Urology

Question 1

Oxybutinin, tolterodine

Answer 1

= antimuscarinics
Use: overactive bladder
MOA: bind to muscarinic (M3) receptors in the bladder, where they are competitive inhibitors of ACh. This promotes bladder relaxation, increasing bladder capacity and reducing urinary freq/urgency/urge continence.
Adverse effects: dry mouth, tachycardia, constipation, blurred vision
Cautions: contraindicated in UTI. Neuro side effects (drowsiness and confusion) are problematic in elderly patients with dementia. Use with caution in patients susceptible to angle-closure glaucoma (can increase intraocular pressure) and those at risk of arrhythmias or urinary retention
Interactions: adverse effects are more pronounced when prescribed with other antimuscarinics e.g. TCAs

Question 2

Doxazosin, tamsulosin

Answer 2

= alpha-1 adrenoceptor antagonists
Use: BPH, as an add-on in treatment-resistant HTN
MOA: block alpha-1 adrenoceptors which are found in SM (incl. BVs and the urinary tract), inducing relaxation. Vasodilation, a fall in BP, and reduced resistance to bladder outflow results.
Adverse effects: postural hypotension, dizziness, syncope (esp. after first dose)
Cautions: avoid in those with postural hypotension
Interactions: be wary of other BP lowering meds

Question 3

Dutasteride, finasteride

Answer 3

= 5 alpha reductase inhibitors
Use: BPH (second-line after alpha blockers) as they improve LUTS (urinary retention, poor urinary flow) and reduce the need for prostate surgery
MOA: inhibit the IC enzyme 5 alpha reductase (this converts testosterone to DHT), reducing prostatic enlargement and improving urinary flow. Can take several months to take effect.
Adverse effects: impotence, reduced libido, gynaecomastia, inhibition of hair growth, breast cancer
Cautions: pregnancy (reduce exposure, e.g. via semen)
Interactions: none

Question 4

Sildenafil, tadalafil

Answer 4

= phosphodiesterase type 5 inhibitors
Use: erectile dysfunction, primary pulmonary HTN
MOA: inhibits PDE-5 (predominantly in the SM of the corpus cavernous of the penis and there arteries of the lung) which increases cGMP concentrations (as PDE-5 usually breaks this down). This improves penile BF and erection quality. Needs sexual stimulation for an erection.
Adverse effects: flushing, headache, dizziness and nasal congestion (due to vasodilator effects). Hypotension, tachycardia and palpitations may occur, increased risk of vascular events.
Cautions: do not prescribe in patients with recent stroke or ACS, or hx of CVD. Avoided in hepatic or renal impairment.
Interactions: nitrates and nicorandil (these also increase NO conc). Prescribe in caution with vasodilators (alpha blockers and CCBs) as increased risk of hypotension. Conc and adverse effects of sildenafil are increased by cytochrome P450 inhibitors (amiodarone, diltiazem, fluconazole).

Question 5

Alprostadil

Answer 5

Use: erectile dysfunction
MOA: vasodilation
Adverse effects: haemorrhage, muscle spasms, penile disorder, sexual dysfunction, skin reactions, dizziness, headache, hypotension
Cautions: anatomical deformations of penis, priapism, RFs for CVD or cerebrovascular disorder. Do not use in patients with penile implants
Interactions: do not use with other agents for erectile dysfunction