Posology means a study of doctrine of doses of medicine. Homoeopathic dose include potency quantity form and number of administration of medicine. Author Stuart close in his book “Genius of homoeopathic lectures and essay on Homoeopathic philosophy” stated that ‘series of potency has been comparing to the gamut in music a skillful artist may indeed construct a harmony with the various vibrations of the same called but what a more beautiful and perfect harmony might be constructed by a proper combination of all the sounds that can be elicited from his instrument.’ 

Following five points should be considered in the choice of dose:

• Susceptibility of the patient       

• Seat of the disease

• Nature and intensity of the disease 

• Stage and duration of disease 

• Previous treatment of the disease 

Selection of potency in spite of the correctly selected medicine on the basis of totality of symptoms it will not act curetively unless it is given in proper potency.

 Division of Potency

• Low potencies below 30
• Medium potencies between 30 to 1 m 
• High potencies above 1 m

Various Kinds of Doses

• Maximum Dose: It is the maximum or largest possible amount of medicine, which can be taken at a time by an adult, not harmful to human life

• Lethal or Fatal Dose: It is also known as toxicological or narcotic dose. It is such amount of dose, which can cause death of living being. The fatal dose of different substances may be different, which depend upon their toxicity

• Booster Dose:  A subsequent dose given to enhance the action of initial dose

• Fractional or Refractive or Divided Dose: It is fraction of a full dose, which is to be taken at short intervals

• Physiological Dose: Physiological doses are those which stimulates the normal physiology or functions of the different organs or systems of our body 

• Minimum Dose: It is that dose which is sufficient to overpower and annihilate the disease and capable of producing slight homoeopathic aggravation scarcely observable after its ingestion. It is that amount of medicine, which is though smallest in quantity produces the least possible excitation of the vital force, and yet sufficient to effect the necessary changes in it

There are no hard and fast rule for selection of potencies, susceptibility is the only guides for the selection   of   courts   to find out the susceptibility of patient the physician must be qualified through the knowledge of allied subject; "More the susceptibility, higher the potency – less the susceptibility, lower the potency."  Various factors contribute to assume the susceptibility of the patient, they are age, sex, habit and environment, constitution and temperament, nature of disease, structural changes, suppression, mental and physical reaction to environmental stimuli.

Voisin has clearly stated that low potencies are organotrophic medium potencies influence functions and higher potencies are for the psychology. Homoeopathic posology represents the accumulated clinical experiences and interpretation of all careful prescribers since the times of Hahnemann.  A proper understanding of the dynamic concept of disease of susceptibility and of remedy reaction is essential for an intelligent grasp of this most important aspect of homoeopathic practice. Hahnemann was all the time modifying and changing his ideas of posology in the light of its clinical experience.

1. Close, R.L. The Genius of Homoeopathy: Lectures and Essays on Homoeopathic Philosophy with Word Index. 2nd ed., 2005, ch. 13, pp. 237–239.

2. Mandal et al. Textbook of Homoeopathic Pharmacy. 2015, ch. 29, pp. 397–400.

3. Banerjee, N.K., et al. N-Treatise on Homoeopathic Pharmacy. B. Jain Publishers (P) Ltd., 2001, pp. 78, 309, 449.

4. Mandal et al. Textbook of Homoeopathic Pharmacy. B. Jain Publishers (P) Ltd., 2011, p. 384.

5. Goel, Sumit. Art and Science of Homoeopathic Pharmacy. 1st ed., 2002.

6. Kakkar, Dhiraj. External Application in Clinical Practice. Narayana Verlag GmbH, Blumenplatz 2, D-79400 Kandern, Germany.

7. Sahani, M.K. Principles and Practice of Homoeopathic Pharmacy for Students. 1st ed., B. Jain Publishers (P) Ltd., 2007, pp. 6–8.

8. Banerjee, D.D. Augmented Textbook of Homoeopathic Pharmacy. 2nd ed., B. Jain Publishers (P) Ltd., 2006, pp. 55, 78, 309, 449.

9. Hahnemann, Samuel. Organon of Medicine. 1833, paras. 186, 193–203. B. Jain Publishers.

10. Roberts, H.A. The Principles and Art of Cure by Homoeopathy. B. Jain Publishers, 2002, ch. 1, p. 15.

11. Sahani, M.K. Principles and Practice of Homoeopathic Pharmacy for Students. 1st ed., B. Jain Publishers (P) Ltd., 2007, pp. 6–8.

12. Hahnemann, Samuel. Organon of Medicine. 6th ed., Indian Books & Periodicals Publishers, 2010, aph. 194, pp. 221–222.

13. Boericke, William. Dr. Samuel Hahnemann; Organon of Medicine. 6th ed., Hahnemann’s Own Written Revision, B. Jain Publishers Pvt. Ltd., 2004. ISBN: 81-7021-085-2.

14. Das, Ashok Kumar. A Treatise on Organon of Medicine. Part-I, 5th ed., Books and Allied (P) Ltd., 2002. Souvik Homoeo Publications, Calcutta.

15. Sarkar, B.K. Organon of Medicine. Reprint ed., Bhattacharya and Co., Calcutta, 1987, p. 289.