If the dose is split 0.2mls twice a day, and if she is used to taking oral Vetergesic, and if this is palliative eldery care, it is fine. My arthritic old girl Clover has been taking 0.1mls Vetergesic orally for a while, up to twice a day as needed, along with 0.4mls cat metacam twice a day, and on Wednesday she had 0.2mls Vetergesic all at once as she was in serious leg pain and she wasnt sleepy or dazed at all, she had a quick nap then got up and started eating hay mych happier than she's been for a while!
Tolerance develops quite fast, but some animals tolerate buprenorphine better than others. If they have previously been ok taking 0.05 mls or 0.1mls, a slow increase should be fine- either short term for acute pain relief, or in the case of elderly piggies with palliative care aches and pains, as long as needed to keep them still with you but pain free x