Direct oral anticoagulant (DOACs), such as rivaroxaban and apixaban, are under- or over-prescribed in up to one in eight patents, finds a new study. These prescribing issues can have life threatening consequences, and they most often occur after a provider writes the initial prescription, according to a Michigan Medicine-led study in Thrombosis and Haemostasis.
“Direct oral anticoagulants may be viewed as simpler to manage than traditional blood thinners, like warfarin, but our results highlight why providers need to be consistently monitoring anticoagulant medications before a patient experiences thrombotic or bleeding harms,” said Geoffrey Barnes, MD, MSc, senior author and associate professor of cardiology-internal medicine at U-M Medical School.
At hospitals across Michigan, off-label dosing of DOACs was relatively common among patients being treated for atrial fibrillation and venous thromboembolism, when blood clots form in the veins.
Researchers evaluated five years of prescribing data from 2018–2022 through the Michigan Anticoagulant Improvement Initiative, a statewide quality improvement collaborative funded by Blue Cross Blue Shield and Blue Care Network of Michigan.
Nearly 70% of the alerts to off-label dosing occurred during a follow up visit compared to the time of the initial prescription, according to the study results
When prescribers were contacted about the dosing issue, they made changes three-quarters of the time.
However, only 18% of dosing alerts resulted in contact to a prescriber.
“While many clinical decision support tools are designed to ensure accurate medication dosing at the time of an initial prescription, few address the need for ongoing monitoring,” said first author Grace C. Herron, a fourth-year student at U-M Medical School.
“Any health system that aims to improve safe and effective DOAC prescribing must address the ongoing prescribing period which can last months to years.”
Direct oral anticoagulants became available in 2010 and quickly gained popularity because, unlike conventional blood thinners, they do not require routine monitoring to test their effectiveness.
However, these medications have their own complicated dosing schemes that can vary based on factors such as kidney function and select interactions between drugs.
“The hospital systems in the Michigan Anticoagulation Quality Improvement Initiative are leading national efforts to develop, implement and test anticoagulation stewardship teams that ensure patients are always receiving the safest and most appropriate blood thinner possible,” Barnes said.
“The nurses and pharmacists on these teams play a critical role in helping to monitor for any prescription issue that might develop, even months or years after a patient starts on a blood thinner medication.”
June Bellamy’s 83-year-old mother got COVID in March 2022 and was in intensive care for two weeks. She was diagnosed with heart disease. When she was discharged, she was put on oxygen and prescribed medication, including blood-thinning tablets containing rivaroxaban.
During a visit to the doctor earlier this month, Bellamy and her mother were shown a list of different medications containing rivaroxaban. But when they tried to obtain the generic version at the dispensary, which is about 40% cheaper, the supervisor said that because of an ongoing court case they were not allowed to supply it anymore.
“We’ve had to buy the expensive one,” says Johannesburg resident Bellamy, who has been unemployed since 2017. It costs her R1100 a month and she also has to buy other medications. She says her mother is on a basic medical aid plan and the medication is not covered.
“While I’m financially decimated, I’m trying to do what I can,” said Bellamy.
One year and counting
There are a number of court cases dealing with the issue. One of these is between Bayer and Clicks and was heard in the court of the commissioner of patents in Gauteng. The details are complicated and we explain them below. But what is clear is that in April 2022 Judge Colleen Collis reserved judgment in this urgent matter about the sale of blood-thinning tablets. More than a year later, she has failed to hand down her ruling.
In urgent matters judgment is expected almost immediately. It is astonishing for a judge to take a year over any judgment, let alone an urgent one. The judicial norms and standards state that judgments, in non-urgent matters, should be handed down within three months of being reserved.
GroundUp previously reported that the last available list of late judgments on the judiciary’s website is 31 December 2021. The judiciary has stonewalled our requests for an updated list.
We asked for comment from Chief Justice Raymond Zondo and Judge Collis but received no response.
