Dr Sharon Rees @reesprescribe
Day 1: #oxybutynin is an anti-muscarinic drug approved in 1970s for incontinence & overactive bladder. #oxybutynin remains a 1st-line drug in UK. Side effects, especially dry mouth can lead to stoppage because immediate release (i.r) tablets can cause high levels of an active metabolite. Modified release (m.r) tablets/patches improve side-effects & concordance
Dr Sharon Rees @reesprescribe
Day 2: #oxybutynin is indicated for overactive bladder & neurogenic bladder from age 5 in UK. Dose age related. Adult i.r 5mg 2-3/day;can increase to x4/day. Modified release tablets available, oral solution, & transdermal patches (adults only).
Dr Sharon Rees @reesprescribe
Day 3: i.r fast oral absorption, low bioavailability, increased with food. High 1st pass metabolism & liver CYP3A4 breakdown produces an active metabolite. This peak > anti-muscarinic SEs. M.r > stable levels & patches bypass liver metabolism;both improve tolerance. Clearance primarily hepatic. T½ ~2hrs; prolonged in elderly
Dr Sharon Rees @reesprescribe
Day 4: #oxybutynin competitively inhibits acetylcholine (ACh) action on M1,2,3 receptors. Blocking ACh causes relaxation of bladder smooth muscle, increased capacity & reduced urgency/frequency. #oxybutynin has selectivity for M1 & 3, so high impact on salivary secretion (M1 receptor). Can take weeks to work while the bladder adapts
Dr Sharon Rees @reesprescribe
Day 5: ADEs. Confusion, GI disorders, blurred vision, dry eyes/mouth, urinary retention. Rare/not known; UTI, psychiatric disorders, convulsions, arrythmias, heat stroke. Contra-indicated if anti-muscarinic effect could worsen existing condition. Extremes of age more sensitive to anti-muscarinic effects; on STOPP list for elderly
Dr Sharon Rees @reesprescribe
Day 6: #oxybutynin drug-drug interactions; all drugs with anti-cholinergic effects (note high anti-cholinergic burden score). 2 ‘severe’ theoretical DDIs; clozapine re constipation/intestinal obstruction) & zonisamide (overheating/dehydration). CYP3A4 inhibitors eg itraconazole can increase exposure
Dr Sharon Rees @reesprescribe
Day 7: Other uses for #oxybutynin may be trialled in the future i.e for hyperhidrosis, hot flushes & sleep apnoea
Earn your CPD certificate
With the help of Prescribing and Therapeutics Training Ltd and the Journal of Prescribing Practice, you can earn your 1-hour CPD certificate
In addition to the posts, read the BNF treatment summary on urinary incontinence and pelvic organ prolapse in women, as well as the monograph on oxybutynin. Another useful source is the Summary of Product Characteristics for oxybutynin (here oral) – see links below. Once you have completed this, answer the 10 questions. Submit your answers to reesprescribe@gmail.com. If you answer at least eight out of 10 questions correctly, you will receive your CPD certificate via email.
Further reading on #oxybutynin
- https://bnf.nice.org.uk/treatment-summaries/urinary-incontinence-and-pelvic-organ-prolapse-in-women/
- https://bnf.nice.org.uk/drugs/oxybutyninhydrochloride
- https://www.medicines.org.uk/emc/product/14310/smpc#gref
- Oxybutynin is used for adults and children TRUE or FALSE?
- Which of the following is TRUE?
- Oxybutynin is broken down by a major liver enzyme group, CYP3A4
- Oxybutynin is water loving and stays mainly in the plasma
- Oral oxybutynin has high bioavailability
- Oral oxybutynin undergoes minimal first pass metabolism
- Patch delivery can improve tolerance TRUE or FALSE?
- Oxybutynin is a first-line drug for urinary urgency and frequency TRUE or FALSE?
- Oxybutynin has weak anti-muscarinic properties TRUE or FALSE?
- Which of the following is FALSE?
- Oxybutynin acts on muscarinic receptors type 1, 2 and 3
- Oxybutynin relaxes the bladder smooth muscle
- Oxybutynin can help smooth muscle spasms
- Oxybutynin has its primary action on M2 receptors
- Oxybutynin has an active metabolite which opposes M1 activity TRUE or FALSE?
- Oxybutynin is on the STOPP list for the elderly TRUE or FALSE?
- Which of the following are common adverse drug effects for oxybutynin?
- Diarrhoea, insomnia, rash
- Pruritis, anaemia, seizure
- Dry mouth, constipation, agitation
- Oedema, hypoglycaemia, weight loss
- Oxybutynin scores a 3 (highest) using the anti-cholinergic burden scoring system ‘ABC calculator’* TRUE or FALSE? *https://www.acbcalc.com