Comparative study of bioavailabilities and pharmacokinetics of clindamycin in healthy volunteers and patients with AIDS

Interaction of ceftazidime and clindamycin with extracorporeal life support

BACKGROUND

Ceftazidime and clindamycin are commonly prescribed to critically ill patients who require extracorporeal life support such as ECMO and CRRT. The effect of ECMO and CRRT on the disposition of ceftazidime and clindamycin is currently unknown.

METHODS

Ceftazidime and clindamycin extraction were studied with ex vivo ECMO and CRRT circuits primed with human blood. The percent recovery of these drugs over time was calculated to determine the degree of interaction between these drugs and circuit components.

RESULTS

Neither ceftazidime nor clindamycin exhibited measurable interactions with the ECMO circuit. In contrast, CRRT cleared 100% of ceftazidime from the experimental circuit within the first 2 h. Clearance of clindamycin from the CRRT circuit was slower, with about 20% removed after 6 h.

CONCLUSION

Clindamycin and ceftazidime dosing adjustments are likely required in patients who are supported with CRRT, and future studies to quantify these adjustments should consider the pathophysiology of the patient in combination with the clearance due to CRRT. Dosing adjustments to account for adsorption to ECMO circuit components are likely unnecessary and should focus instead on the pathophysiology of the patient and changes in volume of distribution. These results will help improve the safety and efficacy of ceftazidime and clindamycin in patients requiring ECMO and CRRT.

Unraveling the Effects of Acute Inflammation on Pharmacokinetics: A Model-Based Analysis Focusing on Renal Glomerular Filtration Rate and Cytochrome P450 3A4-Mediated Metabolism

BACKGROUND AND OBJECTIVES: Acute inflammation caused by infections or sepsis can impact pharmacokinetics. We used a model-based analysis to evaluate the effect of acute inflammation as represented by interleukin-6 (IL-6) levels on drug clearance, focusing on renal glomerular filtration rate (GFR) and cytochrome P450 3A4 (CYP3A4)-mediated metabolism.

METHODS

A physiologically based model incorporating renal and hepatic drug clearance was implemented. Functions correlating IL-6 levels with GFR and in vitro CYP3A4 activity were derived and incorporated into the modeling framework. We then simulated treatment scenarios for hypothetical drugs by varying the IL-6 levels, the contribution of renal and hepatic drug clearance, and protein binding. The relative change in observed area under the concentration-time curve (AUC) was computed for these scenarios.

RESULTS

Inflammation showed opposite effects on drug exposure for drugs eliminated via the liver and kidney, with the effect of inflammation being inversely proportional to the extraction ratio (ER). For renally cleared drugs, the relative decrease in AUC was close to 30% during severe inflammation. For CYP3A4 substrates, the relative increase in AUC could exceed 50% for low-ER drugs. Finally, the impact of inflammation-induced changes in drug clearance is smaller for drugs with a larger unbound fraction.

CONCLUSION

This analysis demonstrates differences in the impact of inflammation on drug clearance for different drug types. The effects of inflammation status on pharmacokinetics may explain the inter-individual variability in pharmacokinetics in critically ill patients. The proposed model-based analysis may be used to further evaluate the effect of inflammation, i.e., by incorporating the effect of inflammation on other drug-metabolizing enzymes or physiological processes.

Use of Physiologically Based Pharmacokinetic Modeling for Hepatically Cleared Drugs in Pregnancy: Regulatory Perspective

