Simple and compound drugs (al-adwiya al-mufrada wal-murakkaba)

In the preface to Book II of the Canon, Ibn Sina says it is the second of the books he composed on medicine, the first dealing with general rules; this one is on simple drugs. He divides it in two parts: the first on the natural rules that must be known about drugs, the second on the powers of particular drugs ⁴. The first part has six treatises: on the temperaments of simple drugs, knowing them by experiment, knowing them by analogy, knowing the actions of their powers, rulings that arise from outside, and the collection and storage of drugs ⁴. The second part is made of tablets that arrange drugs by actions and properties, then by organ and disease, including a tablet for wounds and ulcers and one for poisons ⁴. This record describes what Ibn Sina wrote; it is not a description of any medicine and gives no treatment advice.

Ibn Sina reminds the reader that to call a drug hot, cold, moist or dry is said in relation to our bodies, and that the constituents of every compound, mineral, plant or animal, are the four elements. He distinguishes a first temperament, arising from the elements, from a second, arising from things that already have a temperament of their own, such as compound drugs and theriac; the second may be a strong, bound one or a loose one that parts easily ⁵. When physicians say a drug's power is compounded of opposing powers, he says, they do not mean one part holds heat and cold at once, but that its different parts hold different powers. His examples: chamomile holds a resolving and an astringent power that cooking does not separate; garlic has a cleansing, burning power and a heavy moisture that cooking does separate; and coriander cools when eaten but may dissolve when applied as a poultice ⁶.

Powers of drugs are known by two roads, analogy and experiment, he says, and he puts experiment first and gives it seven conditions. First, the drug must be free of an acquired quality: water, though cold by nature, heats while it is hot. Second, the illness tested on must be a single one: if agaric (al-gharīqūn) helps a phlegmatic fever, that does not show it is cold, because it may have helped by dissolving the phlegmatic matter. Third, the drug is tried on opposites. Fourth, the drug's power must be matched to the strength of the illness, so it is tried first on the weaker and increased gradually ⁷. Fifth, the time at which the effect appears is observed; sixth, whether the action continues always or for the most part; seventh, the trial must be on the human body, since a drug may be hot to a man and cold to a lion or a horse, as he supposes of rhubarb, and bish (aconite) has the property of poison for a man that it lacks for starlings ⁸. The museum has a record for these conditions: Ibn Sina's seven conditions.

As for analogy, he says its rules are taken from how quickly a drug turns to fire and heats, or how slowly; from how quickly it congeals; from smells and tastes; sometimes from colours; and from actions and powers already known, which give clear indications of unknown ones ⁸. He requires the things compared to be equal in consistency; if they differ in rarity and density the matter cannot be settled by speed alone, and he gives wine, which is hotter than gourd oil yet congeals faster ⁹.

Book V is the pharmacopoeia (al-aqrabadhin). It opens with a treatise on the need for compound drugs and has two parts: the standard compounds in the pharmacopoeias, and compound drugs tried against diseases ¹⁰. His reasons for compounding are several: no single drug may match a composite illness; one drug's power may need strengthening by another; a harm may need breaking by its counterpart; a bad taste may need sweetening; or a drug may need an escort so that it reaches the intended organ, as opium is put into theriac preparations ¹¹. He holds that the tried is better than the untried and that few drugs are better than many for a single aim ¹². In a compound some drugs are a pillar and foundation, like viper flesh in theriac, and removing them voids the formula; others may be dropped or replaced; and others would do harm if added ¹³. The continuation is in Theriac and poisons.

See also Treatment in the Canon and Medicine.