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P A R T 9
Drugs acting on the renal system
C
onditions affecting the urinary tract and bladder are
common problems. These conditions include acute
urinary tract infections (UTIs), bladder spasms, bladder
pain and benign prostatic hyperplasia (BPH).
Females, with shorter urethras, are particularly
vulnerable to repeated urinary tract, bladder and even
kidney infections. Children also may have frequent
urinary tract problems. People with indwelling catheters
or intermittent catheterisations often develop bladder
infections or
cystitis
, which can result from bacteria
introduced into the bladder by these devices. Blockage
anywhere in the urinary tract can lead to backflow
problems and the spread of bladder infections into the
kidney (
pyelonephritis
). The signs and symptoms of a
UTI are uncomfortable and include
urinary frequency
,
urgency
, burning on urination (associated with cystitis),
and chills, fever, flank pain and tenderness (associated
with acute pyelonephritis). To treat these infections, cli-
nicians use specific urinary tract anti-infectives, which
include antibiotics, as well as specific agents that reach
antibacterial levels only in the kidney and bladder and
are thought to sterilise the urinary tract.
Drugs also are available to block spasms of the
urinary tract muscles, decrease urinary tract pain,
protect the cells of the bladder from irritation, and treat
enlargement of the prostate gland in men. Table 52.1
summarises urinary tract problems and the drugs of
choice to treat them. Box 52.1 highlights important
considerations related to urinary tract drugs based on
the person’s age.
URINARY TRACT ANTI-INFECTIVES
Urinary tract anti-infectives (Table 52.2) are of two
types. One type comprises the antibiotics, which are
particularly effective against the gram-negative bacteria
that cause most UTIs. The antibiotics used specifically
to treat UTIs include norfloxacin (
Noroxin, Roxin
) and
nitrofurantoin (
Macrodantin
). Ciprofloxacin (
Cifran
)
and sulfamethoxazole and trimethoprim (
Bactrim,
Resprim
) are also used frequently to treat UTIs but are
■■
TABLE 52.1
Urinary tract
problem
Drugs of choice
Infection
Urinary tract anti-infectives: hexamine
hippurate, nitrofurantoin, norfloxacin
Spasm
Antispasmodics: oxybutynin,
tolterodine
Pain
Bladder protectant for interstitial
cystitis: pentosan
Benign
prostatic
hyperplasia
Alpha-adrenergic blockers: alfuzosin,
tamsulosin, terazosin
Testosterone inhibitor: finasteride,
dutasteride
BOX 52.1
Drug therapy across the lifespan
Urinary tract agents
CHILDREN
Children may develop urinary tract infections (UTIs),
including cystitis, and need to be treated with a
urinary tract anti-infective. Some children, because of
congenital problems or indwelling catheters, require
other urinary tract agents such as urinary tract analgesics
or antispasmodics.The older anti‑infectives—such as
nitrofurantoin and hexamine hippurate—have established
paediatric guidelines. A child with repeated urinary tract
infections should be evaluated for potential sexual abuse.
Children need to be instructed in proper hygiene and
should not be given bubble baths if urinary tract infections
occur.They should be encouraged to avoid the alkaline ash
juices such as orange or grapefruit juice and urged to drink
lots of water.
If an antispasmodic is needed, oxybutynin is indicated
for children older than 5 years of age.
ADULTS
Adults need to be cautioned about the various measures
that can be used to decrease the likelihood of urinary tract
infections.They should be encouraged to drink plenty of
fluids to maintain bladder health.
If they are taking an anticholinergic to block spasm,
adults need to be advised of other precautions to take
when the parasympathetic system is blocked.
Adult men being treated for benign prostatic
hyperplasia need to be aware of the possibility of
decreased sexual function, as well as fatigue, lethargy
and the potential for dizziness, which could interfere with
working or activities of daily living.
PREGNANCY AND BREASTFEEDING
The use of urinary tract agents during pregnancy
should be approached with caution. Women who are
breastfeeding should use these agents with caution
because of the potential for adverse effects on the
baby, or they should find another method of feeding
the baby.
OLDER ADULTS
Older adults often have conditions that are treated with
the urinary tract agents.They are also more likely to have
renal or hepatic impairment, which requires caution in
the use of these drugs. Older adults should be started on
the lowest possible dose of the drug, and it should be
titrated slowly based on response. Special precautions
to monitor cardiac function, intraocular pressure, blood
pressure and bladder emptying need to be taken when
using alpha-adrenergic blockers with these people. Older
people may have a difficult time maintaining fluid intake
and might benefit from extra encouragement to drink
fluids, including cranberry juice, and to avoid alkaline ash
drinks.
