When taken internally it is both a secretory and an excretory cholagogue, but so irritant and powerful that its use in cases of jaundice is generally undesirable.
Many points in the development and mechanism of the nematocyst are disputed, but it is tolerably certain (I) that the cnidocil is of sensory nature, and that stimulation, by contact with prey or in other ways, causes a reflex discharge of the nematocyst; (2) that the discharge is an explosive change whereby the in-turned thread is suddenly everted and turned inside out, being thus shot through the opening in the outer wall of the capsule, and forced violently into the tissues of the prey, or, it may be, of an enemy; (3) that the thread inflicts not merely a mechanical wound, but instils an irritant poison, numbing and paralysing in its action.
If it be absorbed from a surgical dressing there are no irritant symptoms, but when the acid is swallowed in concentrated form, symptoms of gastro-intestinal irritation occur.
Colchicum or colchicine, when applied to the skin, acts as a powerful irritant, causing local pain and congestion.
In larger doses colchicum or colchicine acts as a most violent gastrointestinal irritant, causing terrible pain, colic,vomiting, diarrhoea, haemorrhage from the bowel, thirst and ultimately death from collapse.
Salicylic acid is a powerful irritant when inhaled or swallowed in a concentrated form, and even when much diluted it causes pain, nausea and vomiting.
When salicin is taken internally no irritant action occurs, nor is there any antisepsis.
The irritant may be chemical, as is seen in the skin cancers that develop in workers in paraffin, petroleum, arsenic and aniline.
The salt is a corrosive irritant poison when taken internally.
Thoroughly rubbed into the skin alcohol dilates the bloodvessels and produces a mild counter-irritant effect.
Though ammonium chloride has certain irritant properties which may disorder the stomach, yet if its mucous membrane be depressed and atonic the drug may improve its condition, and it has been used with success in gastric and intestinal catarrhs of a subacute type and is given in doses of io grains half an hour before meals in painful dyspepsia due to hyperacidity.
Though, as Lacaze-Duthiers remarks, a certain relation is necessary between the " stimulus " and the " supporter of the stimulus," as evidenced by the limitation in the majority of cases of each species of gall-insect to some one vegetable structure, still it must be the quality of the irritant not strictly obsolete, is now seldom used; the formation is felt to be somewhat uncouth, so that the use of the word in the plural in commonly evaded " (New Eng.
Externally: Caustic potash is a most powerful irritant and caustic; it is used with lime in making Vienna paste, which is occasionally used to destroy morbid growths.
The permanganate of potash is an irritant if used pure.
It possesses the advantage of exercising but little irritant effect upon the bowels.
Recent work has shown it is too feeble to be relied upon alone, but where really efficient antiseptics, such as mercuric chloride and iodide, and carbolic acid, have been already employed, boracic acid (which, unlike these, is non-poisonous and non-irritant) may legitimately be used to maintain the aseptic or non-bacterial condition which they have obtained.
The British Pharmacopoeia contains a watery solution - the Aqua Chloroformi - which is useful in disguising the taste of nauseous drugs; a liniment which consists of equal parts of camphor liniment and chloroform, and is a useful counter-irritant; the Spiritus Chloroformi (erroneously known as "chloric ether"), which is a useful anodyne in doses of from five to forty drops; and the Tinctura Chloroformi et Morphinae Composita, which is the equivalent of a proprietary drug called chlorodyne.
The uses of chloroform which fall to be mentioned here are: - as a counter-irritant; as a local anaesthetic for toothache due to caries, it being applied on a cotton wool plug which is inserted into the carious cavity; as an antispasmodic in tetanus and hydrophobia; and as the best and most immediate and effective antidote in cases of strychnine poisoning.
The drug is described as a counter-irritant, though the explanation of this action is very doubtful.
Cantharides is used externally for its counter-irritant action.
Thus irritation of the eye causes winking and secretion of tears, by which the irritant is removed; irritation of the nose causes sneezing; of the air-passages, coughing; of the stomach, vomiting; and of the intestines, diarrhoea.
For inflammation of the mouth a similar combination is used as a mouth wash, in the throat as a gargle, and in the nose as a wash and sometimes as an ointment or spray, the ointment possessing the advantage of protecting the delicate nasal mucous membrane from irritation by stopping the entrance of irritant dust into the nasal cavities.
After the irritant has been removed either from the stomach or intestine, a feeling of irritation of the mucous membrane may remain, and sickness, diarrhoea or pain may continue in the stomach and intestine although the irritant is no longer present within them, just as the flow of tears and desire to rub may remain in the eye after the piece of grit which has occasioned it may have been removed.
The condition which remains after the irritant has been removed is one of inflammation more or less intense.
By preventing fermentation in the intestine these also tend to prevent or check diarrhoea, and they may do good after the irritant has been removed by castor oil.
After the irritant has been removed and fermentation stopped, the irritation still remaining in the intestinal wall may be soothed by chalk mixture and bismuth, to which if necessary small quantities of opium may be added.
Summed up, its action is that of an irritant, and a cardiac and nervous depressant.
In some abdominal conditions, for instance, opium is still preferred by the majority of practitioners, though certainly not in gastric cases, where morphine gives the relief for which opium often increases the need, owing to the irritant action of some of its constituents.
Quinine does not affect the unbroken skin, and cannot be absorbed from it, but it is slightly irritant to the pain-conducting nerves of a raw surface.