From what I've read about pharmaceutical lobbying, it consists primarily of things like buying doctors free meals for in exchange for using the company's drug instead of a competitor's drug.

No. It also consists of lobbying the relevant politicians to make it hard to sue doctors and generally policies to reduce harms caused by drugs. Drugmakers fought state opioid limits amid crisis:

The makers of prescription painkillers have adopted a 50-state strategy that includes hundreds of lobbyists and millions in campaign contributions to help kill or weaken measures aimed at stemming the tide of prescription opioids, the drugs at the heart of a crisis that has cost 165,000 Americans their lives and pushed countless more to crippling addiction.

The drugmakers vow they're combating the addiction epidemic, but The Associated Press and the Center for Public Integrity found that they often employ a statehouse playbook of delay and defend that includes funding advocacy groups that use the veneer of independence to fight limits on the drugs, such as OxyContin, Vicodin and fentanyl, the narcotic linked to Prince's death.

If so, this shows it's not a very risky drug--it rarely causes side effects that are nasty enough for a patient to want to sue their doctor.

That argument assumes that only side effects that can be proven in court to be bad are meaningful to worry about. Giving that establishing causation of drug effects usually takes millions of money to run well controlled studies that get published in leading medical journals that allow the drug companies that publish the studies that don't follow best standards of science that the journals pledged to honor (the CONSORT standards), it's not easy to prove all causation.