Genitourinary Flashcards
α-blockers : Examples
- Doxazosin
- Tamsulosin
- Alfuzosin
α-blockers : Indications
1) 1st line in BPH
2) Add-on treatment in resistant hypertension
α-blockers : MOA
- α1-adrenoceptors are found mainly in smooth muscle, including in blood vessels and the urinary tract (the bladder neck and prostate in particular).
- Stimulation induces contraction; blockade induces relaxation.
- α1-blockers therefore cause vasodilatation and a fall in blood pressure (BP), and reduced resistance to bladder outflow.
α-blockers : Adverse Effects
- Postural hypotension
- Dizziness
- Syncope
(most prominent after 1st dose)
α-blockers: Contraindications
- Existing postural hypotension
α-blockers: Interactions
- Other anti-hypertensive (may be intentionally used for therapeutic aim)
- -> omit 1 dose of other anti-hypertensives when starting this medication
α-blockers : Prescribing
- Oral
- Best to take at night time
α-blockers: Monitoring
- Efficacy dependent on urinary symptoms
α-blockers: Patient Education
- Explain about side effect after 1st dose
Antimuscarinics - Examples
- Oxybutynin
- Tolterodine
- Solifenacin
Antimuscarinics - Indications
- Reduce urinary frequency, urgency and urge incontinence in overactive bladder
Antimuscarinics - MOA
- Antimuscarinic drugs bind to muscarinic receptors, where they act as a competitive inhibitor of acetylcholine.
- Contraction of the smooth muscle of the bladder is under parasympathetic control.
- Blocking muscarinic receptors therefore promotes bladder relaxation, increasing bladder capacity.
- In patients with overactive bladder, this may reduce urinary frequency, urgency and urge incontinence.
- Antimuscarinics help in overactive bladder through antagonism of the M3 receptor, which is the main muscarinic receptor subtype in the bladder.
- Solifenacin is more selective for the M3 receptor, which may reduce side effects.
Antimuscarinics - Adverse Effects
- Dry mouth
- Tachycardia, constipation + blurred vision
- Urinary retnetion
Antimuscarinics - Contraindications
- UTI
Antimuscarinics - Caution
- Elderly especially with dementia
- Angle-closure glaucoma : dangerous rise in intraocular pressure
- Arrhythmias
- Urinary retention
Antimuscarinics - Interactions
- Tricyclic antidepressants (causes more adverse effects)
Antimuscarinics - Prescribing
- only prescribe for urge incontinence after an adequate trial of bladder retraning
Antimuscarinics - Monitoring
- Review within a month of starting therapy to check response and SE
Antimuscarinics - Patient education
- Medication relaxes bladder
- reduces how often they need to pass water
- Explain SE - dry mouth
- Safety net- in elderly, stop if there is drowsiness and confusion
Phosphodiesterase (type 5) inhibitors : Examples
Sildenafil
Phosphodiesterase (type 5) inhibitors: Indications
1) Erectile dysfunction
2) Primary pulmonary hypertension
Phosphodiesterase (type 5) inhibitors : MOA
- PDE type 5 (PDE-5) is found predominantly in the smooth muscle of the corpus cavernosum of the penis and arteries of the lung.
- For an erection to occur, sexual stimulation is required.
- This releases nitric oxide (NO), which stimulates cyclic guanosine monophosphate (cGMP) production, causing arterial smooth muscle relaxation, vasodilatation and penile engorgement.
- As PDE-5 is responsible for the breakdown of cGMP, inhibition of this enzyme by sildenafil increases cGMP concentrations, improving penile blood flow and erection quality.
- Sildenafil does not cause an erection without sexual stimulation.
- In the pulmonary vasculature, sildenafil causes arterial vasodilatation by similar mechanisms and so is used to treat primary pulmonary hypertension.
Phosphodiesterase (type 5) inhibitors : Adverse Effects
SE due to vasodilator:
- Flushing
- Headache
- Dizziness
- Nasal congestion
More serious:
- Hypotension
- Tachycardia
- Palpitation
- Visual disorders (colour distortion)
Phosphodiesterase (type 5) inhibitors : Contraindication
- Stroke
- ACS
- Cardiovascular disease
Phosphodiesterase (type 5) inhibitors : Caution
- Hepatic or renal impairment
Phosphodiesterase (type 5) inhibitors : Interactions
Should not be prescribe with:
- nitrated or nicorandil
(increases nitric oxide conc, increased vasodilation)
Caution with other vasodilators:
- α-blockers
- CCB
Cytochrome P450 inhibitors:
- e.g. amiodarone, diltiazem + fluconazole
- SE increased
Phosphodiesterase (type 5) inhibitors : Prescribing
- Take 1 hour before sex (max 1 dose a day)
- if taken with food, onset of effect is delayed
Phosphodiesterase (type 5) inhibitors : Monitoring
- Review for therapeutic efficacy and SE
- Pulmonary hypertension - review regularly with a specialist
Phosphodiesterase (type 5) inhibitors : Patient Education
- Explain: drug will not produce an erection without sexual stimulation but only helps them have and maintain it.
5α-reductase inhibitors: Examples
Finasteride
5α-reductase inhibitors: Indications
BPH
- 2nd line after α-blockers
- improve LUTs (urinary retention, poor floor)
5α-reductase inhibitors: MOA
- 5α-reductase inhibitors reduce the size of the prostate gland.
- They do this by inhibiting the intracellular enzyme 5α-reductase, which converts testosterone to its more active metabolite dihydrotestosterone.
- As dihydrotestosterone stimulates prostatic growth, inhibition of its production by 5α-reductase inhibitors reduces prostatic enlargement and improves urinary flow.
- However, it can take several months for this effect to become evident clinically.
- For this reason, an α-blocker is usually preferred for initial therapy, with a 5α-reductase inhibitor added if the response is poor or if the prostate is particularly bulky.
5α-reductase inhibitors: Adverse Effects
- Impotence + reduced libido
- Gynaecomastia
- Hair growth
- Breast cancer
5α-reductase inhibitors: Contraindications
- Pregnant women
5α-reductase inhibitors: Interactions
None
5α-reductase inhibitors: Prescribing
- Oral
5α-reductase inhibitors: Monitoring
- Follow-up 3-6 months to review LUTs and SE
- Continue check-ups every 6-12 months while on treatment
5α-reductase inhibitors: Patient Education
- Main of treatment is to reduce the bulk of the prostate gland
- -> relive compression on the tube and easier to pass urine
- May take upto 6 months for symptoms to improve
- SE: less keen to have sex, inability to get or keep an erection
