Once bitten, twice shy: concern about gaining weight after smoking cessation and its association with seeking treatment.

BACKGROUND: Concern about weight gain after quitting smoking is often cited as a barrier to smokers making a quit attempt or seeking treatment. AIM: To identify whether smokers who are non-treatment seekers (NTS) are more concerned about weight gain and have lower confidence to maintain weight after quitting smoking as compared with treatment-seeking smokers (TS). METHODS: Participants were smokers recruited from Penn State Hershey Medical Center and family practice outpatient clinics. A total of 102 NTS and 186 TS, who participated in a smoking cessation trial, completed a survey regarding tobacco use, weight concern and diet. Stepwise logistic regression was used to identify variables associated with treatment seeking, overall and stratified by those who gained and did not gain weight on a previous quit attempt. RESULTS: Fifty three per cent of the overall sample (47.1% NTS vs. 56.5% TS, p = 0.127) had gained weight on a prior quit attempt. Among smokers who had gained weight, higher weight gain concern (WGC) and lower confidence in ability to maintain weight were significantly associated with being a NTS after adjusting for other factors. CONCLUSION: Among smokers who gained weight on a previous quit attempt, NTS had greater concern about gaining weight and less confidence in their ability to maintain their weight after quitting than treatment seekers. Clinicians can identify smokers for whom WGC may be a barrier to seeking treatment by asking if they gained weight on a previous quit attempt. These smokers should be assured that this issue will be addressed in treatment.

Disposition of oral azithromycin in humans.

BACKGROUND: The oral bioavailability of azithromycin is approximately 37% in healthy subjects; little is known about the disposition of the remaining 63% of the dose. This study attempted to describe the fate of azithromycin before absorption. METHODS: Twelve subjects with ileostomies in place for > 1 month were studied in this open-label, randomized, three-center, two-period, two-treatment crossover study. Subjects randomly received single 500 mg intravenous infusion (over 1 hour) or two 250 mg oral capsules after a fast for > 12 hours. Blood and ileostomy samples were collected serially after each administration and analyzed for azithromycin and two metabolites (descladinose and 9a-N-desmethyl metabolites) by HPLC with electrochemical detection. RESULTS: Mean +/- SD peak concentration values after oral and intravenous administration were 0.21 +/- 0.08 and 3.40 +/- 1.12 microgram/ml. Mean values for area under the serum concentration versus time curve were 1.27 +/- 0.65 and 7.14 +/- 1.34 micrograms x hr/ml, respectively. The absolute bioavailability of 16.2% was approximately one-half the value observed previously in healthy subjects. Recovery in ileostomy fluid (percent of dose in 24 hours) or azithromycin, descladinose, and 9a-N-desmethyl metabolites were 13%, 0.5%, and 1% (total, 15%) after intravenous dosing and 47%, 13%, and 2% (total, 62%) after oral dosing. Total and ileal clearances were 776 +/- 126 and 158 +/- 63 ml/min after intravenous dosing. CONCLUSION: Because more descladinose metabolite was detected after oral dosing, acid degradation of azithromycin before absorption contributed to some loss in oral bioavailability. Further, ileal clearance (biliary plus intestinal excretion clearance) in this population represented 21% of total clearance. Taken together, these data suggest that the cause of low oral bioavailability of azithromycin is the result of incomplete absorption rather than acid degradation or extensive first-pass metabolism.

Sulbactam kinetics and excretion into breast milk in postpartum women.

We gave intravenous infusions of sulbactam, a beta-lactamase inhibitor, in combination with ampicillin or cephalothin to women 2 days after cesarean section delivery. The elimination t1/2 was 1.0 hours, the volume of distribution at steady state was 268 ml/kg, and renal clearance was 295 ml/min. These values are similar to those in normal young men and in surgical patients and suggest that dose regimens of sulbactam will not need adjustment in the postpartum period. Sulbactam concentrations in breast milk averaged 0.5 micrograms/ml, a value similar to that of several beta-lactam antibiotics.

Kinetics of an orally absorbed aldose reductase inhibitor, sorbinil.

