The pharmacodynamics of khat




Author: Michel Trellu
Pages: 43 to 44
Creation Date: 1959/01/01

The pharmacodynamics of khat

Dr. Michel Trellu


The drug is seen commonly in the form of small bundles of the leafy twigs; these bundles are tied with thin strips of bark, and wrapped up in banana leaves to preserve their initial freshness - the most important quality for the purpose of chewing.

It is a euphoric medicament which, although not containing caffeine, has been compared with caffeic substances - kola, tea, mate, coffee and even coca.

This drug is a native of Arabia Felix; in Yemen three species are cultivated in three different provinces (Saber, Taris and Mogtaria), of which the first two produce a better quality of khat. It has spread enormously in Ethiopia, into which it was first imported in 1429, and where it is now cultivated, and consequently in French Somaliland, where it is merely consumed, and also further south in East Africa.

Historical Backround

The khat of the Arabs, which is also called tschat or dimina by the Gallas of Harar, appears to enjoy divine blessing and the Hararis honour it as a sacred plant. There was even a time when no private or religious ceremony took place without the ritual chewing of the leaf accompanied by much praying, and chanting. This (it was reported) induced a state of religious exaltation among the Moslems of Harar, which they regarded as a gift from heaven.

Unlike Moslems, Christian peoples do not use this drug, but merely cultivate it for trade purposes. It is interesting to note, incidentally, that at Harar it is the women who are in charge of the khat fidcls and that the husbands have nothing to do with this business.

In modern times, it seems that the ritual chewing of khat is longer important, but it should be noted that the indigenous inhabitants feel an urge to gather in groups of at least five or six persons in order to chew khat while reciting verses from the Koran.

Consumption is none the less considerable; it amounts to 750 kg daily, or 200 tons yearly.

Botanical Characteristics

" Catha Edulis Forrsk" belongs to the celastracae family, to which the spindle-tree also belongs, and is closely related to the rhamnaceae family, the principal member of which is the alder.

It is a shrub of the tea or mate type, thornless, with smooth twigs; its leaves are coriaceous, with short stalks; and it grows mostly on hillsides and mountain slopes in clumps or in beds, and is pruned in order to obtain many any young twigs with very tender leaves, which are the best for chewing. The leaves, which are almost tasteless, though slightly bitter and astringent, are 8 to 11 cm long and 2 to 5 cm wide, the median veins and the stalks being slightly reddish in colour.

Khat is propagated by cuttings; its cultivation demands a good deal of care, and - in particular - daily watering and a certain amount of manure. Picking may begin when the shrubs are three years old; only the young twigs are cut off, at the level of the first two small branches. After the picking, the shrubs, which are reduced to a few branches bearing buds, grow for another three years before they are again picked.

These twigs are sold directly to the trade; only the youngest leaves of the central twig, which are greenish-brown in colour, are used for consumption. The leavesof the two lateral twigs are thrown away as being unfit for consumption. (Perhaps they are too tough for chewing, or possibly they do not contain the active stimulating principle.)

Khat is used as a stimulant in two ways: either the fresh leaf is chewed or else the leaves are used in preparing local drinks - talla, a sort of beer; tedji, a sort of wine. A third method, is to use the dried leaves for making a refreshing but non-stimulating infusion; the indigenous inhabitants, who want to experience the sensation of euphoria, categoriclly refuse to take this infusion.

Composition of Khat

This drug consists of resinous and pectic substances, an essential oil, alkaloids, tannin, choline and mannite.

The aromatic essential oil which has a pleasant odour slightly reminiscent of that of coal tar, is a pale yellow liquid, warm to the taste. It turns brown when exposed to the air and leaves a deposit of pearly crystals of an agreeable odour,resembling that of methyl eugenol.

There are three alkaloids - two amorphous alkaloids (cathinine and cathidine); whose properties are so far unknown; one crystallized alkaloid (cathine C 10H 18N 20), to which khat owes its spectacular properties.

Cathine was identified by Wolfes in 1930 with d-nor-pseudo-iso-ephedrine which is a demethylated ephedrine and an oxidated orthedrine. Cathine is soluble in ether and chloroform, and its salts are soluble in water; addordingly, cathine should be classed as one of the usual alkaloids.


Cathine is extracted by means of chloroform, in the presence of diluted ammonia. The solution is then concentrated and shaken with hydrochloric water. It is precipitated again with ammonia, and a white precipitate is obtained which is recrystallized by precipitation in an alcohol and chloroform mixture.

