1. Idiosyncrasy

- Many persons are peculiarly susceptible to the action of certain medicines; no reason can be assigned for this extreme susceptibility, but of the fact of its existence in some individuals there can be entertained no reasonable doubt. A few grains of a mercurial salt, only sufficient to act, in ordinary cases, as a very slight stimulant of the biliary secretion, will, when an idiosyncrasy exists with respect to this medicine, produce the most violent salivation, and other untoward effects. Under such circumstances, three five-grain doses of blue pill, one being administered every night, have proved fatal: two grains of Calomel have caused ulceration, exfoliation of the jaw, and death; and the external application of three drachms of mercurial ointment has destroyed life in eight days. (Christison.) Other medicines act in a similar manner on certain constitutions. Opium, even in the smallest dose, will produce furious delirium and extreme disturbance of the cerebral and nervous functions; the very smell of Ipecacuanha will, in some constitutions, cause the most distressing sense of suffocation; Copaiba, inflammation of the kidneys; and Squills and Oil of Turpentine, eruptions on the skin. It should always be ascertained, if possible, previous to the exhibition of these remedies, particularly in the cases of Mercury and Opium, if any idiosyncrasy with respect to them exists; and if so, the obnoxious medicine should in every form be carefully avoided.

2. Sex

- Women, from their more delicate organization and greater nervous susceptibility, seldom bear the same doses as men. Those which will produce only a mild and beneficial effect upon the adult male, will, in the majority of cases, produce a prejudicially violent one upon an adult female. There are, of course, many exceptions to this, but as a general rule it holds good. Great care is necessary in the administration of irritating purgatives, particularly of Aloes, during the periods of pregnancy and menstruation; of Sulphuric Acid during lactation, as it renders the milk disagreeable and griping to the infant; and of Mercury in Anaemic Chlorosis.

3. Age

- In old age and in childhood, the same doses are not generally so well borne as in youth and manhood; and much nicety is sometimes necessary in regulating the dose. Several exceptions, however, present themselves; thus, in childhood and in old age, much larger quantities of Mercury are necessary to induce salivation than in manhood; indeed, Dr. Clarke states that, in a practice of twenty years, he never saw a child truly salivated: an observation corroborated by the experience of others. Prof. Graves ascribes the difficulty of inducing salivation in children and in old persons to the undeveloped state of the salivary glands in the former, and to their atrophied state in the latter. On the other hand, in infancy and childhood. Opium in every form is a remedy that requires the utmost caution in its administration. Two and a half drops of Laudanum have destroyed an infant three days old; three drops a strong child of fourteen months; and four drops a child of a few weeks old. (Christison.) Excepting under urgent circumstances, an opiate should never be administered to an infant; and when imperatively called for, its effects should be carefully watched. In infancy and childhood, blisters allowed to remain long in contact with the skin are apt to induce ulceration and gangrene; and leeches, on account of the thinness of the skin, and the vascularity of the subjacent tissues, draw more blood, and consequently make a more decided impression on the system in an infant, than a proportionate number would produce in an adult.

The following complete scale of doses, in use at Guy's Hospital, is quoted by Dr. Pereira: -

Age.

Maximum Dose.

The Apothecaries' Ounce, 480 grains ( j).

The Apothecaries' Drachm, 60 grains. (3j).

The Apothecaries' Scruple, 20 grains. j).

Months.

1 .

3ss. (gr. xxx.)

gr. iij.

gr. j.

3 .

-

iv.

-

6 .

ij. (gr. xl.)

,, vj.

,, ij-

9 .

-

vij.

-

Years.

1 .

3j- (gr- lx )

viij.

iij.

2 .

3iss. (gr. xc.)

x.

iv.

3 .

3iss. (gr. xc.)

xii.

4 .

3ij. (gr. cxx.)

xv.

v.

5 .

3iiss. (gr. cl.)

xviii.

vj.

6 .

3iij. (gr. clxxx.)

j. (gr. xx.)

vij.

7 .

3iiiss. (gr. ccx )

gr. xxv.

viij.

8 .

ss. (gr. ccxl.)

3ss. (gr.xxx.)

x.

10 .

3ivss. (gr. cclxx.)

gr. xxxv.

xij.

12 .

3v. (gr. ccc.)

ij. (gr. xl.)

xiv.

13 .

3vss. (gr. cccxxx.)

xv.

15 .

3vj. (gr. ccclx.)

gr. xlv.

xvj.

18 .

3viss. (gr. cccxc.)

-

xvij.

20 .

3vij. (gr. ccccxx.)

gr.1.

xviij.

21 to 45 .

j. (gr. cccclxxx)

3j- (gr- lx)

j. (gr. xx.)

50 .

3vij. (gr. ccccxx.)

gr. 1.

gr. xviij.

60 to 70 .

3vj. (gr- ccclx.)

gr. xlv.

xvj.

80 to 90 .

3v. (gr. ccc.)

ij. (gr. xl.)

xiv.

100 .

ss. (gr. ccxl.)

3ss. (gr. xxx.)

x.