What the case is about
The case deals with the extension of Bayer’s patent on rivaroxaban from December 2020 to January 2026.
In 2000, Bayer obtained a patent on rivaroxaban. Patents are granted for 20 years and so the patent was to expire in December 2020.
The patent-holder of a medicine, in this case Bayer, has exclusive control over it. No other pharmaceutical company may sell the medicine in South Africa during the patent period, at least not without Bayer’s permission. Effectively a patent holder has a monopoly. The point of patents is to create an incentive for pharmaceutical companies to develop new medicines.
In 2007 Bayer obtained a patent for rivaroxaban to be dosed once daily (the original patent was silent on dosing). This extended the patent to 19 January 2026. This kind of patent extension is widely criticised by health activists and is called evergreening.
After the initial patent expired in December 2020, two pharmaceutical companies, Austell and Dr Reddy’s, launched generic versions of rivaroxaban. To cut a long story short, there followed a series of court actions which resulted in Austell and Dr Reddy’s being interdicted from selling their versions of rivaroxaban in South Africa. But the interdicts did not yet stop the big three pharmacy groups, Dis-Chem, Alpha Pharm and Clicks, selling the stock they had of both generic products.
Dis-Chem and Alpha Pharm reached a settlement with Bayer in respect of Dr Reddy’s product, Rivaxored, but Clicks did not. Bayer applied to the court of the commissioner of patents to interdict Clicks from selling rivaroxaban and obtained an urgent interim interdict in March 2022. Shortly after that, in April 2022, the main (and still urgent) hearing for this application took place and Judge Collis reserved judgment. That is where matters stand, over a year later.
As of 13 May, OpenUp’s medicine price website gives the price of a pack of 42 Xarelto (Bayer’s rivaroxaban product) 15mg tablets as R1532. Austell’s equivalent product, Rezalto, is R931.26. Dr Reddy’s product, Rivaxored, is a little higher priced than Rezalto (at 15mg) but considerably lower than Bayer. There’s also iXarola, Bayer’s “authorised generic”, which they brought to market just before the expiry of the 2000 patent. It’s priced at R1285. (These prices exclude the dispensing fee.)
The timeline below contains more detail.
Timeline
2000: Bayer gets patent for rivaroxaban (expires December 2020).
2007: Bayer gets patent for dosing rivaroxaban once daily instead of twice daily (effectively means that the patent expires on 19 January 2026).
2020, December: Initial patent expires.
2021, January: Austell launches its generic version of rivaroxaban, called Rezalto.
2021, April 1: Dr Reddy’s launches its generic version of rivaroxaban, called Rivaxored.
2021, May: Bayer obtains urgent interdicts that stop Austell from selling Rezalto.
2021, December: Bayer obtains interim interdict against Dr Reddy’s, but the interdict does not extend to stopping pharmacies from selling the stock they already had of Dr Reddy’s generic pills.
2022, January: Bayer then launches another urgent application to interdict three pharmacy groups from selling Dr Reddy’s generic pills still in stock. Dis-Chem and Alpha Pharm reach a settlement with Bayer. But Clicks refuses to settle and opposes Bayer’s application.
2022, March 15: Bayer obtains an urgent interim interdict against Clicks at the court of the commissioner of patents in Gauteng, pending a main hearing which takes place at the same court in April.
2022, April: The urgent interdict application between Bayer and Clicks is heard by Judge Colleen Collis in the court of the commissioner of patents in Gauteng. Collis reserves judgment.
2023, May: Judgment has still not been handed down by Judge Collis.
The anticoagulant drug heparin is widely given to patients with blood clotting disorders or after surgery to prevent complications. But it remains difficult to dose correctly, potentially leading to overdosing or underdosing. A team of Penn State researchers combined heparin with a protein fragment, peptide, to slow down the release of the drug and convey the medication directly to the site of a clot. They published their findings in the journal Small.
