Homeopathic medicines can be examined under the following headings :

1. Source
2. Method of preparation
3. Therapeutic application
4. Adverse effects

a. Source

Homeopathic medicines are prepared from the following 6 major sources :

1. Plant kingdom : About 60% of the homeopathic medicines are prepared from one or more parts of plants, such as leaves, roots, flowers, seeds, berries, and whole plants. All types of plants, benign, poisonous, and carnivorous, are used, in full or in part, in the preparation of homeopathic medicines.
   
   Common plant-based homeopathic medicines are Pulsatilla nigra, Bryonia alba, Aconite napellus, Belladona, Gelsemium, Coffea cruda, Rhus toxicodendron, etc.


2. Mineral kingdom : About 20% of the homeopathic medicines are prepared from minerals, including metals, non-metals, and their compounds. Some of the medicines prepared using minerals are Aurum metallicum (gold), Kali carbonicum (potassium), Natrum muriaticum (common salt), and Silica (sand). Almost all known metals and many important compounds have been used in homeopathy for their therapeutic properties.


3. Animal kingdom : Certain animal products, which are obtained without killing animals, are also used as homeopathic medicines. These include snake poison, spider poison, etc., which are used in extremely minute doses to prepare homeopathic medicines.
   
   Examples include : Tarantula hispania, Lachesis, Ambra gresia, Bufo rana, and Naja naja, etc.


4. Diseased tissues : Some homeopathic medicines are prepared using tissues or secretions containing bacteria, viruses, and other microorganisms. Thus, homeopathy used miniscule amounts of microorganisms long before the introduction of vaccines. Some commonly used homeopathic medicines prepared in this manner include Tuberculinum, Syphillinum, and Variolinum.


5. Hormones and healthy tissues : Certain homeopathic medicines are derived from healthy human discharges as well as tissues. Examples of medicines prepared in this manner include Thyroidinum and Adreanline.


6. Imponderables : In homeopathy, certain invisible substances and energy sources, such as magnetism, x-ray, radiation, etc. are used to prepare certain homeopathic medicines by specific methods.

b. Method of preparation: Potentization :

Homeopathic medicines are essentially nano-medicines. The original drug substance is used in extremely minute quantities to prepare a given homeopathic medicine. The method of preparing homeopathic medicines is called potentization; in this method, one part of the original drug substance (say, 0.1 mg of a salt) is mixed with 99 parts (9.9 mg) of a suitable carrier (say lactose) and shaken vigorously by a special device that converts the preparation into 1c potency or power. One part (0.1 mg) of the 1c preparation is then mixed with 99 parts (9.9 mg) of the carrier and the process of potentization is repeated to prepare the 2c potency. This process is continued until the required potency is reached. Standard potencies of homeopathic medicines are 30c, 100c, 200c, 1000c, 10K, 50K, etc.

c. Application of homeopathic medicines :

The clinical application of homeopathic medicines is based on the Law of Similars. All homeopathic medicines are tested on humans, by a method that is similar to clinical trials, before use. Further, their application is governed by certain laws and principles.

d. Adverse effects of homeopathic medicines :

Due to the very nature of preparation of homeopathic medicines, they do not cause any adverse effects.