The effect of respiratory disorders on clinical pharmacokinetic variables

Optimizing tylosin dosage for co-infection of Actinobacillus pleuropneumoniae and Pasteurella multocida in pigs using pharmacokinetic/pharmacodynamic modeling

Formulating a therapeutic strategy that can effectively combat concurrent infections of Actinobacillus pleuropneumoniae (A. pleuropneumoniae) and Pasteurella multocida (P. multocida) can be challenging. This study aimed to 1) establish minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), time kill curve, and post-antibiotic effect (PAE) of tylosin against A. pleuropneumoniae and P. multocida pig isolates and employ the MIC data for the development of epidemiological cutoff (ECOFF) values; 2) estimate the pharmacokinetics (PKs) of tylosin following its intramuscular (IM) administration (20 mg/kg) in healthy and infected pigs; and 3) establish a PK-pharmacodynamic (PD) integrated model and predict optimal dosing regimens and PK/PD cutoff values for tylosin in healthy and infected pigs. The MIC of tylosin against both 89 and 363 isolates of A. pleuropneumoniae and P. multocida strains spread widely, ranging from 1 to 256 μg/mL and from 0.5 to 128 μg/mL, respectively. According to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) ECOFFinder analysis ECOFF value (≤64 µg/mL), 97.75% (87 strains) of the A. pleuropnumoniae isolates were wild-type, whereas with the same ECOFF value (≤64 µg/mL), 99.72% (363 strains) of the P. multicoda isolates were considered wild-type to tylosin. Area under the concentration time curve (AUC), T1/2, and Cmax values were significantly greater in healthy pigs than those in infected pigs (13.33 h × μg/mL, 1.99 h, and 5.79 μg/mL vs. 10.46 h × μg/mL, 1.83 h, and 3.59 μg/mL, respectively) (p < 0.05). In healthy pigs, AUC24 h/MIC values for the bacteriostatic activity were 0.98 and 1.10 h; for the bactericidal activity, AUC24 h/MIC values were 1.97 and 1.99 h for A. pleuropneumoniae and P. multocida, respectively. In infected pigs, AUC24 h/MIC values for the bacteriostatic activity were 1.03 and 1.12 h; for bactericidal activity, AUC24 h/MIC values were 2.54 and 2.36 h for A. pleuropneumoniae and P. multocida, respectively. Monte Carlo simulation lead to a 2 μg/mL calculated PK/PD cutoff. Managing co-infections can present challenges, as it often demands the administration of multiple antibiotics to address diverse pathogens. However, using tylosin, which effectively targets both A. pleuropneumoniae and P. multocida in pigs, may enhance the control of bacterial burden. By employing an optimized dosage of 11.94-15.37 mg/kg and 25.17-27.79 mg/kg of tylosin can result in achieving bacteriostatic and bactericidal effects in 90% of co-infected pigs.

Tigecycline Pharmacokinetic and Pharmacodynamic Profile in Patients with Chronic Obstructive Pulmonary Disease Exacerbation

BACKGROUND

We aimed to evaluate the pharmacokinetic profile of tigecycline in plasma and its penetration to sputum in moderately ill patients with an infectious acute exacerbation of chronic obstructive pulmonary disease (COPD).

METHODS

Eleven patients hospitalized with acute respiratory failure due to an acute COPD exacerbation with clinical evidence of an infectious cause received tigecycline 50 mg twice daily after an initial loading dose of 100 mg. Blood and sputum samples were collected at steady state after dose seven.

RESULTS

In plasma, mean C_max pl was 975.95 ± 490.36 ng/mL and mean C_min pl was 214.48 ±140.62 ng/mL. In sputum, mean C_{max sp} was 641.91 ± 253.07 ng/mL and mean C_{min sp} was 308.06 ± 61.7 ng/mL. In plasma, mean AUC _{0-12 pl} was 3765.89 ± 1862.23 ng*h/mL, while in sputum mean AUC _{0-12 sp} was 4023.27 ± 793.37 ng*h/mL. The mean penetration ratio for the 10/11 patients was 1.65 ± 1.35. The mean Free AUC_{0-24 pl}/MIC ratio for Streptococcus pneumoniae and Haemophilus influenzae was 25.10 ± 12.42 and 6.02 ± 2.97, respectively.

CONCLUSIONS

Our findings support the clinical effectiveness of tigecycline against commonly causative bacteria in COPD exacerbations and highlight its sufficient lung penetration in pulmonary infections of moderate severity.