“We wanted to develop a material that can gradually deliver heparin over time rather than the current iteration that gets cleared from the body in a couple of hours,” said corresponding author Scott Medina, Penn State associate professor of biomedical engineering. “We also wanted to deliver the drug through the skin instead of through an IV.”
When mixed, positively charged peptides and negatively charged heparin bind to create a nanogranular paste that can be injected under the skin, forming a cache of material that is then diffused in the circulatory system and travels to blood clots when they appear. The turbulent flow of fluid near a blood clot triggers the two materials to separate, allowing heparin to begin its anticoagulating action.
“The peptide is ideal for pairing with heparin because it essentially blocks heparin’s action until it is needed in the body,” said Atip Lawanprasert, doctoral student in biomedical engineering and first author on the paper. “The peptide also has some anticoagulating properties on its own: It binds to platelets in the blood, enabling action at the clotting site.”
Without an added bonding agent, heparin applies its anti-clotting properties indiscriminately, not just at blood clot sites, and clears quickly, its half-life only 60 to 90 minutes. Using preclinical animal trials, researchers determined that the addition of peptide allows for a dramatic increase of heparin’s half-life, to up to nearly 24 hours.
“The peptide increases heparin’s effects by more than ten times longer than what is currently being used,” Medina said. “The increased half-life allows for sustained treatments for patients, less medication waste and more accurate dosing. Eventually, this could allow the medication to be injected under the skin just once a day, rather than an all-day IV drip.”
Next, researchers plan to replicate the study in a clinical setting, as well as study the effect of the medication’s toxicity with multi-day administration.
A major UK-wide trial has found that the the oral anticoagulant apixaban does not help patients recovering from moderate and severe COVID compared to standard care – despite this approach being offered to patients.
To date, more than a thousand NHS patients hospitalised with COVID have taken part in HEAL-COVID, a platform trial that is aiming to find treatments to reduce the number who die or are readmitted following their time in hospital.
The trial’s preliminary results have shown that prescribing the oral anticoagulant Apixaban does not affect subsequent mortality or rehospitalisation of COVID over the following year (apixaban 29.1%, versus standard care 30.8%).
As well as being ineffective, anticoagulant therapy has known serious side effects, and these were experienced by participants in the trial with a small number of the 402 participants receiving apixaban discontinuing due to bleeding events.
There was also no benefit from Apixaban in terms of the number of days alive and out of hospital at day 60 after randomisation (apixaban 59 days, versus standard care 59 days).
Following these results, the trial will continue to test atorvastatin, which acts on other mechanisms of disease that are thought to be important in COVID.
Chief Investigator for the trial Professor Charlotte Summers is an intensive care specialist at Addenbrooke’s Hospital and the University of Cambridge. She said: “These first findings from HEAL-COVID show us that a blood thinning drug, commonly thought to be a useful intervention in the post-hospital phase is actually ineffective at stopping people dying or being readmitted to hospital. This finding is important because it will prevent unnecessary harm occurring to people for no benefit. It also means we must continue our search for therapies that improve longer term recovery for this devastating disease.”
HEAL-COVID enrols patients when they are discharged from hospital, following their first admission for COVID. They are randomised to a treatment and their progress tracked.
Nirmatrelvir-ritonavir (Paxlovid) is often given to heart disease patients with symptomatic COVID to prevent progression to severe disease – but it can interact with some previously prescribed medications. A review paper published in the Journal of the American College of Cardiology examines the potential drug-drug interactions (DDIs) between Paxlovid and commonly used cardiovascular medications, as well as potential options to mitigate severe adverse effects.
“Awareness of the presence of drug-drug interactions of Paxlovid with common cardiovascular drugs is key. System-level interventions by integrating drug-drug interactions into electronic medical records could help avoid related adverse events,” said Sarju Ganatra, MD, senior author of the review.
