Short answers, pulled from the story.
The word analgesic derives from the Greek an meaning without and algos meaning pain. Before the 20th century these drugs were known as anodynes which suggests a gentle soothing rather than the complex neurochemical intervention we understand today.
Paracetamol inhibits prostaglandin synthesis in the central nervous system and its effects last between two and four hours. It is typically used for mild to moderate pain and fever and is generally safe at recommended doses.
Research suggested most of the adverse effects of NSAIDs to be mediated by blocking the COX1 enzyme which is constitutive. The analgesic effects are mediated by the COX2 enzyme which is inducible and this discovery led to the development of COX-2 inhibitors.
Dosing of all opioids may be limited by opioid toxicity which includes confusion respiratory depression myoclonic jerks and pinpoint pupils. Patients starting morphine may experience nausea and vomiting while constipation occurs in almost all patients on opioids.
Drugs like gabapentin and pregabalin are prescribed for neuropathic pain and phenibut is available without prescription. Ziconotide is administered intrathecally for the relief of severe usually cancer-related pain and adjuvant analgesics include orphenadrine mexiletine cyclobenzaprine and hyoscine.
After widespread adoption of the COX-2 inhibitors it was discovered that most of the drugs in this class increase the risk of cardiovascular events by 40% on average. This led to the withdrawal of rofecoxib and valdecoxib and warnings on others.