Drug metabolism in severe chronic obstructive pulmonary disease: A phenotyping cocktail study

AIMS

To evaluate the effect of severe chronic obstructive pulmonary disease (COPD) on drug metabolism by comparing the pharmacokinetics of patients with severe COPD with healthy volunteers and using the modified Inje drug cocktail.

METHODS

This was a single-centre pharmacokinetic study with 12 healthy participants and 7 participants with GOLD D COPD. Midazolam 1 mg, dextromethorphan 30 mg, losartan 25 mg, omeprazole 20 mg, caffeine 130 mg and paracetamol 1000 mg were simultaneously administered and intensive pharmacokinetic sampling was conducted over 8 hours. Drug metabolism by CYP3A4, CYP2D6, CYP2C9, CYP2C19, CYP1A2, UGT1A6 and UGT1A9 in participants with COPD were compared with phenotypes in healthy controls.

RESULTS

The oral clearance (95% confidence interval) in participants with COPD relative to controls was: midazolam 63% (60-67%); dextromethorphan 72% (40-103%); losartan 53% (52-55%); omeprazole 35% (31-39%); caffeine 52% (50-53%); and paracetamol 73% (72-74%). There was a 5-fold increase in AUC for omeprazole and approximately 2-fold increases for caffeine, losartan, dextromethorphan, and midazolam. The AUC of paracetamol, which is mostly glucuronidated, was increased by about 60%.

CONCLUSION

Severe COPD is associated with a clinically significant reduction in oral drug clearance. This may be greater for cytochrome P450 substrates than for glucuronidated drugs. This supports reduced starting doses when prescribing for patients with severe COPD.

A review of the pharmacokinetics of M3 muscarinic receptor antagonists used for the treatment of asthma

Introduction: There is solid evidence that in patients with poorly controlled severe asthma despite the use of ICS and LABA, the addition of LAMAs, such as tiotropium, significantly increases the time to the first severe exacerbation and provides a modest but sustained bronchodilation. However, only a very limited number of pharmacokinetic studies with these agents have been performed in asthmatic patients.Areas covered: The pharmacokinetic profile of inhaled tiotropium, umeclidinium and glycopyrronium in healthy volunteers and that of inhaled tiotropium and umeclidinium in asthmatic patients have been reviewed.Expert opinion: In asthmatic patients, LAMAs are rapidly absorbed into the systemic compartment and demonstrate bi-exponential elimination (rapidly declining plasma concentrations followed by slow apparent terminal elimination). Apparently, the severity of asthma does not change the pharmacokinetics of LAMAs. The limited information available is focused on the plasma pharmacokinetic profile of these drugs and, consequently, although suitable for establishing a systemic safety profile, it does not tell us much about possible therapeutic efficacy of LAMAs in asthmatics because quantification of systemic plasma values is neither at the airways, which are their site of action nor representative of their transport to this site.

The effects of Mannheimia haemolytica and albendazole on marbofloxacin pharmacokinetics in lambs

The study aimed to define the effects of M. haemolytica and a single oral dose of albendazole on the single-dose pharmacokinetics of marbofloxacin in lambs. The pharmacokinetic-pharmacodynamic integration of marbofloxacin was applied to describe a 3 mg/kg intramuscular dose in lambs. The 6 healthy and 12 naturally infected with M. haemolytica lambs (Akkaraman, males weighing 10-15 kg and aged 2-3 months) were used in this study. In the marbofloxacin group, 6 healthy lambs received marbofloxacin. In the albendazole group after 2 weeks washout period, the same animals received marbofloxacin on 1 h after albendazole. In the diseased marbofloxacin group, 6 lambs naturally infected with M. haemolytica received marbofloxacin. In the diseased albendazole group, 6 lambs naturally infected with M. haemolytica received marbofloxacin on 1 h after albendazole. The marbofloxacin and albendazole were administered each as a single dose of 3 mg/kg intramuscular and 7.5 mg/kg oral, respectively, in the respective groups. Plasma concentration of marbofloxacin was measured with HPLC-UV and pharmacokinetic parameters were analyzed by non-compartmental model. Albendazole did not change the pharmacokinetic profiles of marbofloxacin in healthy and diseased lambs. However, M. haemolytica affected the pharmacokinetics of marbofloxacin in diseased lambs, AUC_0-24/MIC₉₀ ratio was not found to be higher than 125, but C_max/MIC₉₀ ratios was found to be higher than 10 for an MIC value of 0.25 μg/mL in all groups. The marbofloxacin dose described in this study may not be effective for the treatment of infections due to M. haemolytica in lambs, with MIC ≤ 0.25 μg/mL.