Kinetics of sorbinil, an orally absorbed reductase inhibitor, were examined in man. Peak plasma concentrations were 0.95 micrograms/ml after a single 50-mg oral dose and 3.6 micrograms/ml after a 250-mg dose. The apparent volume of distribution was 840 ml/kg. Elimination from plasma was slow with a terminal half-life between 6 and 24 hr after dose of 34 to 52 hr and a renal clearance of 6.0 ml/min/1.73 m2. Administration of 50 mg/day for 5 days induced a mean peak serum concentration of 1.9 micrograms/ml. A dose of 250 mg/day for 10 days induced a peak serum concentration of 10.6 micrograms/ml. A mean of one-third of the dose was ultimately recovered unchanged in urine. Sorbinil kinetics make it suitable for once-a-day dosing.

Ocular uptake of fluconazole following oral administration.

The ocular penetration and distribution of oral fluconazole was studied in Dutch-belted rabbits. Measured by high-pressure liquid chromatography, fluconazole readily penetrated all ocular tissues and fluids. No difference was observed between the levels obtained in phakic and aphakic eyes. Four hours after a single oral dose of 20 mg/kg, the mean levels and SEs were as follows: cornea, 13.3 +/- 1.4 micrograms/g; aqueous, 7.4 +/- 0.3 mg/L; vitreous, 9.8 +/- 0.9 mg/L; and choroid/retina, 5.2 +/- 0.4 micrograms/g. These levels were approximately twice those obtained with a 10-mg/kg dose. The corneal concentrations correlated highly with serum levels (r = .89). A steady accumulation in both normal corneas and corneas infected with Candida albicans was noted when 17.5 mg/kg of fluconazole was administered twice daily over a 5-day period. Drug levels did not increase in the cornea when fluconazole was administered as a single daily dose of 35 mg/kg. In view of its excellent ocular pharmacokinetic profile, fluconazole merits further attention as an orally administered agent for ocular fungal infections.

Ocular levels of azithromycin.

OBJECTIVE: To assess azithromycin levels in human serum, aqueous humor, tear fluid, and conjunctival tissue specimens after administration of a single 1-g oral dose of azithromycin. METHODS: Sixty patients undergoing cataract surgery were included in this analysis. Serum, aqueous, and tear specimens were collected 3, 6, and 12 hours and 1, 2, 3, and 4 days after azithromycin administration. Conjunctival tissue biopsy specimens were collected 1, 2, 3, 4, 6, 8, 10, 12, and 14 days after azithromycin administration. All specimens were subjected to analysis by high-performance liquid chromatography-mass spectrometry. RESULTS: Azithromycin concentration ranges during the specified sampling times were as follows: serum, 21 to 974 ng/mL; tear, 82 to 2892 ng/mL; aqueous, 10 to 69 ng/mL; and conjunctival, 0.7 to 32 micrograms/g. Levels above the 90% minimal inhibitory concentration (MIC90) for Chlamydia trachomatis were detected after 4 days in all tear samples and after 14 days in all conjunctival tissue specimens following oral azithromycin administration. CONCLUSION: We demonstrated prolonged high levels of azithromycin in drug-targeted ocular tissue. Prolonged high concentrations of azithromycin in conjunctival tissue make this drug suitable for treatment of conjunctivitis caused by chlamydiae and other susceptible organisms.

A study of the pharmacokinetics of azithromycin and nelfinavir when coadministered in healthy volunteers.

