Pharmacology and continence
This topic will be addressed in terms
of drugs which may be used to treat incontinence and those which may be
aetiological.
Treatments
Laxatives
Bulk laxatives, (lumen acting)
* Increase
volumes in the gut so stimulate peristalsis
*
Indigestible
polysaccharides, methylcellulose and lactulose.
* Osmotic
agents, magnesium sulphate, epsom salts
Stimulant laxatives, (wall acting)
* Increase
motility, often acting on nerve plexuses
* May
cause abdominal cramps
* Bisacodyl,
senna, cascara
Lubricants, (mucosa acting)
* Soften
and/or lubricate
* Dioctyl
sodium, sulphosuccinate, liquid paraffin
Antidiarrhoeal drugs
Rehydration therapy
* Water
glucose and electrolytes
Antimotility drugs
* Morphine,
dipheroxylate and codeine inhibit ACh release from the myenteric plexus
* Loperamide
is best for GI action as it does not easily enter the brain
Absorbants
* Kaolin,
little evidence of effectiveness
Antibiotics
* Eg.
tetracycline for severe bacterial dysentry and cholera.
* Most
diarrhoea is viral in the UK, but remember protozoa
Antimicrobial drugs
Factors
* Sensitivity
* Resistance
* Compliance
Inhibitors of nucleic acid synthesis
* Sulphonamides,
trimethoprim, quinolones
Inhibitors of cell wall synthesis
* Penicillins,
cephlosporins and vancomycin
* Peptidoglycan
transpeptidase
Inhibitors of bacterial protein
synthesis
* Aminoglycosides,
tetracyclines, chloramphenicol, erythromycin
Anticholinergic and antispasmodics
Indicated in frequency, urgency and
incontinence
Lower intravesicular pressure so
increase capacity
Reduce frequency of contraction by
blocking parasympathetic innervation
Some have a direct spasmolytic effect
on the detrusor muscle.
Egs.
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CI
SP
ADR
Cholinergics and anticholinesterases
Used in urinary retention
Promote voiding by increasing detrusor
tone
Stimulate cholinergic receptors in
other organs
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SP
ADR
Selective alpha 1 blockers
Symptomatic treatment of benign
prostatic hypertrophy, (BPH)
In BPH increased sympathetic tone
constricts muscle in the urethra and prostate gland
These drugs remove this component of
the obstruction
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SP
ADR
5 - alpha reductase inhibitor
Indicated in BHP
Blocks the formation of
dihydrotestosterone, therefore induces shrinkage of the hyperplastic prostatic
tissue
Vasopressin analogue
In enuretic patients levels of ADH
have been shown to be low
Supplementation of the natural hormone
prevents overnight polyuria
May also be of benefit in multiple
sclerosis
No effects occur on vasotone or on
smooth muscle
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SP
ADR
Antifungal and antibacterial
Preparations used for bladder
instillation or irrigation
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SP
ADR
Local anaesthetics
Concentration
Route
Time to take effect
Aetiological factors
Diuretics
Thiazides
* Act
on distal tubule to inhibit NaCl reabsorption
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SP
ADR
Loop Diuretics
* Act
on thick ascending loop and distal tubule to inhibit NaCl reabsorption
Egs
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SP
ADR
Potassium sparing diuretics
* Act
on aldosterone responsive segments of distal nephron where K+ homeostasis is controlled
* Spirolactone,
amiloride, triamtereme, alcohol
Anticholinergic
Reduce the cholinergically mediated
parasympathetic supply to the gut. Possibility of GI obstruction in extreme
cases.
Other possible drugs which may effect
continence
Sedatives, Beta blockers, Analgesics, Anti-diabetic,
Anti-Parkinsons,
Oestrogen replacement