pregnancy
no evidence of teratogenicity;
manufac-
turers advise use only when potential benefit out-
weighs risk
Breast-feeding
accumulates in milk—manufacturer
advises avoid
Side-effects
see section 7.4.1;
also dyspnoea,
cough-
ing;
fatigue,
vertigo,
paraesthesia, sleep disturbance,
anxiety; influenza-like symptoms; back pain, myalgia;
less commonly
weight changes,
angina,
myocardial
infarction,
hypoaesthesia,
tremor,
agitation,
micturi-
tion disturbance,
epistaxis,
arthralgia,
tinnitus,
and
gout;
very rarely
cholestasis,
hepatitis,
jaundice,
bradycardia, arrhythmias, bronchospasm, hot flushes,
gynaecomastia,
abnormal ejaculation,
leucopenia,
thrombocytopenia,
and alopecia
Dose
. Hypertension,
1 mg daily,
increased after 1–2 weeks
to 2 mg once daily, and thereafter to 4 mg once daily, if
necessary;
max.
16 mg daily
Doxazosin
(Non-proprietary) A
Tablets,
doxazosin (as mesilate) 1 mg,
net price 28-
tab pack = 93p; 2 mg, 28-tab pack = 99p; 4 mg, 28-tab
pack = £1.39.
Counselling,
initial dose,
driving
Brands include
Doxadura
c
Cardura
c
(Pfizer) A
Tablets
, doxazosin (as mesilate) 1 mg, net price 28-tab
pack = £10.56;
2 mg,
28-tab pack = £14.08.
Counsel-
ling,
initial dose,
driving
Modified-release
Doxazosin
(Non-proprietary) A
Tablets
,
m/r,
doxazosin (as mesilate) 4 mg,
net price
28-tab pack = £6.33.
Label:
25,
counselling,
initial
dose,
driving
Dose
hypertension,
benign prostatic hyperplasia,
4 mg once
daily,
increased to 8 mg once daily after 4 weeks if necessary
Brands include
Doxadura
c
XL
,
Raporsin
c
XL
,
Slocinx
c
XL
Cardura
c
XL
(Pfizer) A
Tablets
,
m/r,
doxazosin (as mesilate) 4 mg,
net price
28-tab pack = £5.70;
8 mg,
28-tab pack = £9.98.
Label:
25,
counselling,
driving,
initial dose
Dose
hypertension,
benign prostatic hyperplasia,
4 mg once
daily,
increased to 8 mg once daily after 4 weeks if necessary
INDORAMIN
Indications
hypertension (see notes above); benign
prostatic hyperplasia (section 7.4.1)
Cautions
avoid alcohol (enhances rate and extent of
absorption);
control incipient heart failure before
initiating indoramin;
elderly; Parkinson’s disease
(extrapyramidal disorders reported); epilepsy (con-
vulsions in
animal
studies);
history of depression;
cataract surgery (risk of intra-operative floppy iris
syndrome); interactions: Appendix 1 (alpha-blockers)
Driving
Drowsiness may affect performance of skilled tasks
(e.g. driving); effects of alcohol may be enhanced
Contra-indications
established heart failure
Hepatic impairment
manufacturer advises caution
Renal impairment
manufacturer advises caution
Pregnancy
no evidence of teratogenicity;
manufac-
turers advise use only when potential benefit out-
weighs risk
Breast-feeding
no information available
Side-effects
see section 7.4.1;
also sedation;
less
commonly
fatigue,
weight gain,
failure of ejaculation;
112
2.5.4 Alpha-adrenoceptor blocking drugs
BNF 61
2
Cardiovascular system