He continued: “The prescription of Paxlovid could be incorporated into an order set, which allows physicians, whether it be primary care physicians or cardiology providers, to consciously rule out any contraindications to the co-administration of Paxlovid. Consultation with other members of the health care team, particularly pharmacists, can prove to be extremely valuable. However, a health care provider’s fundamental understanding of the drug-drug interactions with cardiovascular medications is key.”
In December 2021, Paxlovid received emergency use authorisation from the US Food and Drug Administration as an oral antiviral agent for the treatment of symptomatic, non-hospitalised adults with mild to moderate COVID infection who are at high risk for progression to severe disease. Patients with heart disease and other risk factors, including diabetes, high blood pressure, chronic kidney disease and smoking make up a large portion of the high-risk population for whom Paxlovid is beneficial.
According to the authors, Paxlovid has been shown to be very effective in patients with existing heart disease, but it has significant DDIs with commonly used cardiovascular medications, highlighting the importance for all clinicians to be familiar with these DDIs. As there is limited clinical information regarding DDI-related adverse events, the authors used existing knowledge and data regarding how therapies like Paxlovid typically react with other medications to provide guidance regarding potential interactions and the associated likely consequences based on the degree of interaction.
The review provides an in-depth overview of a variety of cardiovascular medications used to treat many forms of heart disease. Five of the most important cardiovascular drug interactions with Paxlovid to be aware of include:
Anti-arrhythmic agents
Many anti-arrhythmic agents are metabolised in a way that increases plasma levels when co-administered with Paxlovid. While it may be possible to start Paxlovid after 2–2.5-day temporary discontinuation of the anti-arrhythmic agents, this may not be feasible from a practical standpoint. Clinicians are advised to consider alternative COVID therapies and avoid co-administration of these agents with Paxlovid. Sotalol, another anti-arrhythmic agent, is renally cleared and does not interact with Paxlovid.
Antiplatelet agents and anticoagulants
Antiplatelet agents are used for the treatment of coronary artery disease, particularly if a patient has received a stent. Aspirin and prasugrel are safe to co-administer with Paxlovid. There is an increased risk of blood clots when Paxlovid is given alongside clopidogrel and an increased risk of bleeding when given with ticagrelor. When possible, these agents should be switched to prasugrel. If patients have contraindication to taking prasugrel, then co-administration of Paxlovid should be avoided and alternative COVID therapies should be considered.
Anticoagulants such as warfarin may be co-administered with Paxlovid but require close monitoring of clotting factors in bloodwork. The plasma levels of all direct oral anticoagulants increase when co-administered with Paxlovid, therefore dose adjustment or temporary discontinuation and use of alternative anticoagulants may be required.
Certain statins
Co-administration of simvastatin or lovastatin with Paxlovid can lead to increased plasma levels and subsequent myopathy and rhabdomyolysis, a condition in which the breakdown of muscle tissue releases a damaging protein into the bloodstream. These agents should be stopped prior to initiation of Paxlovid. A dose reduction of atorvastatin and rosuvastatin is reasonable when co-administered with Paxlovid. The other statins are considered safe when given along with Paxlovid.
Ranolazine
Plasma concentration of ranolazine, used to treat angina and other heart-related chest pain, is exponentially increased in the presence of CPY450 inhibitors like Paxlovid, thereby increasing the risk of clinically significant QT prolongation and torsade de pointes (a type of arrhythmia). Co-administration of Paxlovid is therefore contraindicated. Temporary discontinuation of ranolazine is advised if prescribing Paxlovid.
Immunosuppressive agents
The plasma levels of immunosuppressive agents prescribed for patients who have undergone heart transplantation exponentially rise to toxic levels when co-administered with Paxlovid. Temporary reduction of dosing of immunosuppressive agents would require frequent monitoring and be logistically difficult. Therefore, alternative COVID therapies should be considered in these patients.
The authors conclude awareness and availability of other COVID therapies enable clinicians to offer alternative treatment options to patients who are unable to take Paxlovid due to DDIs.
