Bahagian Amalan dan Perkembangan Farmasi (BAPF), KKM x The Malaysian Medical Gazette Series
Anticoagulants (often referred to as blood thinners) keep blood clots from forming in the blood vessels and may prevent existing clots from enlarging. It has been shown that anticoagulants are effective in the prevention and treatment of deep vein thrombosis, pulmonary embolism, and stroke in patients with atrial fibrillation (a type of arrhythmia – the heart beats at an irregular rhythm).
There are two main groups of oral anticoagulants. One of the anticoagulant classes includes vitamin K antagonists, such as warfarin. The second group consists of non-vitamin K antagonists. This group of anticoagulants is also known as direct oral anticoagulants.
Factors to be considered when taking warfarin
Warfarin has been approved since 1954 for preventing and treating blood clots. However, warfarin requires close and frequent blood monitoring of the International Normalized Ratio (INR), which is a measurement of how thin the blood is. Patients taking warfarin will always be subject to routine INR monitoring, and its readings should fall within the specified range. Appropriate INR values are essential to ensure the efficacy of warfarin and prevent the likelihood of bleeding.
Besides, INR levels are affected by dietary intake, as foods with high vitamin K content reduce the effectiveness of warfarin. Patients on warfarin need to watch their intake of vegetables with high levels of vitamin K in order to avoid the interaction of this vitamin with warfarin.
Direct Oral Anticoagulants (DOACs)
DOACs is a newer class of anticoagulants that act as alternatives to warfarin and may be more convenient for patients. There are currently four DOACs registered in Malaysia and available on the market. They are dabigatran, edoxaban, apixaban, and rivaroxaban.
In general, DOACs are safer and more effective than warfarin. They do not require frequent blood monitoring and can be given safely in fixed doses. Patients taking DOACs do not need to control their food intake. DOACs are also considered to have fewer drug interactions and act more rapidly than warfarin.
DOACs should be taken in accordance with the recommended dosage. Dabigatran and apixaban usually need to be taken twice daily, either before or after meals, at the same time each day. Rivaroxaban, on the other hand, should be taken once daily, promptly after a meal, to maximise its efficacy (effectiveness of the drug).
Evaluation of doctors in selecting anticoagulants for patients
The selection of an anticoagulant is mainly based on a doctor’s evaluation. Several factors, which include kidney function, other medications taken, bleeding history and risk, age, medication compliance, cost, and the need for other types of blood thinners, will be evaluated first. This evaluation can ensure that the patient receives appropriate and optimal treatment.
Advice for patients
- Patients should not modify the DOACs’ dose or stop taking them without medical advice by a doctor. Stopping DOACs without proper reasons could increase the risk of stroke or other blood clotting risks.
- Patients should tell doctors, dentists, or pharmacists that they are taking DOACs when attending appointment visits, prior to any surgery or dental procedures, or when purchasing any medicines. Patients have to inform the doctor or pharmacist if they are or plan to be pregnant or are breastfeeding. Always direct any inquiries or doubts to any healthcare provider to ensure accurate and correct answers are given. Plus, it is highly advisable for patients to be alert for important appointment dates and not miss any of them.
- Bleeding is a risk for anyone on anticoagulants. Always monitor for any signs and symptoms of bleeding, such as sudden bruises, gum or nose bleeding, abdominal pain or stomach discomfort, and prolonged or severe bleeding during menses. If necessary, patients are advised to seek medical advice when these conditions remain unresolved or worsen over time. Patients should also inform the healthcare provider immediately if they find their urine turning red or dark brown or their stools turning red, dark brown, or black.
- For proper storage, the DOAC, particularly dabigatran, must be kept in the original blister packs to protect it from moisture. These medications should not be transferred into pill boxes. Ensure to remove only one capsule from the blister pack at the time of use to preserve its stability and eventually its effectiveness.
If there are any inquiries regarding medicines, please call the National Pharmacy Call Centre (NPCC) at the toll-free number 1-800-88-6722 during weekdays from 8 a.m. to 5 p.m., except on public holidays.
This article is written by Karen Wee Lee Fang (Pharmacist), Hospital Tuanku Fauziah as part of the Bahagian Amalan dan Perkembangan Farmasi (BAPF), KKM x The Malaysian Medical Gazette Series to increase public awareness regarding important issues surrounding medications.
References
- Atrial Fibrillation and New Oral Anticoagulant Drugs – FDA.
- What is Venous Thromboembolism? – CDC.
- Deep Vein Thrombosis & Pulmonary Embolism – Chapter 8 – 2020 Yellow Book.
- What are Direct- Acting Oral Anticoagulants (DOACs)? Getting to the Heart of Stroke. American Heart Association.
- Position Paper on The Safety/Efficacy Profile of Direct Oral Anticoagulants in Patients with Chronic Kidney Disease. Concensus Document from the SIN, FCSA and SISET.
- Formulari Ubat KKM.
- DOAC Checklist, ACMTAC Protocol 2020.