Despite the surge in the research of cannabis chemistry and its biological and medical activity, only a few cannabis-based pharmaceutical-grade drugs have been developed and marketed to date. Not many of these drugs are Food and Drug Administration (FDA)-approved and some are still going through regulation processes. Active compounds including cannabinergic compounds (i.e., molecules targeted to modulate the endocannabinoid system) or analogs of phytocannabinoids (cannabinoids produced by the plant) may be developed into single-molecule drugs. However, since in many cases treatment with whole plant extract is preferred over treatment with a single purified molecule, some more recently developed cannabis-derived drugs contain several molecules. Different combinations of active plant ingredients (API) from cannabis with proven synergy may be identified and developed as drugs to treat different medical conditions. However, possible negative effects between cannabis compounds should also be considered, as well as the effect of the cannabis treatment on the endocannabinoid system. FDA registration of single, few or multiple molecules as drugs is a challenging process and certain considerations that should be reviewed in this process, including issues of drug-drug interactions, are also discussed here.