There are many arguments against nanomedicine due to the issue of toxicity. Elements at a microscopic level have different properties than they have at their standard conditions and every nano particle is completely unique so they each have different properties. These leads to the possibility of the nanoparticles having a serious effect on our health. Also if nano robots were used then serious issues can arise if there was a glitch in the programming and the nanoparticles had negative effects on us. These scenarios can only be resolved through thorough testing.
Financial costs are another disadvantage to nanomedicine. At first, the treatment will be too expensive to the average person so this leads to the thought that should we reform the health system before we start investing millions of pounds in nanomedicine rather than in gaining better access to medicine in LEDCs.
Furthermore, nanomedicine can be used for other purposes rather than helping people which is the main aim of the work in this field. Such technology can be used by the military for surveillance on people. Also if anyone one could have to this technology, then they could use it to enhance themselves which could raise more ethical questions.
The points above show that there are many questions that need to be answered before this technology is put to use.