page106
2.2.2
Loop diuretics
Loop diuretics are used in pulmonary oedema due to
left ventricular failure;
intravenous administration pro-
duces
relief
of
breathlessness
and reduces
pre-load
sooner than would be expected from the time of onset
of diuresis. Loop diuretics are also used in patients with
chronic heart failure.
Diuretic-resistant oedema (except
lymphoedema and oedema due to peripheral
venous
stasis or calcium-channel blockers) can be treated with a
loop diuretic combined with a thiazide or related diure-
tic (e.g.
bendroflumethiazide 5–10 mg daily or
meto-
lazone 5–20 mg daily).
If necessary, a loop diuretic can be added to antihyper-
tensive treatment
to achieve better
control
of
blood
pressure in those with resistant
hypertension,
or
in
patients with impaired renal function or heart failure.
Loop diuretics inhibit reabsorption from the ascending
limb of
the loop of
Henle
´
in the renal
tubule and are
powerful diuretics.
Furosemide and bumetanide are similar
in activity;
both act within 1 hour of oral
administration and diur-
esis is complete within 6 hours so that, if necessary, they
can be given twice in one day without interfering with
sleep. Following intravenous administration they have a
peak effect within 30 minutes.
The diuresis associated
with these drugs is dose related.
Torasemide has properties similar to those of
furose-
mide and bumetanide, and is indicated for oedema and
for hypertension.
Cautions
Hypovolaemia and hypotension should be
corrected before initiation of treatment with loop diur-
etics; electrolytes should be monitored during treatment
(see also Potassium Loss,
section 2.2).
Loop diuretics
can exacerbate diabetes (but
hyperglycaemia is
less
likely than with thiazides)
and gout.
If
there is
an
enlarged prostate, urinary retention can occur, although
this is less likely if small doses and less potent diuretics
are used initially; an adequate urinary output should be
established before initiating treatment;
interactions:
Appendix 1 (diuretics).
Contra-indications
Loop diuretics should be avoided
in severe hypokalaemia,
severe hyponatraemia,
anuria,
comatose and precomatose states associated with liver
cirrhosis,
and in renal
failure due to nephrotoxic or
hepatotoxic drugs.
Hepatic impairment
Hypokalaemia induced by loop
diuretics may precipitate hepatic encephalopathy and
coma—potassium-sparing diuretics can be used to pre-
vent this.
Renal impairment
High doses of loop diuretics may
occasionally be needed; high doses or rapid intravenous
administration can cause tinnitus and deafness;
high
doses of
bumetanide can also cause musculoskeletal
pain.
Pregnancy
Furosemide and bumetanide should not be
used to treat
gestational
hypertension because of
the
maternal
hypovolaemia associated with this condition.
Side-effects
Side-effects of loop diuretics include mild
gastro-intestinal
disturbances,
pancreatitis,
hepatic
encephalopathy,
postural
hypotension,
temporary
increase in serum-cholesterol
and triglyceride concen-
tration,
hyperglycaemia (less common than with thi-
azides), acute urinary retention, electrolyte disturbances
(including hyponatraemia,
hypokalaemia (see section
2.2),
hypocalcaemia,
hypochloraemia,
and
hypo-
magnesaemia),
metabolic
alkalosis,
blood
disorders
(including bone-marrow depression, thrombocytopenia,
and leucopenia),
hyperuricaemia,
visual
disturbances,
tinnitus and deafness (usually with high parenteral doses
and rapid administration, and in renal impairment), and
hypersensitivity reactions (including rash,
photosensit-
ivity,
and pruritus).
FUROSEMIDE
(Frusemide)
Indications
oedema (see notes above);
resistant
hypertension (see notes above)
Cautions
see notes above; also hypoproteinaemia may
reduce diuretic effect and increase risk of side-effects;
hepatorenal syndrome;
intravenous administration
rate should not usually exceed 4 mg/minute, however
single doses of up to 80 mg may be administered more
rapidly
Contra-indications
see notes above
Hepatic impairment
see notes above
Renal impairment
see notes above; also lower rate of
infusion may be necessary
Pregnancy
see notes above
Breast-feeding
amount too small to be harmful;
may
inhibit lactation
Side-effects
see notes above;
also intrahepatic
cholestasis and gout
Dose
. By mouth,
oedema,
initially 40 mg in the morning;
maintenance 20–40 mg daily;
CHILD
under 18 years
see
BNF for Children
Resistant oedema,
80–120 mg daily
Resistant hypertension,
40–80 mg daily
.
By intramuscular injection
or
slow intravenous
injection (rate of administration, see Cautions above),
initially 20–50 mg,
increased if necessary in steps of
20 mg not less than every 2 hours; doses greater than
50 mg
by intravenous infusion only; max.
1.5 g daily;
CHILD
under 18 years see
BNF for Children
Furosemide
(Non-proprietary) A
Tablets
, furosemide 20 mg, net price 28 = 81p; 40 mg,
28 = 84p;
500 mg,
28 = £4.05
Brands include
Rusyde
c
Oral solution
,
sugar-free,
furosemide,
net price
20 mg/5 mL,
150 mL = £13.97;
40 mg/5 mL, 150 mL
= £18.19;
50 mg/5 mL, 150 mL = £19.35
Brands include
Frusol
c
(contains alcohol
10%)
Injection
, furosemide 10 mg/mL, net price 2-mL amp
= 30p,
5-mL amp = 38p,
25-mL amp = £2.50
Lasix
c
(Sanofi-Aventis) A
Injection
, furosemide 10 mg/mL, net price 2-mL amp
= 75p
Note
Large-volume furosemide injections also available;
brands
include
Minijet
c
BUMETANIDE
Indications
oedema (see notes above)
Cautions
see notes above
Contra-indications
see notes above
86
2.2.2 Loop diuretics
BNF 61
2
Cardiovascular system