Cathine, which is a very hygroscopic powder, is soluble in ordinary organic solvents, and turns violet upon the addition of sulphuric acid together with potassium bicarbonate (identical reaction to that of strychnine).

Orthedrine: sulphate of pseudo-1-amino-2propane

C 3H 5CH 2-CH-CH 3

NH 2



NH 2




Pharmaceutical Properties

Cathine is, as a matter of fact, only slightly toxic, at least for Europeans.

Tests have been carried out on various laboratory animals - in weak doses it induces only a slight excitation of voluntary movements, without - increasing reflex excitability up to the stage of mechanism, or producing muscular rigidity, which occurs in tests with caffeine.

If a sub-lethal dose is administered there is at first excitability - the animal jumps about, foams at the mouth and then calms down. Respiratory movements cease,muscles relax, and symptoms of limp paralysis appear; sensitivity is retained, motor action and reflex excitability disappear; the heart slows down and then stops in systole.

In guinea pigs and rabbits similar phenomena are more marked, and after an injection of 3-4 cg/kg death occurs in three or four hours, accompanied by convulsions and early muscular rigidity.

If non-lethal doses are administered, signs of excitation with slight motor incoordination and dilation of the pupils are noticed (this may seem paradoxical, since it appears that the pupils of a human being under the influence of khat do not dilate). Respiratory movements are accelerated and the temperature rises by 1 to3 degrees. Furthermore, a phenomenon pointing to the effect on temperature is observed on the quays of Djibouti: men under the influence of khat sometimes - even in midsummer and in the noon-day sun - feel the need to warm themselves by a wood fire; this is definite evidence of a rise in body temperature.

Cathine therefore particulary affects the nervous system.

To sum up: this drug has, firstly, the primary nervine properties of cocaine, resembling in small doses those of morphine (without, however, possessing the latter's local anaesthetic and analgesic properties) and, secondly, toni- cardiac and tonimuscular properties closely related to those of cocaine.

Its psychological effect on man is that of an euphoria-producing stimulant; it facilitates the metabolism without increasing diuresis. Khat acts through the oxidation of fatty substances and tissues, and momentarily, accelerates the blood circulation. It thus stimulates man to work, suppresses the desire for sleep and the sensation of fatigue in workers. In the first stage ideas are clear and the brain works fast - the individual finds it easy to carry out his plans, is fresh, willing and hard-working (khat quickens the reactions).

Its abuse causes intoxication, a dazed condition (which is often noticed among Somali "boys") and cardiac disorders. The intellectual faculties of the indigenous inhabitant are seriously impaired by khat.

The effect of khat from the sexual point of view seems to be to dull desire. Khat acts like coffee, which according to Trousseau is one of the most potent anaphrodisiacs. Its habit-forming properties - as may be observed in the individual- are manifest, and it is for this reason that khat has been called a narcotic drug, but it is not so addictive as morphine. When the British, from one day to the next, strictly prohibited the use of khat in British Somaliland, no organic disorders were observed among the Aberahoual.

The use of khat removes the sensation of hunger, and this explains why most khat consumers are so thin.

Consequently, both from the sexual and intellectual points of view, and also from that of nutrition, khat may be regarded as a sort of social scourge. It causes the degeneration of the race in several respects, and work. becomes increasingly distasteful to the khat chewer. Thus, although not poisonous in itself, khat must be regarded as a poison by reason of the consequences of its consumption.

The question now is whether the use of khat should or should not be prohibited. Opinions are divided. From the human and social points of view; as has been said above, it is a sort of scourge which should be eliminated, at least gradually.

From the economic point of view, so far as French Somaliland is concerned, it is obvious that the 10 million fr which the sales tax on khat yields annually are not to be scorned.The consumption of khat accounts for an annual sum of 170 million Djibouti fr; the Ethiopians charge a tax of 160 fr ($2) per k, and the French a special tax of 35 fi: plus excise duty of 30 fir payable on the arrival of the daily aircraft from Addis Ababa, or at Ali-Sabieh, where the Franco-Ethiopian railway crosses the frontier.

In addition, there is the illicit traffic, which amounts to approximately 10% of the lawful trade.

On the other hand, as Mr. Roche, the former Procureur de la République at Djibouti, said, since the oriental is very fond of this narcotic, it is not impossible that an even more harmful substance might make its appearance, if khat were prohibited.