Homeopathic Medicines and Nanoparticles: A Critical Narrative Review

The biological mechanism behind the action of homeopathic medicines (HMs) is a matter of debate, despite the fact that many studies have been put forth to demonstrate its efficacy. The occurrence of nanoparticles (NPs) in homeopathic remedies has been the subject of recent studies. NPs in homeopathic triturations and dilutions have been characterized using various analytical methods, including spectroscopic and microscopic techniques.We made a comprehensive literature search of articles in which HMs were characterized using any of the relevant characterization techniques. A narrative review of the strengths and limitations of the studies retrieved was made.A total of 33 articles were retrieved and thoroughly reviewed, including aspects of study design and methods. Scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Raman spectroscopy, nanoparticle tracking analysis, nuclear magnetic resonance spectroscopy, inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectroscopy, dynamic light scattering, zeta potential, ultraviolet-visible spectroscopy, and Fourier transform infrared spectroscopy are techniques that have been employed to date to explore HMs for NPs. Though a few studies were of good methodological quality, many presented poor design in the form of lack of control groups, deployment of a single microscopic technique alone for characterization, and sometimes insufficient limit of detection of the instruments involved. Additional characterization of HMs may be approached using methods such as wavelength dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and neutron scattering.With more robust protocols and suitable combinations of existing characterization techniques, the precise characteristics of NPs in HMs and their role in the pharmacology of homeopathy can be more clearly understood.