Physiologically based pharmacokinetic modeling could be used to predict changes in exposure during pregnancy and possibly inform medicine use in pregnancy in situations in which there is currently limited or no available clinical PK data. The Medicines and Healthcare Product Regulatory Agency has been evaluating the available models for a number of medicines cleared by hepatic clearance mechanisms. Models were evaluated for metoprolol, tacrolimus, clindamycin, ondansetron, phenytoin, caffeine, fluoxetine, clozapine, carbamazepine, metronidazole, and paracetamol. The hepatic metabolism through cytochrome P450 (CYP) contributes significantly to the elimination of these drugs, and available knowledge of CYP changes during pregnancy has been implemented in the existing pregnancy physiology models. In general, models were able to capture trends in exposure changes in pregnancy to some extent, but the magnitude of pharmacokinetic change for these hepatically cleared drugs was not captured in each case, nor were models always able to capture overall exposure in the populations. A thorough evaluation was hampered by the lack of clinical data for drugs cleared by a specific clearance pathway. The limited clinical data, as well as complex elimination pathways involving CYPs, uridine 5'-diphospho-glucuronosyltransferase and active transporter for many drugs, currently limit the confidence in the prospective use of the models. Pregnancy-related changes in uridine 5'-diphospho-glucuronosyltransferase and transport functions are emerging, and incorporation of such changes in current physiologically based pharmacokinetic modeling software is in progress. Filling this gap is expected to further enhance predictive performance of models and increase the confidence in predicting PK changes in pregnant women for hepatically cleared drugs.

Ways to Improve Insights into Clindamycin Pharmacology and Pharmacokinetics Tailored to Practice

Given the increase in bacterial resistance and the decrease in the development of new antibiotics, the appropriate use of old antimicrobials has become even more compulsory. Clindamycin is a lincosamide antibiotic approved for adults and children as a drug of choice for systemic treatment of staphylococcal, streptococcal, and gram-positive anaerobic bacterial infections. Because of its profile and high bioavailability, it is commonly used as part of an oral multimodal alternative for prolonged parenteral antibiotic regimens, e.g., to treat bone and joint or prosthesis-related infections. Clindamycin is also frequently used for (surgical) prophylaxis in the event of beta-lactam allergy. Special populations (pediatrics, pregnant women) have altered cytochrome P450 (CYP)3A4 activity. As clindamycin is metabolized by the CYP3A4/5 enzymes to bioactive N-demethyl and sulfoxide metabolites, knowledge of the potential relevance of the drug’s metabolites and disposition in special populations is of interest. Furthermore, drug–drug interactions derived from CYP3A4 inducers and inhibitors, and the data on the impact of the disease state on the CYP system, are still limited. This narrative review provides a detailed survey of the currently available literature on pharmacology and pharmacokinetics and identifies knowledge gaps (special patient population, drug–drug, and drug–disease interactions) to describe a research strategy for precision medicine.

Comparative Efficacy of Different Oral Doses of Clindamycin in Preventing Post-Operative Sequelae of Lower Third Molar Surgery—A Randomized, Triple-Blind Study

Background and Objectives. Antibiotic regimen optimization is a major concern in post extraction sequelae management following third molar surgery, mostly owing to the absence of universal guidelines. Hence, this study aimed to determine the effect of antibiotic prophylaxis using three different doses of clindamycin on the prevention of infection and other complications following mandibular third molar disimpaction. The secondary outcome was testing whether clindamycin exhibits activity in acute or chronic models of pain using the visual analog scale of pain and the necessity for post-operative rescue analgesia. The tertiary outcome was to assess clindamycin penetration into the saliva by measuring its concentration using liquid chromatography/electrospray ionization tandem mass spectrometry. Materials and Methods. A randomized, two-center, triple-blind, controlled clinical trial was conducted, in which the patients were randomly allocated to three groups: I, receiving 150 mg clindamycin every 8 h; II, receiving 300 mg clindamycin every 8 h; and III, receiving 600 mg clindamycin every 12 h. Each group continued the therapy for five days. Results. An overall decrease in the risk of infection and other post-operative complications, such as trismus, edema, dysphagia, and lymphadenopathy, was achieved, with the best results in group I. Conclusion. As no statistical association was observed between clindamycin concentration in saliva and degree of post-operative inflammation, clindamycin concentration, or pain intensity, smaller doses of clindamycin administered over shorter time periods is recommended.

