Saturated solutions of iodoforrn in ether become, as the point of saturation is reached, very unstable, and under the influence of the slightest causes they are decomposed suddenly, a reddish color re sembling that of tincture of iodine re sulting. The decomposition is rendered less rapid if the solutions are less con centrated. In saturated ethereal solu tions it may be retarded by the addition of alcohol and by keeping them protected from sunlight.
The ointment of iodoform (U. S. P.) contains 10 per cent. of the drug.
Physiological Action.—Iodoform con taining about 29 parts of pure iodine in 30, the carbon and hydrogen with which it is associated render the iodine non irritant, either when taken by the mouth or applied topically. It is markedly anaes thetic when locally applied, owing to a benumbing influence upon the peripheral nerves. Defecation may follow the use of iodoform suppositories, and not be felt by the patient.
Iodoform tends to decrease the energy of cardiac contractions and reduces the number of pulsations. When toxic doses are administered the contractions become gradually weaker and the heart ceases its work in diastole. The action begins upon the nerve-trunks, then extends to the muscles. There is alteration of the blood-corpuscles, according to Floucaud.
Rummo has shown that the elimina tion of iodoform is extremely slow, though it begins soon after its ingestion. It leaves the organism by all the secre tions and iodine may still be found in the urine three days after the iodoform is employed.
In dogs poisoned by iodoform Kori andere found inflammation of the glom eruli of the kidney and fatty infiltra tion of the liver, principally around the periphery of the lobules. In chronic cases he found, besides these changes, ex treme emaciation, general anaemia, puru lent bronchitis, rhinitis, conjunctivitis, and accumulation of pigment in the Mal pighian bodies.
Untoward Effects of Iodoform.—Re cently Hubener has shown that no essen tial difference in the toxic effects of finely powdered or coarse crystals of iodoform can be established by experi mental research. Still, powdered iodo form is more quickly absorbed and dif fused by the lymph-channels than the coarser form.
Experiments in animals have shown that, when used in the peritoneal cavity, iodoform has a distinct tendency to pro duce an inflammatory process, resulting in an excessive formation of adhesions. Consequently its use under such condi tions should be restricted, and the sterile gauze employed whenever feasible.
Crystals of iodoform have been found to a large extent to become converted by the action of the tissues into minute vesicle-like granules. Prior to its ulti mate breaking up into its chemical com ponents, it undergoes a change into com plicated iodine compounds, whose exact nature as yet remain unknown.
Many of the untoward results observed during the use of iodoform arc due to impurities. In order to test the purity of iodoform, a practical plan is to shake a portion up with distilled water, filter, and treat the liquid with alcoholized solu tion of nitrate of silver. If in twenty four hours no precipitate occurs, or only a slight grayish cloudiness, the iodoform may be regarded as pure.
When iodoform is employed, the use of mercurials should be avoided. Its use along with carbolic acid is also fraught with danger.
Mercurous iodide poisoning resulting from the use of iodoform as a surgical dressing and calomel internally. son (Amer. Jour. of Obstetrics, Apr., '98). The local symptoms due to iodoform are generally insignificant erythematous erosions, erysipelas, or simulated mon, especially affecting the finer tions of the skin, as the face, eyelids, scrotum, etc. The conjunctiva, however, appears to be tolerant of the drug, and the eruptions are rarely observed in dren. The local lesions are almost always due to the use of the powder and gauze. General symptoms may occur without any preceding local symptoms, the point of entrance being the stomach, lungs, or skin. Injections of iodoform-ether are rarely followed by accidents, though cer tain wounds predispose to such, espe cially those involving fatty tissue.
The clinical signs are a sudden rise of temperature (102.2° to 104° F.) and the appearance, on the same day or the fol lowing day, of an eruption, often of the scarlatiniform or erythematous type. In ternal symptoms may exist at the same time or alone, such as dislike for food, burning sensation in the epigastrium, vomiting, and nausea. All these phe nomena may be sufficiently severe to cause death. (Cheron.) What may be termed "surgical iodo formism" is sometimes met with. After a longer or shorter period of complete toleration the wound, while secreting no pus, is surrounded by an inflam matory area with development at its circumference of inflammatory vesicles (iodoformic herpes). Petechim appear near the wound or at a distance in patches or groups. The wound stagnates and inflames, but does not heal. A gen eralized pruritus along the collateral nerves of the fingers follows, succeeded by diffuse phlyctenulte. Areolar or pseudo erysipelatous lymphangitis appears in the affected limb. If the use of iodo form is persisted in lymphangitis pro gresses, the tongue becomes coated, and the patient is agitated and sleepless. A phlegmonous condition with general symptoms develops, and necrosis may threaten the patient with loss of limb or life. Tussau (Semaine Med., Nov., '96).