Doxycycline in serum and bronchial secretions

Oral antibiotics used in the treatment of chronic rhinosinusitis have limited penetration into the sinonasal mucosa: a randomized trial

Despite the widespread prescription of antibiotics for patients with chronic rhinosinusitis (CRS), the extent to which drug distribution to the sinonasal mucosa occurs remains largely undefined. Twenty subjects undergoing functional endoscopic sinus surgery (FESS) for CRS were randomized to one of two groups: 1) doxycycline (100 mg daily for seven days) 2) roxithromycin (300 mg daily for seven days). Drug levels were measured using liquid chromatography-tandem mass spectrometry in sinonasal mucus, sinonasal tissues and serum at steady state. Doxycycline concentrations measured in the mucus were significantly lower compared to that in the serum (mean mucus/serum ratio = 0.16, p < 0.001) and the tissue (mean mucus/tissue ratio = 0.18, p < 0.0001). Roxithromycin concentrations in the mucus were also significantly lower compared to that in the serum (mean mucus/serum ratio = 0.37, p = 0.002) and the tissue (mean mucus/tissue ratio = 0.60, p < 0.001). Although the efficacy of doxycycline and roxithromycin in sinonasal mucus in vivo cannot be predicted solely from reported minimum inhibitory concentrations, given the added complexity of bacterial biofilm antimicrobial tolerance, these results suggest that low mucosal penetration of antibiotics may be one of the factors contributing to the limited efficacy of these agents in the treatment of CRS.

A Tet-Off gene expression system for validation of antifungal drug targets in a murine invasive pulmonary aspergillosis model

Aspergillus fumigatus is one of the major causes of invasive pulmonary aspergillosis in immunocompromised patients. Novel antifungal therapy is in urgent need due to emerging resistance and adverse toxicity of current antifungal drugs. Gene products that are essential for Aspergillus viability during infection are attractive drug targets. To characterize these genes in vivo we developed a Tet-Off gene expression system in A. fumigatus, whereby the administration of doxycycline resulted in down regulation of the gene whose expression is under the control of the Tet-Off promoter. We tested the system on two potential drug targets, inosine 5′-monophosphate dehydrogenase (IMPDH) and L-ornithine N⁵-oxygenase (sidA) in a murine invasive pulmonary aspergillosis model. We show that depletion of IMPDH attenuated but did not completely abolish virulence in vivo whereas turning off the expression of sidA, which is required for iron acquisition, resulted in avirulence. We also investigated whether sidA expression could be controlled in a time-dependent manner in mice. Our results demonstrated that timing of doxycycline administration dramatically affects survival rate, suggesting that this genetic system can be used for testing whether an antifungal drug target is critical for fungal growth post-infection.

Doxycycline suppresses Chlamydia pneumoniae-mediated increases in ongoing immunoglobulin E and interleukin-4 responses by peripheral blood mononuclear cells of patients with allergic asthma

OBJECTIVES

Chlamydia pneumoniae, an obligate intracellular bacterium, has been associated with asthma and the induction of immunoglobulin E (IgE) responses. Whereas tetracyclines have anti-chlamydial activity, their effect on human IgE responses to C. pneumoniae has not been studied.

METHODS

Peripheral blood mononuclear cells (PBMCs) from serum IgE+ allergic asthmatic subjects (n = 11) and healthy controls (n = 12) were infected with C. pneumoniae and cultured for 12 days with or without doxycycline (0.01-1.0 mg/L). IgE, interferon (IFN)-γ and interleukin (IL)-4 levels in supernatants were determined on days 1-12 post-infection, and C. pneumoniae DNA copy numbers in PBMC culture were measured on day 2 (quantitative PCR).

RESULTS

C. pneumoniae-infected PBMCs from allergic asthmatic individuals had increased levels of IgE in supernatants compared with uninfected PBMCs (520% on day 10 post-infection, P = 0.008). IgE levels in PBMC cultures from controls were undetectable (<0.3 ng/mL). Increases in C. pneumoniae-induced IgE in asthmatics correlated with those of C. pneumoniae-induced IL-4 (r = 0.98; P < 0.001), but not with IFN-γ. The addition of doxycycline (1.0 mg/L) to the culture strongly suppressed the production of IgE (>70%, P = 0.04) and IL-4 (75%, P = 0.018), but not IFN-γ. The suppressive effect on IL-4 production remained significant even at concentrations of doxycycline that were subinhibitory (0.01 mg/L) for C. pneumoniae. In both asthmatic participants and controls, no significant effect of doxycycline on DNA copy numbers of C. pneumoniae was observed.