A two-way, open-label, crossover study in 12 subjects was undertaken to study the potential for azithromycin to alter the pharmacokinetics of nelfinavir and/or its active metabolite, M8. A secondary objective was to characterize any potential interaction that nelfinavir may have with azithromycin. During one dosing arm, subjects received a single 1200 mg oral dose of azithromycin. During the other, subjects received 11 days of nelfinavir 750 mg q8h with a single 1200 mg oral dose of azithromycin given concurrently with the Day 9 morning nelfinavir dose. Serum samples were collected after each azithromycin dose for 168 hours and after the Day 8 and 9 morning nelfinavir doses for 8 hours to characterize azithromycin, nelfinavir, and M8 pharmacokinetic parameters during both control and test periods. Both dosing regimens were well tolerated, with only mild to moderate GI side effects being the most frequently reported. Azithromycin was found to cause a statistically, though not clinically, significant decrease in nelfinavir and M8 exposures. In contrast, nelfinavir caused azithromycin Cmax and exposure (AUC) values to increase by > 100%. Inhibition of p-glycoprotein by nelfinavir may be responsible for this significant interaction. This increase in azithromycin exposure has the potential to increase clinical antibacterial efficacy without significantly increasing gastrointestinal side effects, though the impact on other systemic sites needs to be studied.

The effects of an antacid or cimetidine on the serum concentrations of azithromycin.

The effects of an antacid and of cimetidine on the serum concentrations of azithromycin were examined in volunteers. Ten subjects were given 500 mg azithromycin alone and immediately after being given 30 mL Maalox (Rorer, Fort Washington, PA) in a crossover design. There were no statistically significant differences in Tmax or AUC0-48 after administration of azithromycin alone or with antacid, but mean values of Cmax were reduced by 24% (P = .015). Thus, although Cmax was decreased, the extent of absorption of azithromycin was not affected by coadministration with an antacid. Two groups of six volunteers were given 500 mg azithromycin on day 1. On day 8, one group was given 800 mg cimetidine 2 hours before a dose of azithromycin; the remaining group received placebo before azithromycin. There were no differences in the pharmacokinetic parameters produced by administration with cimetidine or placebo, relative to those on day 1. Thus, cimetidine administered 2 hours before a dose of azithromycin had no apparent effect on the serum concentrations of azithromycin.

Comparison of azithromycin and clarithromycin in their interactions with rifabutin in healthy volunteers.

A 14-day, randomized, open, phase I clinical trial was designed to examine possible pharmacokinetic interactions between rifabutin and two other antibiotics, azithromycin and clarithromycin, used in the treatment of Mycobacterium avium complex infections. Thirty healthy male and female volunteers were divided into five groups of six participants each: 18 received 300 mg/day of rifabutin, 12 in combination with therapeutic doses of either azithromycin or clarithromycin; the remaining 12 received azithromycin or clarithromycin alone. On day 10 the study was terminated because of adverse events, including severe neutropenia. Fourteen participants who received rifabutin developed neutropenia, including all 12 participants who received azithromycin or clarithromycin concomitantly. Analyses of serum revealed no apparent pharmacokinetic interaction between azithromycin and rifabutin. However, the mean concentrations of rifabutin and 25-O-desacetyl-rifabutin (an active metabolite) in participants who received clarithromycin and rifabutin concomitantly were more than 400% and 3,700%, respectively, of concentrations in those who received rifabutin alone. Physicians should be aware that recommended prophylactic doses of rifabutin may be associated with severe neutropenia within 2 weeks after initiation of therapy, and all patients receiving rifabutin, especially with clarithromycin, should be monitored carefully for neutropenia.

The effect of azithromycin on the pharmacokinetics of indinavir.

This study was performed to examine the effect of the coadministration of azithromycin on the pharmacokinetics of the protease inhibitor indinavir (Crixivan). In an open-label, parallel-design study, 32 healthy male and female volunteers were given indinavir (800 mg tid) for 5 days. One hour prior to the first dose of indinavir on day 5, 18 subjects received 1200 mg azithromycin (Zithromax), and 14 subjects received matching placebo. Serial samples of plasma were obtained for 8 hours following the morning dose of indinavir on days 4 and 5 and assayed for indinavir by HPLC/UV. Twenty-seven subjects completed the study. Following coadministration of azithromycin with indinavir, there was no significant change between day 5 and day 4 in AUC (20.7 mg.hr/ml and 23.1 mg.hr/ml; 90% CI on the ratio 81%-100%) or Cmax (9.88 mg/ml and 10.3 mg/ml; 90% CI 86%-108%). The day 5 to day 4 difference in indinavir concentrations following coadministration with azithromycin was not significantly different from the day 5 to day 4 difference with placebo (AUC p = 0.68; Cmax p = 0.074). Therefore, azithromycin does not significantly alter the kinetics of indinavir.

