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: Platelet aggregation and coagulation inhibitors in leech saliva and their roles in leech therapy. Prolonged bleeding by the host after the leech ceases to feed and several reports that the use of leeches restores blood flow in the microcirculation after plastic surgery led us to search for inhibitors of platelet aggregation in Hirudo medicinalis saliva. Dilute leech saliva was collected by phagostimulating starved leeches with a solution of arginine in saline. The saliva is shown to inhibit human platelet aggregation induced by thrombin , collagen , adenosine diphosphate ( ADP ) , epinephrine , platelet activating factor ( 1-O-alkyl-2-acetyl-sn-3-glycerophophoryl choline [ PAF ] ) , and arachidonic acid . We have isolated the PAF inhibitor and found it to be an amphipathic phosphoglyceride. We have also purified apyrase adenosine triphosphate ([ATP] diphosphohydrolase), which inhibits ADP-induced platelet aggregation, and have described collagenase. Besides well-known hirudin, Hirudo saliva contains a potent inhibitor of coagulation factor Xa. We also report antiaggregant and anticoagulant activities in the crop content of the closely related Nile leech, Limnatis nilotica. Anticoagulants of hematophagous species are surveyed. We have used medicinal leeches in plastic surgery for decompression of skin flaps and in patients with postphlebitic syndrome and peripheral arterial occlusions. Preliminary results indicate certain beneficial effects of leech therapy.

sentence: The saliva is shown to inhibit human platelet aggregation induced by thrombin , collagen , adenosine diphosphate ( ADP ) , epinephrine , platelet activating factor ( 1-O-alkyl-2-acetyl-sn-3-glycerophophoryl choline [ PAF ] ) , and arachidonic acid .
[]