The time to buy them might be after they cut their dividend.
The (almost certain) dividend cut may be announced in conjunction with 4Q17 results in early February. If not then, it will happen sooner, IMO. (The 4Q17 CC will be the first call led by the new CEO, who made a token appearance to say hello on the 3Q17 CC.)
Meanwhile, 2017 guidance for operating cash flow is a scant $3.15-3.3B.
TEVA has not yet issued any guidance for 2018, but it’s hard to see how 2018 EBITDA could exceed $5B, particularly with the likelihood of a second generic 40mg Copaxone in the US market (from NVS/MNTA). So, in the best-case scenario, net debt at the end of 2017 will be at least 6x 2018 EBITDA.