4th March 2024

A 63-year-old lady is admitted to the ward with an infective exacerbation of COPD.

A 63-year-old lady is admitted to the ward with an infective exacerbation of COPD. She has a past medical history of COPD, hypertension, mild depression, eczema and previous DVTs. During the patient’s stay in hospital, she has another DVT. On review, her INR is 1.5 despite taking her warfarin daily. Her current medications are as follows:

DATE	DRUG NAME	DOSE	ROUTE	FREQUENCY	SIGNED
15/05/2023	WARFARIN	6mg	ORAL	ONCE DAILY	DR
15/05/2023	ST JOHN’S WORT	425mg	ORAL	ONCE DAILY	DR
15/05/2023	SALBUTAMOL	200mcg	INHALED	PRN	DR
15/05/2023	LISINOPRIL	20mg	ORAL	ONCE DAILY	DR
15/05/2023	AMLODIPINE	10mg	ORAL	ONCE DAILY	DR
15/05/2023	BECLOMETHASONE DIPROPIONATE	400mcg	INHALED	TWICE DAILY	DR
15/05/2023	CARBOCISTEINE	0.5g	ORAL	THREE TIMES DAILY	DR
15/05/2023	HYDROMOL	ON AFFECTED AREAS	TOPICAL	PRN	DR

Select the most likely drug that has caused her INR to be low.

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