The conceptual structure of opioids, based on the bibliometric analysis of 4,935 articles of the Web of Science using the following indices: Science Citation Index Expanded (SCI-EXPANDED), Social Sciences Citation Index (SSCI), Conference Proceedings Citation Index-Science (CPCI-S), Conference Proceedings Citation Index- Social Science and Humanities (CPCI-SSH), Book Citation Index-Science (BKCI-S), Book Citation Index-Social Sciences and Humanities (BKCI-SSH) and Emerging Sources Citation Index (ESCI), was constructed. We analyzed the available articles with the words "Opioids" and "Cancer." We show the evolution and the state of the art in countries where these treatments are implemented. The results were processed identifying the most cited articles to extract the main connections and frequencies of keywords, authors, journals, countries, institutions, and their tendencies and their connection and degree of collaboration. The temporal tendencies, the word cloud, the keyword network, the evolution of words, author's production, and the scientific production by country are analyzed in terms of the increasing frequency in which opioids are employed to treat both cancerous and non-cancerous pain.