Fluconazole penetration into cerebrospinal fluid in humans.

One hour after intravenous doses of 50 mg/d fluconazole for 6 days or 100 mg/d for seven days to healthy subjects, the cerebrospinal fluid concentrations of fluconazole were 1.26 mg/L and 2.74 mg/L, respectively. These values were approximately 52% and 62% those of serum. Four patients with an initial clinical diagnosis of meningitis also had significant concentrations of fluconazole in the cerebrospinal fluid.

Pharmacokinetics of azithromycin after single- and multiple-doses in children.

STUDY OBJECTIVE: To characterize the disposition and tolerance of azithromycin after single and multiple oral doses of 12 mg/kg in children with and without cancer. DESIGN: Open-label, nonrandomized pharmacokinetic study. SETTING: Two pediatric hospitals. PATIENTS: Twelve children with cancer admitted to the inpatient unit for empiric antibiotic treatment of febrile neutropenia, and 16 hospitalized patients receiving antibiotic therapy INTERVENTIONS: Patients received azithromycin suspension either as a single dose or daily dose every morning for 5 consecutive days. Serial blood samples were collected up to 120 hours after a single dose or during and after multiple doses to characterize the pharmacokinetic parameters estimated for a two-compartment absorption model. MEASUREMENTS AND MAIN RESULTS: All 28 patients were evaluable for safety. Azithromycin was well tolerated except in one patient with cancer who experienced abdominal cramps and withdrew from the study. Pharmacokinetic results were not determined in five patients because of insufficient concentration-time data. The mean +/- SD estimates of oral clearance, terminal half-life, maximum concentration in serum (Cmax), and time to achieve Cmax in the 23 evaluable patients were 4.83 +/- 3.59 L/hour/kg, 54.5 +/- 36.4 hours, 318.2 +/- 174.5 microg/L, and 2.4 +/- 1.1 hours, respectively. These estimates did not differ between single-dose (14 patients) and multiple-dose (9 patients) groups. Pharmacokinetic parameters were not different between the 11 children with cancer and the 12 without cancer. CONCLUSION: Azithromycin 12 mg/kg results in proportionately higher serum concentrations than previously published results for lower doses (5 mg/kg). Variability in concentration profiles among patients is substantial, and age or other yet unidentified clinical factors may explain some of the differences observed.

DNA-binding affinities of MyoD and E47 homo- and hetero-dimers by capillary electrophoresis mobility shift assay.

A simple capillary electrophoresis mobility shift assay (CEMSA), with no gel and uncoated capillaries, for the accurate determination of protein-DNA affinities free in solution was applied to constructs of the MyoD/E47 DNA-binding proteins. The determined affinities are compared to those obtained by EMSA. MyoD-E47 covalent heterodimer binds DNA more tightly (Kd=1.8 nM) than MyoD (Kd=14.2 nM) or E47 (Kd= 11.5 nM) covalent homodimers. The effect of non-specific DNA on binding affinities was more important than salt concentration in the MyoD/E47 series. Application of this method to the MyoD/E47 system demonstrates the generality of our CEMSA.

Pharmacokinetic studies in animals of a new parenteral penem CP-65,207 and its oral prodrug ester.

The pharmacokinetics of penem CP-65,207 diastereomeric mixture were studied following parenteral administration in mice, rats, beagle dogs and cynomolgus monkeys. As is characteristic for most penems, the serum elimination T1/2 of CP-65,207 in rodents was only 13 minutes for mice and 18 minutes for rats. A linear relationship was observed between dose and Cmax following subcutaneous injection of drug in mice. The T1/2 in the beagle dog and monkey following intravenous injection was approximately 23 minutes. CP-65,207 demonstrated binding to human serum proteins of only 10%. In vitro studies using purified porcine renal dehydropeptidase-I (RDHP) indicated that the pure S-isomer of CP-65,207 was 7-fold more stable to inactivation than imipenem. Urinary recovery of CP-65,207 in the dog was 42% compared to 1% for imipenem without RDHP inhibitor. Unlike results obtained with imipenem, coadministration of probenecid with CP-65,207 in the dog doubled the elimination T1/2 and AUC of the penem demonstrating its relative stability in vivo in the absence of a RDHP inhibitor. The pivaloyloxymethyl esters of each pure isomer of CP-65,207 showed significantly different degrees of oral absorption in rats.

