B: Blood and blood forming organs

ATC group B covers the blood and the organs that make it: drugs that prevent clots or stop bleeding, anemia treatments, blood substitutes and IV fluids.
Updated

September 25, 2026

Drugs acting on blood itself and on the organs that make it.

In February 1933 a farmer, Ed Carlson, drove 190 miles with a dead heifer, a milk churn full of her unclotted blood and a pile of moldy straw. He was looking for the state veterinarian, and instead found Karl Paul Link’s laboratory at the University of Wisconsin in Madison. In June 1939 Harold Campbell, one of Link’s assistants, isolated the substance later named dicoumarol (B01AA01), a breakdown product of the coumarin in spoiled hay. Warfarin (B01AA03) was another of the group’s compounds, first marketed as a rodenticide [1]. It went on to become one of the most commonly prescribed drugs in history [2].

Table 1: ATC B level 2 codes
Description In plain terms Example drug
B01 Antithrombotic agents prevent or dissolve blood clots Apixaban (B01AF02) / clopidogrel (B01AC04)
B02 Antihemorrhagics stop or prevent bleeding Tranexamic acid (B02AA02) / phytomenadione (B02BA01)
B03 Antianemic preparations Ferrous sulfate (B03AA07) / cyanocobalamin (B03BA01); parenteral iron carries only the group code B03AC, with no level 5 substance
B05 Blood substitutes and perfusion solutions intravenous fluids, nutrition, dialysis and irrigation solutions No single INN to name: ATC codes solution classes, not substances. Crystalloid resuscitation fluid sits at electrolytes (B05BB01) and dextrose infusion at carbohydrates (B05BA03)
B06 Other hematological agents leftover blood drugs: attacks of deep swelling (angioedema), sickle cell Lanadelumab (B06AC05) / icatibant (B06AC02)

Measuring the effect

For the antithrombotic apixaban (B01AF02, see B01), the effect is measured as anti-factor Xa activity, a continuous laboratory value that rises linearly with plasma concentration [3]. For the drugs that stimulate red blood cell production (erythropoiesis-stimulating agents), such as darbepoetin alfa (B03XA02, see B03), it is hemoglobin, another continuous laboratory value, on which the dose is titrated [4]. For factor VIII replacement in hemophilia A (coagulation factor VIII, B02BD02), the population PK model of efanesoctocog alfa was fitted to factor VIII activity, and bleeding episodes were modeled as repeated time-to-event data, with a hazard that depended on factor VIII activity [5].

References

[1]
Ball CM, Featherstone PJ. The history of warfarin. Anaesthesia and Intensive Care 2025;53:148–50. https://doi.org/10.1177/0310057X251323777.
[2]
Wardrop D, Keeling D. The story of the discovery of heparin and warfarin. Br J Haematol 2008;141:757–63. https://doi.org/10.1111/j.1365-2141.2008.07119.x.
[3]
Byon W, Garonzik S, Boyd RA, Frost CE. Apixaban: A clinical pharmacokinetic and pharmacodynamic review. Clinical Pharmacokinetics 2019;58:1265–79. https://doi.org/10.1007/s40262-019-00775-z.
[4]
Mahar KM, Yang S, Johnson B, Visser SAG, Berg P van den, Noort M van, et al. Model-informed drug development for daprodustat supports the design of individualized dosing regimens in chronic kidney disease patients with anemia. Clinical Pharmacology & Therapeutics 2026;119:322–35. https://doi.org/10.1002/cpt.70094.
[5]
Wong N, Bhagunde P, Nyberg J, Katragadda S, Demissie M, Willemze A, et al. Efanesoctocog alfa population pharmacokinetics and repeated time-to-event analysis of bleeds in adults, adolescents, and children with severe hemophilia a. The Journal of Clinical Pharmacology 2025;65:860–72. https://doi.org/10.1002/jcph.70008.