thumb|Coverpage of facsimile edition of 1899 Merck's Manual of the Materia Medica
The Merck Manual of Diagnosis and Therapy, referred to as The Merck Manual,
is the world's best-selling medical textbook, and the oldest continuously published English language medical textbook. First published in 1899, the current print edition of the book, the 20th Edition, was published in 2018. In 2014, Merck decided to move The Merck Manual to digital-only, online publication, available in both professional and consumer versions; this decision was reversed in 2017, with the publication of the 20th edition the following year. The Merck Manual of Diagnosis and Therapy is one of several medical textbooks, collectively known as The Merck Manuals, which are published by Merck Publishing, a subsidiary of the pharmaceutical company Merck Co., Inc. in the United States and Canada, and MSD (as The MSD Manuals) in other countries in the world. Merck also formerly published The Merck Index, An Encyclopedia of Chemicals, Drugs, and Biologicals.
History and editions
The first edition of The Merck Manual was published in 1899 by Merck & Co., Inc. for physicians and pharmacists and was titled Merck's Manual of the Materia Medica. The 192 page book which sold for US $1.00, was divided into three sections, Part I ("Materia Medica") was an alphabetical listing of all known compounds thought to be of therapeutic value with uses and doses; Part II ("Therapeutic Indications") was an alphabetical compendium of symptoms, signs, and diseases with a list of all known treatments; and Part III ("Classification of Medicaments (sic) According to their Physiologic Actions") was a listing of therapeutic agents according to their method of action or drug classification.
The earliest versions did contain drugs that are still in use today for the same purposes, for example digitalis for heart failure;,
The 5th edition, published in 1923 was delayed due to paper shortages caused by World War I, and the release of the 6th edition was delayed until 1934 due to the Stock Market Crash. The editor of that edition, Dr. M. R. Dinkelspiel had overseen the growth and reorganization of the Manual to discuss specific diseases, diagnosis and treatment options, and external specialists reviewed each section. The 8th edition of the Manual was delayed by World War II until 1950.
The 13th edition, released in 1977 was the first time the textbook was produced using magnetic tape and IBM punch cards, the previous version having been typed on a manual typewriter. The Centennial (17th) Edition published in 1999 included a separate facsimile version of the 1899 1st edition.<!-- It is likely that one of these sources is dependent on the other, or both on a third source. -->
The recommended doses given in Part 1 of 1901 edition of The Manual were for adults when given by mouth. It included the following dose adjustment recommendations: