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: Continuous-infusion ifosfamide and doxorubicin combination as second-line chemotherapy for recurrent or refractory osteosarcoma patients in China: a retrospective study. The aim of this retrospective study was to evaluate the feasibility and efficacy of response to continuous-infusion ifosfamide and doxorubicin combination as second-line chemotherapy for patients with recurrent or refractory osteosarcoma. ### Materials And Methods Eighteen recurrent or refractory osteosarcoma patients who were treated with continuous-infusion ifosfamide and doxorubicin combination between May 1999 and April 2011 were included in the analysis. Ifosfamide at 12 g/m2 was administered by intravenous continuous infusion over 3 days , and doxorubicin 60 mg/m2 was administered as an intravenous bolus injection on day 1 . The combination therapy was repeated every 3 weeks. Treatment was continued until evidence of disease progression or unacceptable toxicity. ### results The patients (ages 7-53 years) received a total of 42 cycles of chemotherapy (median: 2 courses; range: 2-5 courses). The overall response rate was 0% and the disease control rate was 22.3%, with four patients having stable disease. The median time to progression and overall survival time were 2 months (range: 2-5 months) and 9 months (range: 3-29 months), respectively. Major severe toxicities were leucopenia 7 (38.9%), nausea and vomiting 3 (16.7%) and alopecia 9 (50%). There were no treatment-related deaths. ### conclusions In our experience, continuous-infusion ifosfamide and doxorubicin combination therapy at this dosage and schedule was found to be well tolerated and moderate effective, which could be considered as salvage therapy for patients with recurrent or refractory osteosarcoma. Further assessment is necessary to confirm the safety and efficacy of this treatment.

sentence: Ifosfamide at 12 g/m2 was administered by intravenous continuous infusion over 3 days , and doxorubicin 60 mg/m2 was administered as an intravenous bolus injection on day 1 .
[["Ifosfamide", "doxorubicin", "POS"]]