Influence of Inflammation on Cytochromes P450 Activity in Adults: A Systematic Review of the Literature

Background: Available in-vitro and animal studies indicate that inflammation impacts cytochromes P450 (CYP) activity via multiple and complex transcriptional and post-transcriptional mechanisms, depending on the specific CYP isoforms and the nature of inflammation mediators. It is essential to review the current published data on the impact of inflammation on CYP activities in adults to support drug individualization based on comorbidities and diseases in clinical practice. Methods: This systematic review was conducted in PubMed through 7th January 2021 looking for articles that investigated the consequences of inflammation on CYP activities in adults. Information on the source of inflammation, victim drugs (and CYPs involved), effect of disease-drug interaction, number of subjects, and study design were extracted. Results: The search strategy identified 218 studies and case reports that met our inclusion criteria. These articles were divided into fourteen different sources of inflammation (such as infection, autoimmune diseases, cancer, therapies with immunomodulator…). The impact of inflammation on CYP activities appeared to be isoform-specific and dependent on the nature and severity of the underlying disease causing the inflammation. Some of these drug-disease interactions had a significant influence on drug pharmacokinetic parameters and on clinical management. For example, clozapine levels doubled with signs of toxicity during infections and the concentration ratio between clopidogrel's active metabolite and clopidogrel is 48-fold lower in critically ill patients. Infection and CYP3A were the most cited perpetrator of inflammation and the most studied CYP, respectively. Moreover, some data suggest that resolution of inflammation results in a return to baseline CYP activities. Conclusion: Convincing evidence shows that inflammation is a major factor to be taken into account in drug development and in clinical practice to avoid any efficacy or safety issues because inflammation modulates CYP activities and thus drug pharmacokinetics. The impact is different depending on the CYP isoform and the inflammatory disease considered. Moreover, resolution of inflammation appears to result in a normalization of CYP activity. However, some results are still equivocal and further investigations are thus needed.

Influence of the clindamycin administration route on the magnitude of clindamycin-rifampicin interaction: a prospective pharmacokinetic study

OBJECTIVES

An important clindamycin-rifampicin pharmacokinetic (PK) interaction has been reported, but the potential influence of the clindamycin administration route on that interaction is unknown. This prospective, observational, comparative PK study was undertaken to characterize and analyse the impact of the route, comparing the rifampicin enzyme-inductor effects on clindamycin clearance (CLclin) for oral versus intravenous (IV) administration.

METHODS

Patients with bone-and-joint infections (BJIs) were treated with clindamycin monotherapy (n = 20) or clindamycin-rifampicin combination therapy (n = 19). Patients received continuous IV clindamycin infusion for 2-6 weeks, followed by an oral regimen. Liquid chromatography-mass spectrometry was used to measure plasma clindamycin concentrations at the end of IV and after 2 weeks of oral treatment. The ratios of the mean CLclin for the combination and monotherapy groups were calculated for IV (Riv) and oral (Rpo) routes, with the final ratio, Rf = Rpo/Riv, representing the fold change of the rifampicin-inducing effect from the IV to the oral route.

RESULTS

Comparing monotherapy with combination-therapy groups, the former's median steady-state concentration was two-fold higher after IV administration (8.49 versus 3.82 mg/L, p < 0.001) and its median AUC_0-8h was 12 times higher after oral intake (37.7 versus 3.1 mg.h/L, p < 0.001). Riv, Rpo and Rf were 2.68, 18.8 and 7.0 respectively.

CONCLUSION

The magnitude of this interaction was markedly increased by oral intake, questioning the use of oral treatment for difficult-to-treat infections like BJIs. Nevertheless, the clindamycin-rifampicin combination seems possible provided that clindamycin is administered by continuous IV infusion.