Clinical pharmacokinetics of drugs in cardiopulmonary associated cachexia without hepatorenal pathology: a systematic review

Cachexia not only has a dramatically harmful impact on a patient's life, but also a poor response to therapeutic agents. The purpose of the present review is to provide updated information concerning the pharmacokinetic aspects of drugs used to treat cardiopulmonary cachexia in patients with no signs of hepatic or renal pathology. A systematic search of PubMed, the Cochrane Central Register of Control Trials, Science Direct, and Clinical Trials Registry (ClinicalTrials.gov), encompassing the period between 2000 and 2017, was conducted in accordance to PRISMA guidelines. Seven studies were identified. Collectively, these studies included a total of 196 individuals (19 healthy subjects and 177 diseased patients). This data review found no differences in bisoprolol and prothionamide absorption in cachectic patients with chronic heart failure and tuberculosis, but higher absorption of oflaxocin in the same set of patients was observed. The distribution of bisoprolol, prothionmaide, ceftazidime, and cefipirome was reduced in cardiopulmonary cachexia patients. Hepatic clearance of rifampin was equivalent in cachectic and non-cachectic patients that had normal hepatic function. Similarly in cardiopulmonary cachexia patients, renal clearance of ceftazidime was reduced by 19% but no significant differences in bisorpolol and prothionamide clearance were observed. In the case of cefipirome, both renal clearance and creatinine clearance were higher in cachectic patients with cystic fibrosis. From the limited evidence available, the main drug pharmacokinetic changes seen in cardiopulmonary cachexia patients were a reduction in the volume of distribution and impairment of clearance.

Elevated suicide rates at high altitude: sociodemographic and health issues may be to blame

Suicide rates are higher at high altitudes; some hypothesize that hypoxia is the cause. We examined 8,871 suicides recorded in 2006 in 15 states by the National Violent Death Reporting System, with the victim's home county altitude determined from the National Elevation Dataset through FIPS code matching. We grouped cases by altitude (low<1000m; middle=1000-1999m; high≥2000m). Of reported suicides, 5% were at high and 83% at low altitude, but unadjusted suicide rates per 100,000 population were higher at high (17.7) than at low (5.7) altitude. High and low altitude victims differed with respect to race, ethnicity, rural residence, intoxication, depressed mood preceding the suicide, firearm use and recent financial, job, legal, or interpersonal problems. Even after multivariate adjustment, there were significant differences in personal, mental health, and suicide characteristics among altitude groups. Compared to low altitude victims, high altitude victims had higher odds of having family or friends report of a depressed mood preceding the suicide (OR 1.78; 95%CI:1.46-2.17) and having a crisis within 2weeks before death (OR 2.00; 95%CI:1.63-1.46). Suicide victims at high and low altitudes differ significantly by multiple demographic, psychiatric, and suicide characteristics; these factors, rather than hypoxia or altitude itself, may explain increased suicide rates at high altitude.

Hypoxia--implications for pharmaceutical developments

Cells sense oxygen availability using not only the absolute value for cellular oxygen in regard to its energetic and metabolic functions, but also the gradient from the cell surface to the lowest levels in the mitochondria. Signals are used for regulatory purposes locally as well as in the generation of cellular, tissue, and humoral remodeling. Lowered oxygen availability (hypoxia) is theoretically important in the consideration of pharmacology because (1) hypoxia can alter cellular function and thereby the therapeutic effectiveness of the agent, (2) therapeutic agents may potentiate or protect against hypoxia-induced pathology, (3) hypoxic conditions may potentiate or mitigate drug-induced toxicity, (4) hypoxia may alter drug metabolism and thereby therapeutic effectiveness, and (5) therapeutic agents might alter the relative coupling of blood flow and energy metabolism in an organ. The prototypic biochemical effect of hypoxia is related to its known role as a cofactor in a number of enzymatic reactions, e.g., oxidases and oxygenases, which are affected independently from the bioenergetic effect of low oxygen on energetic functions. The cytochrome P-450 family of enzymes is another example. Here, there is a direct effect of oxygen availability on the conformation of the enzyme, thereby altering the metabolism of drug substrates. Indirectly, the NADH/NAD+ ratio is increased with 10% inspired oxygen, leading not only to reduced oxidation of ethanol but also to reduction of azo- and nitro-compounds to amines and disulfides to sulfhydryls. With chronic hypoxia, many of these processes are reversed, suggesting that hypoxia induces the drug-metabolizing systems. Support for this comes from observations that hypoxia can induce the hypoxic inducible factors which in turn alters transcription and function of some but not all cytochrome P-450 isoforms. Hypoxia is identified as a cofactor in cancer expression and metastatic potential. Thus, the effects of hypoxia play an important role in pharmacology, and the signaling pathways that are affected by hypoxia could become new targets for novel therapy or avenues for prevention.

