In vitro and in vivo transport of lithium by human erythrocytes.

An in vitro system that can be used to measure both uptake and efflux of lithium by erythrocytes (RBCs) is described. Using this system, RBC lithium accumulation in vitro was compared with in vivo RBC lithium concentrations observed in 6 normal volunteers. A significant correlation was demonstrated between in vitro RBC lithium accumulation after 48-hr incubation and in vivo RBC lithium concentration at 24, 48, 72, and 96 hr following the beginning of lithium ingestion. In addition, when efflux of lithium from RBCs in vitro was studied, a significant correlation was observed between residual lithium in RBCs and in vitro RBC lithium accumulation. Finally, it has been demonstrated that storage of blood in ice for 5 hr prior to incubation with lithium results in increased RBC lithium accumulation. A potential role for this in vitro incubation system as a model for in vivo RBC lithium accumulation is suggested.

Adjustment of lithium dose during lithium-chlorothiazide therapy.

There has been a long-held belief that lithium salts cannot be used in the presence of thiazide diuretics. Recently, however, thiazides have been demonstrated to be not only safe, but actually indicated in two situations in which lithium salts are used. The first is in the treatment of lithium-induced nephrogenic diabetes insipidus and the second is in severe manic depressive illness in which high doses of lithium do not produce therapeutic serum or intraeythrocytic lithium concentrations. This new information now makes it possible for some manic depressive patients with serious medical illnesses (such as hypertension or congestive heart failure), in whom thiazide diuretics are routinely used, to be treated cautiously with lithium carbonate. This paper analyzes data from 13 patients taking lithium carbonate and varying doses of chlorothiazide in order to indicate the approximate magnitude of downward adjustment of daily lithium dose which the clinician must make to safely give 500, 750, and 1,000 mg/day of chlorothiazide.

Pharmacokinetics of oral and transdermal triprolidine.

In this open, nonrandomized, three-way crossover study, six healthy male volunteers received single doses of triprolidine (TPL) hydrochloride syrup orally (2.5 mg) and wore transdermal TPL patches (5 mg and 10 mg doses) to compare the pharmacokinetic profiles and dose tolerance of the two formulations. A washout period of at least 1 week was scheduled between the three dosing periods. Blood samples were collected at defined times, and plasma concentrations were determined using a radioimmunoassay. Maximum plasma drug concentration (Cmax) decreased from 5.6 +/- 2.9 ng/mL (mean +/- SD) with oral dosing to 2.0 +/- 1.0 ng/mL and 4.2 +/- 2.0 ng/mL following 5 mg and 10 mg transdermal doses, respectively. Time to reach peak concentration (tmax) increased from 2.0 +/- 1.2 hours with oral dosing to 12.0 +/- 5.9 and 14.3 +/- 9.9 hours following 5 mg and 10 mg transdermal doses, respectively. The differences between AUC0-alpha values with the oral syrup and the 5 mg and 10 mg transdermal doses were not significant when normalized to 2.09 mg (TPL base). The bioavailabilities of the 5 mg and 10 mg transdermal doses relative to the oral 2.09 mg doses were 0.89 +/- 0.32 and 1.04 +/- 0.33, respectively. Mild erythema and pruritus were the most common adverse effects secondary to TPL transdermal application. Drowsiness observed following oral TPL, was not evident following either transdermal dose. The results of this study, therefore, indicate that TPL can be absorbed transdermally, providing consistent plasma concentrations.

Measurement of pseudoephedrine hydrochloride dissolution using chloride-ion electrode.

Experiments were performed to determine the suitability of using a chloride-ion electrode for the measurement of pseudoephedrine hydrochloride dissolution from commercially available compressed tablets. Dissolution experiments were carried out in 500 ml of distilled water using the USP paddle method at 100 rpm. Both chloride ion and pseudoephedrine (UV spectrophotometry) were measured at six different sampling times. Percent dissolved versus time values were linearized on a log-normal probability basis. The slopes of individual lines obtained from the chloride and pseudoephedrine measurements were compared using a Student t test and did not differ significantly (t = 0.415, df = 5, p greater than 0.05). In addition to providing an efficient, inexpensive, and simple method for measuring pseudoephedrine hydrochloride dissolution rates, the chloride-ion electrode could be used in the measurement of dissolution rates for a wide variety of drugs available as hydrochloride salts.