The parenteral kinetics of ampicillin/sulbactam in man.

The kinetics of co-administered ampicillin plus sulbactam were examined at doses being used in clinical trials of this combination of a beta-lactam antibiotic (ampicillin) and a beta-lactamase inhibitor (sulbactam). Following 15-min infusion of 2 g ampicillin plus 1 g sulbactam, peak serum concentrations of 120 micrograms/ml ampicillin and 60 micrograms/ml sulbactam were observed. The half-life was approximately one hour for both drugs. Approximately 75% of the dose of sulbactam and ampicillin was recovered in urine. The data fit a two-compartment pharmacokinetic model. Intramuscular administration of 1 g ampicillin plus 0.5 g sulbactam produced mean peak concentrations of 18 micrograms/ml ampicillin plus 13 micrograms/ml sulbactam. Estimates of variability of the data in normal male subjects are provided to serve as references for clinical trials.

Pharmacokinetic study of azithromycin with fluconazole and cotrimoxazole (trimethoprim-sulfamethoxazole) in healthy volunteers.

BACKGROUND: Azithromycin, fluconazole and cotrimoxazole (trimethoprim-sulfamethoxazole; TMP/SMX) are all agents that are utilised for the treatment and/or prophylaxis of opportunistic infections in patients with AIDS. OBJECTIVE: To characterise the potential for an interaction when azithromycin is coadministered with cotrimoxazole or with fluconazole. DESIGN: Two separate nonblind randomised studies were conducted in healthy volunteers. During the fluconazole study the potential for fluconazole to adversely affect the pharmacokinetics of azithromycin was also studied. PARTICIPANTS: 24 (cotrimoxazole) and 18 (fluconazole) healthy male and female volunteers. RESULTS: The results of both studies indicated that neither the peak concentrations of nor the exposures (area under the concentration-time curve) to the test drugs were changed when azithromycin was coadministered. In addition, fluconazole did not significantly alter the pharmacokinetic parameters of azithromycin. CONCLUSIONS: Azithromycin does not alter the bioavailability of either cotrimoxazole or fluconazole.

Pharmacokinetics of sulbactam/ampicillin in humans: a review.

The parenteral kinetics of sulbactam, a potent synergist with ampicillin against a broad range of clinically important organisms in humans, are similar to those of ampicillin. The kinetics of ampicillin were not affected by co-administration of sulbactam, and high levels of both agents were attained: 15-min infusions of 2 g of ampicillin plus 1 g of sulbactam produced peak serum concentrations of approximately 120 micrograms of ampicillin/ml plus 60 micrograms of sulbactam/ml; intramuscular injections of 1 g of ampicillin plus 0.5 g of sulbactam produced peak concentrations of 18 micrograms of ampicillin/ml plus 13 micrograms of sulbactam/ml. The drugs had similar half-lives (approximately 1 hr), and both drugs were excreted primarily in the urine (greater than 75%). Although the kinetics of sulbactam in postpartem women and in surgical patients were similar to the kinetics in young men, the half-life of sulbactam (like that of ampicillin) was altered in the elderly, during labor, in neonates, and in patients with renal impairment. After distribution of the agents in the body, the concentrations of both drugs in blister and parenteral fluid were similar to those in serum. Furthermore, useful antibacterial concentrations of both drugs were found in pus, sputum, and middle-ear fluid. The normally low penetration of sulbactam and ampicillin into cerebrospinal fluid was increased in patients with bacterial meningitis.