The effect of hypoxic hypoxia on the systemic and myocardial pharmacokinetics and dynamics of lidocaine in sheep

It was hypothesized that the increased myocardial blood flow known to occur during some types of hypoxia may alter the kinetics and dynamics of cardio-active drugs such as lidocaine that act directly on the myocardium. In a randomized cross-over design, iv lidocaine (100 mg over 2 min) was administered to conscious instrumented sheep in a control state (C) or when the sheep were rendered hypoxic (H) by the addition of nitrogen to their inspired air (average Pa(O2) = 26 mmHg). Hypoxia caused a significant increase in myocardial blood flow (193% of control, SD = 37%, p < 0.05), a nonsignificant increase in cardiac output, and unchanged heart rate and blood pressure. Peak arterial lidocaine concentrations were unchanged, but peak concentrations in coronary sinus blood (effluent from the myocardium) were increased (maximum 201% of control, SD = 63%, p < or = 0.05), suggesting more rapid uptake of lidocaine into the myocardium in hypoxia. There was a linear relationship between coronary sinus lidocaine concentrations and reductions in myocardial contractility. However, the higher myocardial concentrations associated with H were not associated with overall greater reductions in contractility, as baseline contractility was elevated by H. Thus, hypoxia was not detrimental with respect to this adverse effect of lidocaine on the myocardium.

Differential effects of various antiinflammatory drugs on theophylline neurotoxicity

The purpose of the present investigation was to evaluate whether antiinflammatory drugs affect the pharmacodynamics of theophylline-induced seizures. Adult male Lewis rats were treated with either dexamethasone (DEX), hydrocortisone (HYD), ibuprofen (IBU), or mefenamic acid (MFA), for 4 consecutive days. On the fourth day they received a constant infusion of theophylline (2 mg/min IV) until the onset of maximal seizures. Then, blood and cerebrospinal fluid (CSF) were obtained for theophylline concentration determinations by HPLC. It was found that pretreatment with the corticosteroids DEX and HYD elevated the CSF theophylline concentration required to induce maximal seizures in comparison to the untreated rats (242 +/- 6, 232 +/- 6, and 203 +/- 10 mg/l, respectively, n = 10, p < 0.05). MFA also increased the CSF theophylline concentration at that end-point in comparison to the controls (p < 0.01), whereas pretreatment with IBU had no effect (280 +/- 10 MFA, 225 +/- 9 IBU vs. 220 +/- 8 controls, n = 12). The data suggests that concomitant treatment with antiinflammatory drugs, together with theophylline, do not increase the risk for theophylline-induced seizures. Moreover, in certain cases they may elevate the seizure threshold and protect against these hazardous episodes.

Clinical pharmacokinetics of theophylline during co-treatment with ticarcillin plus clavulanic acid in patients suffering from acute exacerbation of chronic bronchitis

The effect of ticarcillin/clavulanic acid, taken for 7 days as vials containing 1000 mg of ticarcillin and 200 mg of clavulanic acid twice daily intramuscularly, on the steady-state pharmacokinetics of theophylline was studied in 12 patients suffering from acute exacerbation of chronic obstructive pulmonary disease. Initially, patients were treated for four days with theophylline as sustained-release formulation in the amount of 600 mg daily; on the last day, blood samples were taken for theophylline determination. Theophylline concentrations were measured serially for 12 hours by the method of polarized immunofluorescence (Abbott TDx system). Subsequently, while theophylline was continued at the same dosage, each patient received in addition ticarcillin/clavulanic acid vials every 12 hours. After seven days of this combined medication, the serial assays of plasma were repeated at the same time intervals as before. No influence of ticarcillin/clavulanic acid was detectable on the steady-state theophylline pharmacokinetics. It is concluded that both drugs can be administered concomitantly without any dosage adjustment of theophylline.