Personal Details:

Name: Mr Peterson

Age: 50

Medical Record:

Past medical history: Oxybutynin 5 mg OD

Notes:

A 50-year-old man was prescribed oxybutynin for urinary frequency over a month ago.

As it wasn’t working, he doubled the dose himself. For the last week, he felt confused (noticed by his daughter). He stopped the medicine 3 days ago, and the confusion is better, but he has now developed diarrhoea.

Task:

1. Talk to the patient and take a focused history.

2. Address his concern.

Opening Sentence: “Doctor, I’m in a bit of a mess.”

Open History (to give freely): “I took that medicine for my bladder. The tablets weren’t really helping with my waterworks, so I thought I’d try taking two instead of one. Over the last two weeks, my daughter said I was getting muddled up. I got scared and stopped the tablets completely three days ago. The confusion is gone, but now I’m rushing to the toilet with diarrhoea.”

ICE (Ideas, Concerns, Expectations):

Ideas: “I don’t know. Have I poisoned myself? Is the diarrhoea a bug, or is it related to the tablets?”

Concerns: “Why did the tablets make me confused? Why have I got diarrhoea now?

Expectation: “I want to understand what’s happened to me.”

How to Act: You are a sensible man who is bewildered by the sequence of events. You made a genuine mistake in increasing the dose.

More History (only if asked): You have no other medical conditions. You don’t smoke and drink only occasionally.

Social History: Lives with his wife and daughter.

Medication History: Confirm the drug (Oxybutynin), the prescribed dose, the dose he was actually taking, and when he stopped.

History of Symptoms: Clarify the timeline: when the confusion started and when the diarrhoea started in relation to stopping the drug.

Exclude Alternatives: Ask about other causes of diarrhoea (travel, diet, contacts with similar illness) and confusion (fever, head injury).

Explain the situation:

Thank you for explaining that so clearly. It sounds like a very confusing and worrying sequence of events, but I think we can explain everything that has happened. It is all related to the oxybutynin tablets and how they work.

Addressing and answering the patient’s ICE:

Let’s start with the confusion. Oxybutynin belongs to a class of drugs called anticholinergics. They work by relaxing the bladder muscle, but they can also have effects elsewhere in the body, including the brain. Confusion is a well-known side effect, especially in older people or at higher doses. By doubling the dose yourself, you unfortunately gave yourself an overdose and experienced this side effect. It’s very good that your daughter noticed and that you stopped the tablets.

Next Steps:

Now for the diarrhoea. This is also related to the tablets. The same anticholinergic effect that relaxes your bladder also slows down your bowel. While you were taking the high dose, your bowel was probably very sluggish. Now that you have stopped the tablets suddenly, your bowel has ‘woken up’ and is over-compensating, leading to what we call rebound diarrhoea. It’s not a stomach bug; it’s a withdrawal effect from the medication.

Self-help measures if relevant:

The diarrhoea should settle down by itself over the next few days as your body readjusts. The most important thing is to drink plenty of fluids to avoid getting dehydrated.

Once this has all settled down, we need to revisit the original problem of your urinary frequency and find a different treatment that suits you better. There are other types of medication we can try. (mirabegron, tolterodine)

The management is explanation and advice. 1. Explain the mechanism of the side effects. 2. Advise on managing the self-limiting diarrhoea (oral fluids). 3. Provide important education about medication adherence and the danger of altering doses. 4. Arrange a follow-up appointment to address the original clinical problem (urinary frequency) once the acute issues have resolved.

What is scenario testing? This case tests the candidate’s knowledge of pharmacology, specifically the anticholinergic side effects of drugs like oxybutynin and the concept of rebound phenomena. The communication challenge is to explain these complex concepts to a patient in a simple, non-judgmental way, and to use the event as a teachable moment about medication safety.