Practice tip. Which cerumenolytic?

AIM: To test the in vitro dispersion of ear wax by four commonly used cerumenolytics. METHOD: Equal parts of the same piece of ear wax were covered with 10 mL of each preparation and observed for up to 30 days. RESULTS: Sodium bicarbonate and Waxsol dispersed wax within 2 hours, Cerumol was much slower and olive oil had no effect. CONCLUSIONS: The cheapest and most effective cerumenolytic is a solution of sodium bicarbonate.

Total bilirubin level in relation to excipients in parenteral morphine sulfate administered to seriously ill newborn infants.

We examined exposure to excipients in different morphine sulfate preparations in relation to maximum total bilirubin level during the first 5 days of life among 155 infants admitted to a newborn intensive care unit. Sixty-six (43%), 47 (30%), and 42 (27%) newborns were exposed to chlorobutanol, phenol and neither excipient, respectively. Mean maximum total bilirubin in the first 5 days of life among newborns not exposed to chlorobutanol or phenol was 10.8 mg/dL (184 mumol/L). After adjusting for birthweight, race, sex, and use of phototherapy, the maximum total bilirubin level among newborns exposed to phenol was 1.4 mg/dL (24 mumol/L) higher than the maximum level among newborns exposed to neither excipient (P < 0.05); the corresponding difference associated with chlorobutanol exposure was 1.6 mg/dL (27 mumol/L) (P < 0.02). Further adjustment for potential confounding by the major risk factors for hyperbilirubinaemia did not materially change the results. While unconfirmed, these findings support the growing concern that excipients added to parenteral medications may not be 'inactive' as is often assumed, and that the safety of such exposures in seriously ill newborn infants needs to be studied further.

An in vitro study to determine efficacy of different wax-dispersing agents.

An in vitro study was performed to compare the relative efficacy of a number of aqueous- and organic-based wax-dispersing preparations. Water, which was originally intended to be a control, surprisingly proved to be the most effective, whilst olive oil appeared to be almost totally ineffective as a wax dispersant. In view of the relatively high cost of commercially available preparations, these results have significant clinical potential.

The mechanism of ceruminolysis.

In a previous study comparing the efficacy of a selection of commonly used ceruminolytics, the authors noted that aqueous-based preparations, and in particular solutions of sodium bicarbonate, were more effective in disintegrating cerumen than most organic-based preparations. In that study, the authors also observed that not only had the wax truly disintegrated following exposure to the aqueous-based preparations, but also that a marked degree of swelling of the wax spheres had occurred with these preparations. In this paper the mechanism of ceruminolysis was investigated by means of a number of commonly available histological techniques. Our findings show that desquamated sheets of corneocytes are the major constituent of cerumen plugs and provide the structural framework of the wax bolus. Ceruminolytics work by hydrating the keratin cells of these sheets of desquamated stratum corneum and subsequently inducing keratolysis, with disintegration of the wax.

Lack of effects of d-tubocurarine and pancuronium on the slow action potential of the guinea pig papillary muscle.

Inotropic effects of non-depolarizing muscle relaxants were examined with guinea pig ventricular papillary muscle depolarized to -47 mV in high K Ba-Tyrode solution. Field stimulation of 0.1 Hz elicited the slow action potential, a measure of the calcium current. The amplitude, the duration at 0 mV level and dV/dt of the action potential were monitored together with the contractile tension. Amelizol (3 mg X ml-1 d-tubocurarine (d-tc) and 5 mg X ml-1 chlorobutanol) depressed the four functions in a dose-dependent manner, while crystalline d-tc did not. Chlorobutanol (the antimicrobial preservative) had the same effects as Amelizol. Neither Mioblock (2 mg X ml-1 pancuronium and unpublished preservative) nor crystalline pancuronium altered the functions. These findings suggest that the negative inotropic effect of Amelizol is not due to d-tc but to chlorobutanol, which may exert its effect by depressing the calcium current. The lack of change in the slow action potential seen with pancuronium may indicate no direct effect on the calcium current, thereby further suggesting absent direct beta-adrenomimetic action of this agent.

Impairment of ascorbic acid synthesis in liver extracts of magnesium-deficient rats.

The effect of feeding a magnesium (Mg)-deficient diet for 9-34 days to weanling and young male rats on urinary and tissue ascorbate levels were studied. The concentrations of ascorbic acid in the liver and kidney were significantly reduced in the rats receiving a Mg-deficient diet as compared to those receiving a Mg-supplemented diet. The response to trichloro-2-methyl-2-propanol stimulation of urinary ascorbic acid was found to be considerably suppressed by dietary deficiency of Mg, suggesting that the decrease was not due to feed intake. In in vitro studies, the enzymatic synthesis of the vitamin from glucuronolactone or gulonolactone by liver extracts from Mg-deficient rats was significantly decreased as compared with Mg-supplemented rats. These results suggest that Mg-deficient rats have a reduced capacity to synthesize ascorbate which in turn produces a decrease in ascorbic acid concentrations in the liver.

Effects of ethionine feeding on urinary and tissue ascorbic acid concentrations in rats.

The effect of feeding 0.25% ethionine for 3-10 weeks to male and female rats on urinary and tissue ascorbate contents were studied. The concentrations of ascorbic acid in the urine, blood, liver and adrenals were significantly reduced in the rats receiving ethionine as compared to those receiving stock diet. This decrease was not apparently due to feed intake, not reversed by supplementation of methionine, but can be partially restored by removing ethionine from stock diet. The response to trichloro-2-methyl-2-propanol stimulation of urinary ascorbic acid was considerably suppressed by ethionine administration. In vitro the enzymatic synthesis of the vitamin from glucuronolactone by liver homogenate of ethionine-fed rats was significantly decreased from that of stock diet-fed controls. These results indicate that ethionine reduces the capacity to synthesize ascorbate which, in turn, causes a decrease of ascorbic acid contents in the urine, blood, liver and adrenals.