CONCLUSIONS

Doxycycline suppressed the C. pneumoniae-induced production of IgE and IL-4, but not IFN-γ, in PBMCs from IgE+ allergic asthmatic subjects. These findings resulted from the immunomodulatory anti-allergic properties of tetracyclines.

Pharmacokinetics of doxycycline in adults with cystic fibrosis

Cystic fibrosis (CF) is characterized by a chronic neutrophilic inflammatory response resulting in airway remodeling and progressive loss of lung function. Doxycycline is a tetracycline antibiotic that inhibits matrix metalloproteinase 9, a protease known to be associated with the severity of lung disease in CF. The pharmacokinetics of doxycycline was investigated during the course of a clinical trial to evaluate the short-term efficacy and safety in adults with CF. Plasma samples were obtained from 14 patients following a single intravenous dose and after 2 and 4 weeks of oral administration of doses ranging from 40 to 200 mg daily. The data were analyzed using noncompartmental and compartmental pharmacokinetics. The maximum concentration of drug in serum (C(max)) and area under the concentration-time curve from 0 h to infinity (AUC(0-∞)) values ranged from 1.0 to 3.16 mg/liter and 15.2 to 47.8 mg/liter × h, respectively, following single intravenous doses of 40 to 200 mg. C(max) and time to maximum concentration of drug in serum (T(max)) values following multiple-dose oral administration ranged from 1.15 to 3.04 mg/liter and 1.50 to 2.33 h, respectively, on day 14 and 1.48 to 3.57 mg/liter and 1.00 to 2.17 on day 28. Predose sputum/plasma concentration ratios on days 14 and 28 ranged from 0.33 to 1.1 (mean, 0.71 ± 0.33), indicating moderate pulmonary penetration. A 2-compartment model best described the combined intravenous and oral data. Absorption was slow and delayed (absorption rate constant [K(a)], 0.414 h(-1); lag time, 0.484 h) but complete (bioavailability [F], 1.16). The distribution and elimination half-lives were 0.557 and 18.1 h, respectively. Based on these data, the plasma concentrations at the highest dose, 200 mg/day, are in the range reported to produce anti-inflammatory effects in vivo and should be evaluated in clinical trials.

Pharmacokinetics of oral doxycycline and concentrations in body fluids and bronchoalveolar cells of foals

The objective of this study was to determine the disposition of orally administered doxycycline in foals. Six healthy 4- to 8-week-old foals were used. Doxycycline was administered to each foal via the intragastric (IG) route at dosages of 10 and 20 mg/kg, in a cross-over design. After the first 10 mg/kg dose, five additional doses were administered at 12-h intervals. A microbiological assay was used to measure doxycycline activity in serum, urine, peritoneal fluid, synovial fluid, cerebrospinal (CSF), pulmonary epithelial lining fluid (PELF), and bronchoalveolar (BAL) cells. Following administration at 10 mg/kg, mean+/-SD time to peak serum doxycycline activity (tmax) was 3.0+/-1.2 h, maximum serum activity (Cmax) was 2.54+/-0.27 microg/mL, and terminal half-life (t1/2) was 8.5+/-2.8 h. Administration at a dose of 20 mg/kg resulted in a significantly longer tmax (5.5+/-1.8 h) as well as a tendency toward higher Cmax (2.89+/-0.33 microg/mL) and longer t1/2 (11.9+/-2.6 h). After multiple IG doses, doxycycline activity in CSF was significantly lower than concurrent serum activity, whereas peritoneal fluid, synovial fluid, and BAL cell doxycycline activity was similar to concurrent serum activity. Doxycycline activity in urine and PELF was significantly higher than that found at other sites. Oral administration at a dosage of 10 mg/kg every 12 h would maintain serum, PELF, and BAL cell activity above the minimum inhibitory concentrations of Rhodococcus equi, beta-hemolytic streptococci, and other susceptible bacterial pathogens for the entire dosing interval.

