PP+401+-+10

=Webster-pak containing warfarin, digoxin, perhexiline, HCT and alendronate=

//You are a locum who has been working at a rural community pharmacy the last few days. Earlier in the week you prepared a Webster-pak® for Mr Patrick Smith (68 years old) as follows://



Problem
Interaction between hydrochlorothiazide and digoxin: hypokalaemia causing digoxin toxicity Could be taking an OTC medication (St John's Wort) that could be interacting with their medications Patient has experienced drug interactions which increased warfarin/INR levels and presents with bleeding problems of some sort Check webster-pak for compliance

= =

Questions to Ask
//Patient returns webster pack and you find they have skipped alternate days of warfarin tablets// - I have noticed the warfarin is still in the packet, may i ask why you aren't taking them anymore? //they experienced unexplained bruising and heard from a friend that this can happen and that they got their dose lowered which is what the patient is trying to do (without doctor's input)// - When did the bruising happen? - Is there anything else that may be the cause of the bruise? //nothing that suggests injury to the area// - Check recent medications, diet, otc products, diseases to see what has changed INR - Have you started any OTC products or new medications (ginseng, garlic, gingko, St Johns Wort)? //no// - When did the doctor last check your INR? //a while ago, and will see the doctor again in 3 weeks//

What to do
- Although bruising is a common SE of warfarin, explain sudden stopping of warfarin is dangerous and make INR unstable, shouldn't change without doctor's supervision (especially important in this patient as he is at high risk of CV event) - Tell patient you will contact the GP for him to book an appointment and let the doctor know of the situation and to ask what actions should be taken (which dose of warfarin to take) - You can say that he may miss his 1mg dose again today as he has been doing, and then Dr may advise to miss the next dose as well (as the INR may still be climbing), but it is essential to get a level and the advice of the Dr. - Meanwhile offer the new webster pack with the warfarin removed. - Follow up is crucial

Over-anticoagulation increases the risk of haemorrhage. The first step in managing this problem is to identify the cause. Common causes include starting or stopping an interacting medication, deteriorating liver function, and patient error (such as taking the wrong dose or confusing different strength tablets). Many of these causes are preventable. The approach to a raised INR should be individualised, paying attention to the indication for the warfarin, the patient’s risk of bleeding and whether it is safe to continue therapy at all. Some patients need to be admitted to hospital, while others just need to miss a dose of warfarin.

Resources
[|Australian Prescriber: Managing warfarin in the community]