Correlation of quinidine absorption with disintegration and dissolution rates.

The dissolution profiles of four commercial quinidine sulfate tablets were determined using the USP rotating-basked dissolution apparatus. Substantial differences in dissolution half-times were noted and compared to previously reported disintegration times, absorption rate constants, and times of appearance of peak serum concentrations. Rank-order correlations were observed among all combinations of in vivo and in vitro parameters, indicating that the absorption rates of these tablets are controlled by both disintegration and dissolution.

In vivo-in vitro correlations for trisulfapyrimidine suspensions.

A UV method is described for measuring total sulfa drug concentration in dissolution samples. This in vitro measurement was found to correlate well with several in vivo parameters obtained after administration of commercial trisulfapyrimidine suspensions to humans. The UV method, which is rapid, simple, inexpensive and easily automated, is recommended for studying the dissolution of trisulfapyrimidine suspensions.

Bioequivalency of doxycycline products.

The bioavailability of three different brands and three different dosage forms of doxycycline was studied in normal subjects. Single doses, equivalent to 200 mg of doxycycline, were administered to six subjects in a crossover design as the innovator's intravenous solution given orally (Treatment A), the innovator's capsule product (Treatment B), a noninnovator's capsule product (Treatment C), the innovator's oral suspension product (Treatment D), and a second noninnovator's capsule product (Treatment E). All dosage forms contained doxycycline as the hyclate, except the suspension which contained the nonhyclate form. Serum levels were determined periodically over 48 hr, and cumulative urinary excretion was measured concurrently over a 120-hr collection period. No statistically significant differences were observed in any in vivo indicator of bioequivalence when the three capsule products were compared. Consequently, they were judged to be bioequivalent. When these capsule products were compared to the oral solution, no statistically significant differences were observed. However, when the capsules and the suspension were compared, statistically significant differences were found in the rate of absorption. In vitro dissolution tests were also conducted on the three brands of capsules, and times required to achieve 50% dissolution showed rank-order correlation with corresponding absorption rate constants.

Comparative bioavaiability of four commercial quinidine sulfate tablets.

A comparative bioavailability study was performed using four commercially available, chemically equivalent brands of quinidine sulfate tablets. Two 200-mg tablets were administered to 11 different subjects following a completely randomized crossover design. Serum levels, urinary excretion data, and derived pharmacokinetic parameters were compared statistically. There were no statistical differences in the extent of quinidine absorption from the four brands of tablets as evidenced by the cumulative urinary excretion values and the areas under the serum level-time curves. Significant differences in the mean serum levels at 0.5 and 1 hr and differences in the peak times and absorption rate constants indicate that there was a difference in the absorption rate between Treatments A and D and C and D. A significant difference in the peak times also was noted for Treatments B and C. When mean disintegration times for the four tablet formulations were compared with their values for ka, tmax and mean serum levels at 0.5 and 1 hr, rank-order correlations were observed. A considerable degree of variability in quinidine elimination was noted, with half-life values ranging from 2.71 to 8.12 hr (mean half-life of 5.36 hr).

Bioavailability and dissolution behavior of trisulfapyrimidine suspensions.

The bioavailability of seven commercial trisulfapyrimidine suspensions was studied in 14 adult male volunteers. Fifteen blood samples were collected over a 48-hr period following administration of a 1-g dose of each suspension. Serum was assayed for each component (sulfadiazine, sulfamerazine, and sulfamethazine) by high-pressure liquid chromatography. Analysis of variance indicated several significant differences among the seven commercial preparations with respect to Cmax Tmax, and AUC for sulfadiazine, sulfamerazine, and sulfamethazine, The in vitro behavior of each suspension was then studied by the paddle method of the Food and Drug Administration. A 0.5-ml sample was introduced into 900 ml of hydrochloric acid (2.2 x 10(-4) M) at 37 degree and dissolved using a paddle speed of 25 rpm. Samples withdrawn at 15 and 30 min were analyzed by high-pressure liquid chromatography, and the percent of sulfadiazine, sulfamerazine, and sulfamethazine was calculated. Significant correlation was obtained between an in vivo parameter (Cmax for sulfadiazine) and an in vitro parameter (percent sulfadiazine dissolved in 30 min). Results indicate that this method is suitable for the in vitro screening of trisulapyrimidine suspensions.