Doxycycline decreases monocyte chemoattractant protein-1 in human lung epithelial cells

Certain antibiotics possess anti-inflammatory properties and could potentially be used to treat inflammatory lung diseases associated with an influx of monocytes such as panbronchiolitis, asthma, cystic fibrosis, and bronchitis. Doxycycline is reported to possess anti-inflammatory effects. Monocyte chemoattractant protein-1 (MCP-1) is a major inflammatory cytokine and a powerful chemoattractant for monocytes. The authors hypothesized that doxycycline exerts its anti-inflammatory effects, in part, by reducing MCP-1 production. To test this hypothesis, A549 human lung epithelial cells were stimulated with cytomix in the presence or absence of doxycycline. In stimulated cells doxycycline decreased MCP-1 production by 95% and in monocyte chemotaxis assays migration decreased by 55%. However, doxycycline did decrease expression of MCP-1 mRNA and did not effect its stability. These data demonstrate that doxycycline modulates MCP-1 production and suggest that doxycycline may provide a new anti-inflammatory therapy for chronic lung diseases.

Doxycycline modulates nitric oxide production in murine lung epithelial cells

Many effective therapeutic agents exhibit effects that are different from their intended primary mode of action. Antibiotics such as doxycycline and erythromycin A are no exception. They also display anti-inflammatory activity. Using LA4 murine lung alveolar epithelial cells, effects of doxycycline and erythromycin A on inducible NO synthase (iNOS) NO production as well as iNOS protein and mRNA production were investigated. Induction of iNOS was accomplished by treatment with cytomix (TNF-alpha, IL-1beta, and IFN-gamma each at 5 ng/ml). Production of NO or iNOS was not detected in controls with or without erythromycin A. In the presence of cytomix, erythromycin A did not decrease NO, nitrite, iNOS protein, or mRNA production. In contrast, doxycycline caused a dose-dependent decrease in NO, nitrite, iNOS protein, and mRNA production in cytomix-treated cells. Doxycycline at 30 mug/ml produced a 90% decrease in nitrite and NO production and a 52% decrease in iNOS mRNA transcription compared with cytomix treatment alone. Actinomycin D treatment suggests that doxycycline decreases stability of iNOS mRNA in cytomix-treated cells. To determine a mechanism for the decrease in iNOS expression, NF-kappaB and AP-1 transcription regulatory systems and p38 MAPK were examined. Doxycycline treatment gave no statistically significant change in NF-kappaB activation but did decrease p38 MAPK protein in cytomix-treated cells by 50%, suggesting that p38 MAPK may be responsible for stabilization of iNOS mRNA. These results demonstrate that doxycycline decreases NO production from iNOS by destabilization of iNOS mRNA via decreased expression of p38 MAPK.

Pharmacokinetics of antimicrobial agents in the respiratory tract

The ability of antibiotics to penetrate into the respiratory tract has been investigated at several sites, namely, sputum and bronchial secretions, tissue homogenates, pleural fluid and, more recently, epithelial lining fluid and alveolar macrophages. The major reason for such investigations is that these data may be helpful to a more thorough understanding of drug distribution in the lung tissue and fluids and to a more accurate prediction of clinical outcome. However, the study of drug concentration at each of these sites presents problems in terms of methodology and data interpretation. The advantages and disadvantages of each of these methods are considered, and the data on penetration of betalactams, aminoglycosides, macrolides, fluoroquinolones and other antimicrobial agents (including antifungal and antiprotozoan drugs) are reviewed.

Pharmacokinetics and tissue localization of doxycycline polyphosphate and doxycycline hydrochloride in the rat

Two doxycycline derivatives Doxycycline polyphosphate and Doxycycline hydrochloride were administered to rats at a dose of 20 mg/kg body weight. Doxycycline tissue levels were determined using a microbiological assay. Only an insignificant fraction of the antibiotics was found to cross the blood brain barrier. Doxycycline was highly concentrated in excretory organs: liver, kidneys and caecum. The high intestinal drug level observed is probably related to the entero-hepatic cycle of this antibiotic. There was a good correlation between serum and heart doxycycline concentration; heart level was about twice that of serum. In lung, antibiotic level was always higher than in serum.

