Thymoxamine hydrochloride: an alpha-adrenergic blocker

Thymoxamine is an alpha-adrenergic blocking agent which works by competitive antagonism of norepinephrine. It is the only alpha-adrenergic blocker available which has tolerable side effects when used as an ophthalmic solution. When used as a 0.5% solution it consistently produces miosis without affecting the intraocular pressure or the ciliary muscle-controlled facility of outflow. The only regularly reported side-effects at this concentration are transient burning and conjunctival hyperemia. Potential applications of thymoxamine include reversal of phenylephrine mydriasis, treatment of angle-closure glaucoma, treatment of persistent mydriasis after penetrating keratoplasty for keratoconus, reversal of lid retraction in thyroid ophthalmopathy, testing to differentiate angle-closure glaucoma from open-angle glaucoma with narrow angles, aiding in repositioning and maintaining the position of intraocular lenses, treatment of pigmentary glaucoma. Thymoxamine may also contribute to a better understanding of the adrenergic nervous system on aqueous dynamics.

The effects of thymoxamine on anterior chamber depth in human eyes

The effects of 0.5% Thymoxamine on intraocular pressure and anterior chamber depth were studied in 20 non-glaucomatous eyes. Miosis occurred in all of the eyes but was not accompanied by a shallowing of the anterior chamber or reduction in the intraocular pressure. The significance of the findings is discussed.

Actions and metabolism of codeine (methylmorphine) administration by continuous intravenous infusion to humans

Miosis produced by codeine is not antagonized by nalorphine until large oral doses are administered for several days. The present experiment was conducted in order to further study this characteristic of the codeine effect. Eight healthy male volunteers, who were former drug users, were divided into two groups. Subjects in the first group were given a continuous infusion of codeine, 30 mg/hr for 11-16 hr. No subjective effects were reported by the volunteers. In three of the individuals definite miosis antagonized by nalorphine was observed at 9.5 hr. The dose of codeine for the second group was 60 mg/hr for 11 hr. Mild but definite subjective effects were experienced by each of the participants in this group. Miosis appeared between 2 and 6 hr. Challenges at 4 and 6 hr were positive in two subjects and negative or equivocal in the other two. Codeine was excreted in the urine as free and conjugated codeine, morphine, and norcodeine. Maximum rates of excretion were similar for both groups, suggesting that the maximum amount of codeine that can be metabolized is equal or less than 30 mg/hr. Also codeine clearance, being greater than creatinine clearance, suggests that codeine might be excreted by glomerular filtration and tubular secretion. Blood levels of codeine in the 60 mg/hr group were about 10 times those reported as therapeutic. However, morphine or norcodeine were not detectable by the methods used.

[Clinical experience with r30730/Janssen in anaesthesia for ophthalmic surgery (author's transl)]

Fentanyl was replaced by R 30730/Janssen (Fentatienyl) for neurolept analgesia (with intubation) of 34 persons who had ophthalmic surgery on account of detachment of the retina. The effects of the drug on the size of the pupils, blood pressure, heart rate and respiration were observed; also the duration of analgesia and the incidence of nausea and vomiting. There was a very slight negative effect on the size of the pupil, similar to that seen with halothane; systolic blood pressure fell by an average of 20%; the duration of analgesia and the degree of respiratory depression varied considerably. 12 of the 35 patients suffered from marked nausea and vomiting after the operation.

Pharmacokinetics of chlorpromazine-induced miotic response in rabbits

The time variation of changes in the chlorpromazine-induced pupil diameter decrease was studied following varying bolus and slowly infused intravenous doses administered to rabbits. The observed pharmacological response data were coverted, via, the use of a dose-effect curve, to values theoretically corresponding to relative biophasic drug levels. These values were, in turn, used to construct a linear pharmacokinetic model of the drug bioavailability input equilibrium pharmacological response output dynamics of the system. The use of a time domain, MULTIFIT, computerized method of fitting the data to obtain a pharmacokinetic model was compared to the use of a frequency response, PLTEST, approach. The fidelity of the model in quantitatively relating the time course of systemic drug bioavailability to observed pupil response was verified by the satisfactory agreement obtained by directly comparing experimentally known amounts of drug intravenously infused with corresponding values computed from observed changes in pupil size. The applicability of using pharmacological data for quantitative bioavailability and pharmacokinetic analysis of chlorpromazine is demonstrated. This finding is particularly significant because no suitable chemical or radiological direct assay technique exists for determining levels of chlorpromazine, except for high doses, in body fluids.

Hypotension and bradycardia following intraocular acetylcholine injection. Report of a case

A possible systemic reaction to acetylcholine chloride injected into the anterior chamber of the eye occurred in a 65-year-old patient who had a cataract extraction while under general anesthesia. Following cataract extraction, 20 mg of acetylcholine chloride was injected into the anterior chamber of the eye. Immediately following injection, hypotension and bradycardia (48 beats per minute) occurred.

Azidomorphine: subjective effects and suppression of morphine abstinence

In man, azidomorphine, a new morphine congener, constricted pupils, produced morphine-like subjective effects and euphoria, and suppressed the morphine abstinence syndrome. Azidomorphine was 10 to 50 times as potent as morphine. It is concluded that in man azidomorphine is a typical morphine-like drug.

Meiosis: a prostaglandin response that is not inhibited by aspirin

Antidromic stimulation of the sensory nerve to the rabbit eye produces pupillary meiosis, supposedly by release of prostaglandins into the aqueous humour. The analogy between this phenomenon and neurogenic inflammation is drawn. It is shown that aspirin and indomethacin, known blockers of prostaglandin synthesis and release, fail to block the meiosis thus produced.