Introduction

Thrombosis is when a blood clot forms in the blood vessels, and it can happen in veins or arteries. It is implicated in many illnesses like heart attacks, strokes, lung clots (pulmonary embolism), and limb ischemia. It is key to stop or treat thrombosis to make sure things like stents, fistulas, and grafts stay open. A variety of treatment options are available in order to treat these blood clots.

Clots in the body's blood vessels are a top cause of sickness and death across the globe. The worst thing that can happen when you have heparin-induced thrombocytopenia is getting a clot. Drugs that stop clotting are key in stopping and treating thrombosis.¹¹ Heparin, a common anticoagulant, has worked well in many health cases with its use increasing during the COVID-19 crisis.^4,3

Now, DOACs are often picked first to reduce strokes from atrial fibrillation and to treat clot issues in deep veins and lungs.¹⁰ Patients still use oral warfarin a lot. It works well to stop and treat clots and lower the risk.⁹

Heparin

Heparin is the first blood-thinning drug used in health care. It is a naturally occurring polysaccharide belonging to the family of glycosaminoglycans (GAG) which is present in mast cells. Unfractionated heparin (UFH) is the least processed form of the natural GAG produced via purification from animal tissue, most commonly porcine intestine.^3,4 Most of this heparin is currently obtained from animal tissue under less than ideal current good manufacturing practice (cGMP) conditions.⁴ Even though low-weight heparin (LMWH) has now taken over from UFH (unframed heparin) in most cases, UFH is still the top choice for those who have heart-lung machine (CPB) surgery.

Anti-coagulating properties

Along with its blood-thinning effect heparin can also reduce swelling, slow cell growth, and block other body reactions.³

The blood-thinning effect of LMWH is steadier than that of UFH. Heparin facilitates blood loss from the microvasculature and can increase bleeding duration in people.

Non-anticoagulant Activities of Heparin

Includes anti-inflammatory activity, anti-tumour property, and anticomplement effects.³

Heparin reduces inflammation by a number of methods, including as blocking adhesion molecules and heparinase, which are both involved in the recruitment of leukocytes into tissues and the neutralisation of cationic mediators.² The primary mechanism by which heparin helps prevent early miscarriage is the inhibition of placental thrombosis.³ Growth factor binding to the cell surface, decreased bone osteoblast activity, increased risk of osteoporosis, and antiproliferative actions, such as blocking the growth of smooth muscle cells and endothelial cells.^3,5

Dosage

Initial dosing of IV heparin for venous thromboembolism is weight-based. Each patient responds to heparin differently, so it's normal to track heparin levels and change the dose based on blood test results. Heparin has to be given through a vein since it can't be taken orally.

The main ways it is administered are through shots under the skin or a steady IV drip. Since giving heparin under the skin reduces bioavailability, this dose must be higher than that administered lthrough IV.⁵

Warfarin

For a long time, the drug warfarin has been key in treating children with blood clot issues. For over 60 years, the only blood thinners given were vitamin K blockers, like warfarin.

By preventing the conversion of vitamin K epoxide to its active form through the vitamin K epoxide reductase complex (VKOR), vitamin K antagonists (VKAs) hinder the synthesis of vitamin K-dependent coagulation factors (II, VII, IX, and X). Warfarin and other VKAs are therefore used as anticoagulants to treat or prevent thromboembolism and in relation to thrombophilia, atrial fibrillation (AF), and prosthetic heart valves.⁶ Racemic mixes of warfarin are currently marketed as oral and parenteral medications; S-warfarin has an anticoagulant potency that is roughly five times greater than R-warfarin.

Long-term anticoagulant medication with warfarin is a conventional treatment for various illnesses observed in hospice and palliative care programs.⁹

Anticoagulating property

Long-term warfarin use has been found to lower the risk of stroke and systemic embolisation (SSE) in AF.¹ It provides preventative therapy for children with prosthetic heart valves and prevents thromboembolic consequences. Warfarin can stop clots in children with deep-vein clots or clots in main blood vessels. Many factors influence the dosage of warfarin needed, such as the child’s food intake, smoking habits, drinking habits, other medications, and genetic factors.

Dosage

Many factors can influence warfarin dosage, such as what the person eats, if they smoke, drink alcohol, other drugs they take, and their genes.