Penetration of piperacillin into bronchial mucosa and sputum

Bronchial mucosal biopsies were obtained during fibreoptic bronchoscopy in 12 patients receiving a new semisynthetic penicillin, piperacillin. The piperacillin levels estimated in bronchial mucosa exceeded those required to eradicate organisms associated with acute bronchitis, Haemophilus influenzae and Streptococcus pneumoniae, and compared favourably with those required for activity against a wide variety of anaerobic and Gram-negative organisms including Pseudomonas aeruginosa. Sputum and serum piperacillin levels were obtained from eight patients with bronchial disease receiving a five to seven day course (8 to 16 g/day). Sputum/serum level ratios were constant for the two dosages (10.7% for 8 g/day; 14.3% for 16 g/day) suggesting a diffusion transfer process, although the presence of pus in the sputum appeared to facilitate penetration. Seven patients achieved sputum levels exceeding those required for activity against Haemophilus influenzae and Streptococcus influenzae, and four for Pseudomonas aeruginosa. This study provides pharmacolinetic support of the use of piperacillin in bronchopulmonary infection.

Serum, saliva, and sputum levels of metronidazole in acute exacerbations of chronic bronchitis

We have evaluated the absorption and the penetration of metronidazole into the bronchial secretions and saliva in acute infective exacerbations of chronic bronchitis. Seventeen patients were given 400 mg orally three times daily for seven days and "steady state" levels were measured in serum, saliva, and sputum on the last day of treatment. Mean levels in the three biological fluids were not significantly different. Higher metronidazole levels in sputum tended to occur in patients with higher serum levels. In all but one patient, levels in serum and saliva were well within the therapeutic range. We conclude that this oral regimen results in therapeutic tissue levels in acute exacerbations of chronic bronchitis.

Tissue levels of doxycycline in the human lung and pleura

Antibiotic concentrations in the human lung and pleural tissue were measured following intravenous administration of doxycycline. The average serum levels were 9.3, 7.0 and 3.0 micrograms/ml at 1, 2, and 3 hours; correspondingly, the lung tissue levels were 6.8, 3.5 and 2.3 micrograms/g. The pleural tissue antibiotic concentrations at the same time intervals were 2.5, 1.5, and 1.5 micrograms/g. This suggests that doxycycline is retained well by the lung and the pleura, well above the minimal inhibitory concentration of most of the common bacterial pathogens of the lung, and may be used in the treatment of lung infections caused by susceptible organisms.

Plasma and sputum erythromycin concentrations in chronic bronchitis

Plasma and sputum concentrations of erythromycin were measured in 10 patients with chronic bronchitis during an eight-day course of a new formulation of erythromycin stearate. The plasma erythromycin levels compared favourably with the minimal inhibitory concentrations for common respiratory pathogens and indicated adequate gastrointestinal absorption when the drug was taken immediately before food. Sputum erythromycin levels were variable and in some patients low or undetectable. Measurable sputum erythromycin levels were approximately 10% of plasma levels with no evidence of accumulation and were of similar order of magnitude to the minimal inhibitory concentrations for common respiratory pathogens except Haemophilus influenzae. There was no correlation between sputum and plasma erythromycin levels. There was a trend for higher erythromycin levels in sputum containing increasing amounts of pus and also when plasma levels increased.

Malingering: a dangerous diagnosis

Karl Kast, a migrant with a bad back, was examined by four Brisbane orthopaedic surgeons who all independently agreed that there was no physical basis for his complaint. After brooding over this for months, he resolved to kill these doctors and shot three (killing two) before taking his own life. This tragedy and its background are summarized, and a second instance is recorded where a surgeon could have been killed by another accident litigant. There is more to emotional disturbance after injury than a mere quest for compensation. Doctors who hold this simple belief may be at risk if they do not carefully handle the rare cases of severe and dangerous mental illness which masquerade as malingering.