Ciprofloxacin prolongs half life of warfarin (it’s a p450 inhibitor) so raises INR (although studies fail to establish a predictable reaction).
All quinolone antibiotics (ciprofloxacin, levofloxacin, moxifloxacin etc) have reports of raised INR.
St Johns Wort is an enzyme inducer so can make warfarin less effective.
Mnemonics: Erections go up, Cobras will being you down!
Drugs that interact with warfarin to raise INR: (INR goes up – erections go up)
- Miconazole (and the other azoles)
- SSRIs (sertaline)
For all aged men sidenafil can cause erections
…floxacins, amiodarone, allopurion, miconaxole, ssris, cimetidine, clarithrimycin, ezetimide
Drugs that reduce INR – Enzyme inducers:
- Ocp/ hrt
- St. John’s wart
Carbimazole/carbamazepine, OCP/HRT, Barbituates, Rifampicin, Azothiaprine, St Johns Wort