Mydriasis drug-induced

Parasympatholytics are used to induce a mydriasis in the ophthalmology for the examination of the retina. They are applied locally as drops or ointment. The drug-induced inability of the eyes to accommodate results in a serious, although transient, impairment of the visus. Therefore the long-acting atropine (7-10 days) is replaced by short-acting compounds like homatropine (1-3 days), cyclopentolate (1 day) or tropicamide (6 hours). 

Pupil Examination. A meaningful evaluation of pupils after drug-induced mydriasis or miosis is impossible. Pupillary examination, including pupil size and responsiveness, should be undertaken before instilling mydriat-ics or miotics.The presence and nature of direct reflexes as well as the presence or absence of a relative afferent pupillary defect should be recorded. 

Trihexyphenidyl is contraindicated in patients with narrow-angle glancoma becanse drug-induced cycloplegia and mydriasis may increase intraocnlar pressure in patients with cardiac disorders, arteriosclerosis, renal disorders, hepatic disorders, hypertension, obstructive G1 or genitourinary tract disease, or snspected prostatic hypertrophy becanse the drug may exacerbate these conditions. 

Medications with anticholinergic properties induce mydriasis, which can lead to angle closure in pupillary block and plateau iris. Pupillary block may also be induced by drugs that cause miosis.12... 

The elation and euphoria that cocaine induces in susceptible individuals tend to render it a habit drug, but it is more apt to be used for occasional jags, by criminals, rather than daily, as is morphine. The treatment is therefore easier and more likely to be successful. However, it may be used continuously as it was by the South American natives in India, it is combined with the chewing of betel leaf. Cocaine inebriation is active and sociable, in contrast to the dreamy state induced by morphine. It may also induce a more or less maniacal condition, in which the individual becomes dangerous to others. The immediate effects include the phenomena of sympathetic stimulation, resembling hyperthyroidism tachycardia, polypnea, mydriasis, exophthalmos, and fine tremors. Some individuals, especially women, react with marked erotic excitement. The stimulation is succeeded by depression, tremors, pallor, and sunken and unsteady eyes. 

At higher concentrations, atropine causes block of all parasympathetic functions. However, atropine is a remarkably safe drug in adults. Atropine poisoning has occurred as a result of attempted suicide, but most cases are due to attempts to induce hallucinations. Poisoned individuals manifest dry mouth, mydriasis, tachycardia, hot and flushed skin, agitation, and delirium for as long as a week. Body temperature is frequently elevated. These effects are memorialized in the adage, "dry as a bone, blind as a bat, red as a beet, mad as a hatter."... 

Sympathomimetic agents, such as brimonidine tartrate, apraclonidine, adrenaline and dipivefrine hydrochloride, which is a prodrug for adrenaline), act on a-adrenoreceptors to induce dilation of the veins to reduce IOP. They also induce mydriasis (dilation of the pupils). Adrenaline may reduce the rate of formation of the aqueous humour, which in turn reduces the IOP it may also increase the outflow through the trabecular meshwork. Stimulation of alpha-2-adrenoreceptor (c -adrenoreceptor) by drugs such as brimonidine and apraclonidine on the adrenergic neurons supplying the ciliary body can also result in reduction of secretion of aqueous humour. 

Among the drugs most commonly implicated are the sulfonamides. Two cases of transient myopia associated with oral sulfonamides were described in which there was reduced accommodation, shallow anterior chamber angles, and moderate mydriasis. Chemosis occurred in one case. A 23-year-old woman was described who had 4.00D of increased myopia in one eye and 3.00D of increase in the fellow eye after the use of oral sulfonamides. Vaginal absorption of sulfonamides can also lead to myopia. A patient was reported with 1.00 to 1.50D of myopia after use of a vaginal sulfonamide suppository and another patient with 7.00D of induced myopia after use of a sulfonamide vaginal cream. 

Glutethimide (250 to 500 mg at bedtime) is indicated in short-term (a few days) relief of insomnia. It exhibits pronounced atropine-like effects including mydriasis and inhibition of secretion and motility of the GI tract. Similar to barbiturates, glutethimide depresses the CNS and has addictive effects with alcohol and other CNS drugs. It depresses rapid-eye-movement (REM) sleep and is associated with REM rebound. Glutethimide induces the activity of hepatic microsomal enzyme and accelerates the metabolism of anticoagulants, and hence reduces their effectiveness, thus requiring dose adjustment. 

Epinephrine itself is not mydriatic when it is applied locally to the normal human eye, possibly because it is not sufficiently well absorbed from the conjunctival sac nor does epinephrine produce mydriasis when it is injected into man, unless the sympathetic fibers to the iris have degenerated (e.g., as the result of extirpation of the superior cervical ganglion) or the iris is sensitized by thyroxine, as in hyperthyroid patients. In experimental animals, however, drugs which induce a liberal outflow of epinephrine from the adrenal medulla do produce mydriasis. Epinephrine has therefore the capacity of dilating the pupil, but only when it can reach the site of action in sufficient concentration it must be concluded that local application of the drug does not enable this concentration to be achieved, and that the amounts of it which can be safely injected are also insufficient to effect mydriasis in patients with normal eyes. 

---