A new biomolecular anticoagulant platform reported in Nano Letters holds promise as a revolutionary advancement over the anticoagulants currently used during surgeries and other procedures. The technology is based around injectable fibre structures which can be quickly dissolved and excreted by the kidneys.
“We envision the uses of our new anticoagulant platform would be during coronary artery bypass surgeries, kidney dialysis, and a variety of vascular, surgical and coronary interventions,” said Kirill Afonin, leader of the team which invented the technology. “We are now investigating if there are potential future applications with cancer treatments to prevent metastasis and also in addressing the needs of malaria, which can cause coagulation issues.”
The team’s technology turns to programmable RNA-DNA anticoagulant fibres that, when injected into the bloodstream, form into modular structures that communicate with thrombin. The technology allows the structures to prevent blood clotting as it is needed and then be quickly eliminated via the renal system once their job is done.
The fibre structures use aptamers, short sequences of DNA or RNA designed to specifically bind and inactivate thrombin.
“Instead of having a single small molecule that deactivates thrombin,” Afonin said, “we now have a relatively large structure that has hundreds of the aptamers on its surface that can bind to thrombin and deactivate them. And because the structure becomes larger, it will circulate in the bloodstream for a significantly longer time than traditional options.”
The extended circulation in the bloodstream allows for a single injection, instead of multiple doses. The design also decreases the concentration of anticoagulants in the blood, resulting in less stress on the body’s renal and other systems, Afonin said.
This technology also introduces a novel “kill-switch” mechanism, which reverses the fibre structure’s anticoagulant function with a second injection. This lets makes the fibres able to be metabolised into materials that are tiny, harmless, inactive and easily excreted by the renal system.
The entire process takes place outside the cell, through extracellular communication with the thrombin. The researchers note that this is important as immunological reactions do not appear to occur, based on their extensive studies.
The team has tested and validated the platform in computer models, human blood and various animal models. “We conducted proof-of-concept studies using freshly collected human blood from donors in the US and in Brazil to address a potential inter donor variability,” Afonin said.
The technology may provide a foundation for other biomedical applications that require communication via the extracellular environment in patients, he said. “Thrombin is just one potential application,” he said. “Whatever you want to deactivate extracellularly, without entering the cells, we believe you can. That potentially means that any blood protein, any cell surface receptors, maybe antibodies and toxins, are possible.”
The technique permits the design of structures of any shape desired, with the kill switch mechanism intact. “By changing the shape, we can have them go into different parts of the body, so we can change the distribution,” Afonin said. “It gets an extra layer of sophistication of what it can do.”
While the application is sophisticated, production of the structures is relatively easy. “The shelf life is amazingly good for these formulations,” Afonin said. “They’re very stable, so you can dry them, and we anticipate they will stay for years at ambient temperatures, which makes them very accessible to economically challenged areas of the world.”
COVID patients in intensive care units (ICU) receiving full-dose anticoagulants are significantly more likely to experience heavy bleeding than patients prescribed a smaller yet equally effective dose, according to a recent study.
The research, which compared the safety and effectiveness of blood clot treatment strategies for more than 150 critically ill COVID patients at two hospitals, found that almost all patients who experienced significant bleeding were on mechanically ventilation and receiving full-dose anticoagulants.
The results, published last month in Hospital Pharmacy, may inform treatment guidelines for blood clots in hospitalised COVID patients, who are at an increased risk for both blood clots and severe bleeding. Previous reports have found that 17% of hospitalised COVID patients experience blood clots, said first author Maya Chilbert, PharmD, clinical assistant professor in the UB School of Pharmacy and Pharmaceutical Sciences.
“A wide variety of practice exists when it comes to approaching blood clots in hospitalized patients with COVID, and there is little data to suggest improved outcomes using one strategy versus another,” said Chilbert. “Caution should be used in mechanically ventilated patients with COVID when selecting a regimen to treat blood clots, and the decision to use full-dose blood thinners should be based on a compelling indication rather than lab markers alone.”