Simple high-pressure liquid chromatographic determination of trisulfapyrimidines in human serum.

A simple and rapid high-pressure liquid chromatographic method was developed for the determination of sulfadiazine, sulfamerazine, and sulfamethazine in human serum. After the trichloroacetic acid precipitation of the serum proteins, an aliquot of the supernate is injected into a high-pressure liquid chromatograph equipped with a reversed-phase microparticulate column and a fixed wavelength UV detector. For each of the three components of trisulfapyrimidines, a linear calibration curve was observed in the 1-30-microgram/ml range, with the precision of the assay estimated to be +/- 2% (RSD). Preliminary pharmacokinetic data are also presented.

Bioavailability of sulfonamide suspensions I: Dissolution profiles of sulfamethizole using paddle method.

A comparative bioavailability study was performed using two commercially available, chemically equivalent brands of sulfamethizole suspension. One gram of each suspension was administered to 12 different subjects following a completely randomized crossover design. Serum levels and derived pharmacokinetic parameters were compared statistically. There were no significant differences in the extent of sulfamethizole absorption from the two suspensions as evidenced by the area under the serum level--time curves. Significant differences (p less than 0.05) in the mean serum levels at 0.5 and 0.75 hr and differences in Cmax and tmax indicated that the absorption rate differed for the two products. In vitro tests including particle-size analysis and dissolution studies were performed. The size--frequency distribution of particles in the suspensions was studied using a resistance particle counter. The dissolution characteristics of the two products were studied using the Food and Drug Administration's paddle method and the spin-filter apparatus. Suspension A had a significantly greater amount of drug dissolved at 15 and 30 min using either method. It also had a greater percentage of particles at the smaller size range, indicating that the greater dissolution rate may be related directly to the decreased particle size. A comparison of the in vivo and in vitro results demonstrated a definite rank-order correlation between the dissolution performance of the two suspensions and the in vivo parameters reflecting the absorption rate. Suspension A had a greater amount of drug dissolved at 15 and 30 min and resulted in higher serum levels at 0.5 and 0.75 hr, a higher Cmax, and a shorter tmax.

OK-432 therapy for lymphangiomas.

OBJECTIVE: To assess the efficacy of OK-432 sclerotherapy in the treatment of lymphangiomas. DESIGN: Nonrandomized trial; follow-up, 4 to 29 months. SETTING: Academic tertiary referral medical center. PATIENTS: Six children with presumed lymphangiomas; age range at initial treatment, 1 month to 7 years 10 months. INTERVENTION: Fluoroscopically guided cyst aspiration, cystography, and injection of OK-432. OUTCOME MEASURES: Clinical and radiographic comparisons before and after therapy. RESULTS: Complete response in 2 macrocystic lymphangiomas; no response in 3 microcystic lymphangiomas; and no response in 1 venous malformation. CONCLUSION: OK-432 sclerotherapy may be effective treatment for macrocystic lymphangiomas.

Treatment of lymphangiomas in children: an update of Picibanil (OK-432) sclerotherapy.

Picibanil (OK-432) is a sclerosing agent derived from a low-virulence strain of Streptococcus pyogenes that induces regression of macrocystic lymphangiomas. This report describes a prospective, nonrandomized trial to evaluate the efficacy of Picibanil in the treatment of 13 affected children ranging in age from 1 to 94 months. On average, 4.1 fluoroscopically guided intracystic injections were performed per child, with an average total dose of 0.56 mg of Picibanil. As judged by physical examination and radiographic studies, 5 children (42%) showed a complete or substantial response, and 2 children (16%) showed an intermediate response. No response was seen in 5 children (42%), 2 of whom had massive craniofacial lymphangioma. Factors that contribute to failure with Picibanil sclerotherapy are the presence of a significant microcystic component to the lesion, massive craniofacial involvement, and previous surgical resection. Macrocystic lymphangiomas of the infratemporal fossa or cervical area have the best response to therapy.