In this episode I’ll:
1. Discuss an article about using IVIG for refractory HIT.
2. Answer the drug information question “Do some quinolones have lower QTc prolongation risk than others?”
3. Share a resource for searching FDA reports of adverse reactions to medications.
Members of my Critical Care Pharmacy Academy will have access to my new Masterclass on vasopressor use in the ICU starting Thursday, October 5, 2017. To learn more about becoming a member of the Academy go to pharmacyjoe.com/academy.
Article
IVIg for Treatment of Severe Refractory Heparin-Induced Thrombocytopenia
Lead author: Anand Padmanabhan
Published in the journal CHEST September 2017
Background
Heparin-induced thrombocytopenia (HIT) is sometimes complicated by severe thrombocytopenia and thrombosis. Use of anticoagulants such as argatroban in severe HIT may increase bleeding risks. This is more likely in patients who have a prolonged course of the disease. Other than non-heparin anticoagulants, there are no other established therapies for severe HIT.
Methods
The authors describe three patients with HIT who had severe thromboembolism and prolonged thrombocytopenia refractory to standard treatment but who achieved an immediate and sustained response to intravenous immune globulin therapy (IVIG). Immunoassay testing was performed to investigate the mechanism of action of IVIG.
Results
A 47 year-old man with severe, persistent HIT, DVT, PE, atrial thrombus and platelets of 13,000/μL was then treated with 1 g/kg/d of IVIG on 2 consecutive days. Platelet counts increased to 55,000, 108,000, and 164,000/μL over the next 3 days.
A 73 year-old man with severe, persistent HIT, PE, and platelets of 25,000/μL was given IVIG 1 g/kg/d on 2 consecutive days. Platelet counts increased to 101,000/μL, 145,000/μL, and 177,000/μL over the next 3 days.
A 72 year-old man with severe, persistent HIT, DVT and platelets of 16,000/μL was given 2 doses of IVIG 1 g/kg 2 days apart. Platelet counts increased to > 50,000/μL and 100,000/μL, respectively, within 24 hours of each dose.
The authors found that IVIG inhibits HIT antibody-mediated platelet activation.
All three patients did well on long-term anticoagulation therapy with direct oral anticoagulants.
Conclusion
The authors concluded:
These studies suggest that IVIg treatment should be considered in patients with HIT who have severe disease that is refractory to standard therapies.
Discussion
Further research is needed before IVIG should be used routinely in patients with HIT. However, in patients with severe, prolonged HIT that appears refractory to standard treatment, IVIG may be of potential benefit. I would consider using the dose described in this case series of IVIG 1 gram per day for 2 consecutive days.
Drug information question
Q: Do some quinolones have lower QTc prolongation risk than others?
A: Yes.
Fluoroquinolones prolong the QT interval by blocking voltage-gated potassium channels, especially the rapid component of the delayed rectifier potassium current I Kr. Blockade of these channels and prolongation of QTc occurs in a dose dependent manner. However, the quinolones do not have equal potency when it comes to IKr blockade and QTc prolongation.
Of the commonly used quinolones, moxifloxacin has the highest risk of QTc prolongation. Levofloxacin has a lower risk of QTc prolongation than moxifloxacin, and ciprofloxacin has an even lower risk. For more on how I evaluate QTc related drug interactions, go to pharmacyjoe.com/episode12.
Resource
The resource for this episode is the FDA’s new user-friendly search tool that improves access to data on adverse events associated with drug and biologic products. This tool is available through the FDA’s Adverse Event Reporting System (FAERS). It has been designed to make it easier for the public to access adverse event information without having to file freedom of information requests.
I was easily able to search the database for adverse events related to medications. The database indicated whether or not an event was serious or fatal, and a general description of the reaction was provided. If you want the complete details of the reaction you will still need to file a freedom of information request with the FDA.
I think this database will be most useful for those doing Pharmacy & Therapeutics committee formulary presentations as a way to gather data on a medication to inform the P&T committee.
If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.
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