You will be shown a paragraph from a biomedical research article. Your task is to extract all drug combinations appearing in a specific sentence within in the paragraph. Each drug combination should be assigned to one of the following three categories:

- POS: Indicates a positive interaction between the drugs in the combination; for instance, drugs that have an additive or synergistic effect.
- NEG: Indicates a negative interaction between the drugs in the combination; for instance, combining these drugs might result in adverse side effects, or might reduce their efficacy.
- COMB: Indicates that the drugs are given in combination, but the type of interaction between the drugs cannot be determined based on the provided context.

Please format your answer as a json array. Each entry in the array should itself be an array formatted as [<drug_1>, <drug_2>, ..., <drug_n>, <category>] where <category> is one of the three categories listed above and <drug_1>, ..., <drug_n> are drug names copied verbatim from the input sentence. Different combinations may involve different numbers of drugs; in other words, the `n` in <drug_n> may vary.

As an example, the following output describes two extracted drug combinations; one between two drugs, and one between three drugs:

[["artesunate", "artemether", "COMB"], ["Nifedipine", "Labetalol", "Prazosin", "POS"]]

The paragraph and specific sentence are below. You should only extract relationships expressed in the specific sentence; the paragraph is provided for context.

In your output, return only the json array and no other text. If no drug combinations appear, return an empty array `[]`.

paragraph: [Reduction in the use of donated blood in surgical medicine]. After rapid changes in transfusion practice over the past few years, blood conservation techniques have become standard in modern perioperative management. As a result, the amount of homologous blood products transfused has been markedly reduced in some types of surgical procedures. Provided that skillful surgical technique is applied and the use of blood products is restricted, autologous transfusion techniques (predonation of autologous blood, preoperative plasmapheresis, acute normovolaemic haemodilution, and intra- and postoperative blood salvage) can be performed with an acceptable risk for patients. In addition , stimulation of erythropoiesis with recombinant human erythropoietin , supplemental iron therapy , and improving haemostasis by aprotinin may further reduce homologous blood requirements . All patients undergoing elective surgery have to be informed about the side effects of transfusion of homologous blood products and the possibility of blood-saving methods. An individual blood conservation plan, based on the patient's status and surgery, the equipment available, and personal experience should be worked out by the responsible anaesthesiologist, whereby a combination of different methods may be most effective. If storage is necessary, autologous blood products should be preparated like homologous products. The feasibility of predonation and retransfusion of autologous blood in patients with infectious diseases like hepatitis or acquired immune deficiency syndrome and the amount of labaratomy testing are still under discussion. Although blood conservation programs are time-consuming and more expensive, they reduce the various risks of using homologous blood products.

sentence: In addition , stimulation of erythropoiesis with recombinant human erythropoietin , supplemental iron therapy , and improving haemostasis by aprotinin may further reduce homologous blood requirements .
[["erythropoietin", "iron", "aprotinin", "POS"]]