We shall discuss homeopathic medicines in terms of the following points :

(a) Source
(b) Method of preparation
(c) Therapeutic application
(d) 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. The whole plant or some parts of it, such as leaves, roots, flowers, seeds, and berries, may be used in the preparation of the medicines. All types of plant, benign, poisonous, and carnivorous, have been used as homeopathic medicines.
   
   Common plant-based homeopathic medicines are Pulsatilla nigra, Bryonia alba, Aconite napellus, Belladona, Gelsemium, Coffea cruda, Rhus toxicodendron, etc.



2. Mineral kingdom : Approximately 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). The therapeutic properties of almost all known metals and non-metals and many important compounds have been exploited in homeopathy.



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



4. Diseased tissues : Some homeopathic medicines are prepared using tissues or secretions containing bacteria, viruses, and other microorganisms. Thus, homeopathy advocated the therapeutic use of 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 : Healthy human/animal tissues and secretions are also used to prepare homeopathic medicines. Examples of such medicines are Thyroidinum and Adreanline.



6. Imponderables: Certain energy sources, such as magnetism, x-ray, radiation, etc., are also used to prepare homeopathic medicines.

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 plant extract) is mixed with 99 parts (9.9 mg) of a suitable carrier (say alcohol) and shaken vigorously by a special device that converts the preparation into the 1c potency. 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. Homeopathic medicines are available in certain standard potencies such as 30c, 100c, 200c, 1000c, 10K, and 50K.

c. Application of homeopathic medicines :

The therapeutic 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. The clinical use of these medicines is governed by specific tried-and-tested laws and principles.

d. Adverse effects of homeopathic medicines :

Since only miniscule amounts of the original drug substance are used, homeopathic medicines, essentially, do not cause any adverse effects.