It is usual practice to begin warfarin with a fixed dose and gradually adjust the individual dose based on INR monitoring. Common parameters influencing warfarin dose in algorithms include age, race, body surface area, smoking, amiodarone, and statin usage.⁶ Good warfarin management is crucial due to the increased risk of complications. Children with prosthetic mitral valves may require a more intensive anticoagulant regimen due to placement and blood flow issues.

Adverse effects

Haemorrhage is the main risk associated with warfarin treatment. The first signs that there is too much warfarin can be bleeding gums when you brush your teeth, small red spots on skin, and blood in urine. Another severe dermatological reaction brought on by warfarin is the purple toes syndrome.

DOAC ( direct oral anticoagulants)

The top choice for many health issues has moved from vitamin K blockers to direct oral anticoagulants (DOACs), marking a big step forward in blood thinning treatment.¹¹ The first DOAC to get a green light for use in people was ximelagatran, known as a reversible thrombin stopper. The four DOACs that are now approved are edoxaban, apixaban, rivaroxaban, and dabigatran.

Anticoagulating properties

DOACs are now the top choice for VTE care in the latest health rules. Plain heparin is often used to help VTE patients who need clot-busting care for a big lung block or deep vein clots. Once they improve, they can move to a DOAC. DOACs act quicker than VKAs and don't last long in the body. This helps manage care during other health procedures and cuts down on the need for drugs that undo their impact.¹¹ DOACs lead to less brain bleeding compared to VKAs.

They help treat VTE, which covers clots in the lungs and deep veins.

They also help stop strokes in AF patients and prevent clots after surgery in patients getting hip or knee replacements. For postoperative thromboprophylaxis in orthopaedic patients, DOACs present an alluring substitute for LMWH.¹⁰ DOACs lower the danger of severe bleeding and remove the need for frequent coagulation monitoring and dose adjustments and they are reasonably priced.

Adverse effects

The rapid onset and offset effect of DOACs makes them simpler to start and handle during procedures. They can be handed out in fixed doses without the need for ongoing lab tests, making them easier to use than VKAs.Since they go through the placenta, they should not be taken during pregnancy, and mothers who nurse should avoid them.

General principles of anticoagulation

Medical anticoagulation consists of 3 phases

•  Acute (the first 5–21 days)
• Long-term (3–6 months)
•  Extended period

In the long run, the usual time to take blood thinners after surgery for VTE is 3 months due to a low chance it will come back. But, if the VTE has no clear cause, it stretches to 6 months.¹³At the start, strong blood thinners are given by shot or a high dose orally. In some cases with high risk of blood clots coming back, long-term care may be needed. For treating blood clots, heparin and VKA were often used for years. But now, DOACs are taking over since they are easier to use.

Treatment of various thrombosis

• In case of proximal deep vein thrombosis, 3 months anticoagulant therapy is indicated which includes warfarin, LMWH or DOAC
• While treating hemodynamically unstable pulmonary embolism, DOAC’s are the drug of choice. The duration of treatment varies around 3-6 months
• In case of cancer associated venous thromboembolism LMWH was used as a gold standard, but not DOAC’s act as alternatives
• In case of Cerebral venous thrombosis firstly unfractionated heparin (UFH) or low molecular weight heparin is given, typically followed by long-term vitamin K antagonists (VKA) for 3–12 months to prevent recurrence⁷
• Traditional anticoagulants commonly used for Splanchnic vein thrombosis are heparins and vitamin-K antagonists (VKA). Low-weight heparin (LMWH) is often chosen over normal heparin (UFH) because it leads to fewer cases of heparin-induced thrombocytopenia¹⁰
• In venous thromboembolism associated with pregnancy, LMWH is the treatment of choice
• In children with venous thromboembolism, options for acute anticoagulation include LMWH or UFH, for a time period of 6 weeks to 3 months

Summary

Over time, many ways to change heparin, such as chemical, chemoenzymatic, and metabolic methods, have been made. These methods work with different levels of success. They can change these structures or use them together to get the needed shapes of heparin for certain uses. Warfarin is often used to treat children with artificial heart valves and to stop blood clots that come with sickness. The development of DOACs are a big step forward in terms of blood thinner medications as they work just as well and are safer and easier to use than VKAs.