The study analysed the outcome of blood clot treatments and the rate of bleeding events for more than 150 patients with COVID-19 who received either of two blood thinner regimens: a full-dose based on patient levels of D-dimer, and the other a smaller but higher-than-standard dosage.
Patients’ average age was 58, and all experienced elevated levels of D-dimer, fibrinogen, and prothrombin time.
Significant bleeding events were experienced by almost 14% of patients receiving full-dose anticoagulants, compared to only 3% of patients who received a higher-than-standard dosage. All patients who experienced bleeding events were on mechanical ventilation. No difference was reported in the regimens’ effectiveness at treating blood clots. Further investigation is needed to determine the optimal strategy for treating blood clots and bleeding in hospitalised COVID patients, said Asst Prof Chilbert.
A novel study has isolated powerful anticoagulants from the saliva of ticks, which may have reduced potential for bleeding.
Blood-feeding animals rely on specific molecules in their saliva to overcome defence mechanisms of their mammalian hosts for successful survival. The saliva of ticks, for example, contains molecules that can prevent blood from clotting, and which can also suppress inflammation or immune response to enable continuous feeding on the same bite site for days, sometimes undetected by the host. The harmful effects of these parasites can actually be harnessed for medical treatments.
In their paper, published in Nature Communications, the authors explain how the cardiovascular team developed a series of thrombin inhibitors to be potent anticoagulants based on sequences of inhibitors of blood coagulation enzyme thrombin found in the tropical bont tick Amblyomma variegatum.
The team developed a series of thrombin inhibitors to be powerful anticoagulants.
Anticoagulants are used in conditions where there is an increased propensity to form blood clots in our body depriving blood supplies to important tissues and organs, otherwise known as thrombosis. These drugs are needed in many diseases caused by blood clots including heart attacks, strokes, deep vein thrombosis, pulmonary embolism and even some severe complications caused by SARS-CoV-2 infection.
These next-generation anticoagulants will now need to be tested in human trials to determine if they can effectively counteract clotting without the bleeding side effects of currently available anticoagulants.
If treated with therapeutic-dose anticoagulation, moderately ill patients hospitalised with COVID have better odds of survival, according to an international study published in The New England Journal of Medicine.
COVID patients frequently develop a pro-coagulative state caused by virus-induced endothelial dysfunction, cytokine storm and complement cascade hyperactivation. Thrombotic risk appears directly related to disease severity and worsens patients’ prognosis.
Moderately ill COVID patients treated with therapeutic-dose anticoagulation with unfractionated or low molecular-weight heparin were 27% less likely to need cardiovascular respiratory organ support such as intubation, said Ambarish Pandey, MD, Assistant Professor of Internal Medicine at UT Southwestern, who served as site investigator and . Moderately ill patients had a 4% increased chance of survival until discharge without requiring organ support with anticoagulants, according to the study involving 2200 patients.
“The 4% increase in survival to discharge without needing organ support represents a very meaningful clinical improvement in these patients,” said Dr Pandey, a Texas Health Resources Clinical Scholar specialising in preventive cardiology and heart failure with preserved ejection fraction. “If we treat 1,000 patients who are hospitalized with COVID with moderate illness, an additional 40 patients would have meaningful improvement in clinical status.”
Moderately ill patients were defined as those who did not need intensive care unit-level support. The participating platforms for the study, included Antithrombotic Therapy to Ameliorate Complications of COVID-19 (ATTACC); A Multicenter, Adaptive, Randomized Controlled Platform Trial of the Safety and Efficacy of Antithrombotic Strategies in Hospitalized Adults with COVID-19 (ACTIV-4a); and Randomized, Embedded, Multifactorial Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP).
A parallel study reported in The New England Journal of Medicine found however that therapeutic-dose anticoagulation did not help severely ill patients.