Application of an LC-ESI-QTOF-MS method for evaluating clindamycin concentrations in plasma and prostate microdialysate of rats

Clindamycin is used for infections caused by Gram-positive and Gram-negative anaerobic pathogens and Gram-positive aerobes. Propionibacterium acnes is an important opportunistic microorganism of the human skin and is related to prostatitis. An LC-electrospray ionization-quadrupole time-of-flight-MS method was validated for determining clindamycin concentrations in plasma and prostate microdialysate. Clindamycin separation was carried out on a C₁₈ column at 0.5 mL/min. The mobile phase employed gradient elution of formic acid and methanol. A mass spectrometer was operated in positive electrospray ionization mode to monitor ion 425.1784 and 253.1152 for clindamycin and cimetidine (internal standard), respectively. Linearity was obtained at 0.5-10.0 μg/mL (plasma) and 0.05-1.0 μg/mL (microdialysate) with coefficients of determination ≥0.999. The intra- and inter-day precision (coefficient of variation - CV%) values were ≤13.83% and 12.51% for plasma, respectively, and ≤10.90% and 9.35% for microdialysate, respectively. The accuracy was between 90.82% and 108.25% for plasma, and 96.97% and 106.98% for microdialysate. The present method was fully validated and applied to investigate clindamycin concentrations in both plasma and prostate by microdialysis in Wistar rats (80 mg/kg, intravenous). Because the penetration of antibiotics into the prostate may be restricted, this method allows us to investigate the prostate concentrations of clindamycin for the first time.

Determination of free clindamycin, flucloxacillin or tedizolid in plasma: Pay attention to physiological conditions when using ultrafiltration

Pharmacokinetic/pharmacodynamic indices of anti-infective drugs should be referenced to free drug concentrations. In the present study, clindamycin, flucloxacillin and tedizolid have been determined in human plasma by HPLC-UV. The drugs were separated isocratically within 3-6 min on a C₁₈ column using mixtures of phosphate buffer-acetonitrile of pH 7.1-7.2. Sample treatment for the determination of total drug concentrations in plasma included extraction/back-extraction (clindamycin) or protein precipitation (flucloxacillin, tedizolid). The free drug concentrations were determined after ultrafiltration. An ultrafiltration device with a membrane consisting of regenerated cellulose proved to be suitable for all drugs. Maintaining a physiological pH was crucial for clindamycin, whereas maintaining body temperature was essential for tedizolid. The methods were applied to the analysis of total and free drug concentrations in clinical samples and were sufficiently sensitive for pharmacokinetic studies and therapeutic drug monitoring.

Clindamycin inhibits nociceptive response by reducing tumor necrosis factor-α and CXCL-1 production and activating opioidergic mechanisms

Clindamycin, a bacteriostatic semisynthetic lincosamide, is useful in the management of infections caused by aerobic and anaerobic Gram-positive cocci, including bacteremic pneumonia, streptococcal toxic shock syndrome and sepsis. It has been recently demonstrated that clindamycin inhibits in vitro and in vivo inflammatory cytokine production. In the present study, we investigated the effects of clindamycin in acute and chronic models of pain and inflammation in mice and the underlying mechanisms. Intraperitoneal (i.p.) administration of clindamycin (400 mg/kg) increased the animal's latency to exhibit the nociceptive behavior induced by noxious heat (hot plate model). Intrathecal injection of clindamycin (2, 10 and 50 µg) also increased the animals' latency to exhibit the nociceptive behavior. Tactile hypersensitivity and paw edema induced by intraplantar (i.pl.) injection of carrageenan were attenuated by previous administration of clindamycin (200 and 400 mg/kg, i.p.). Clindamycin (100, 200 and 400 mg/kg, i.p.) also attenuated ongoing tactile hypersensitivity and paw edema induced by i.pl. injection of complete Freund's adjuvant (CFA). The antinociceptive activity of clindamycin (400 mg/kg, i.p.) in the hot plate model was attenuated by previous administration of naltrexone (5 and 10 mg/kg, i.p.), but not glibenclamide or AM251. CFA-induced production of TNF-α and CXCL-1 was reduced by clindamycin (400 mg/kg, i.p.). Concluding, clindamycin exhibits activities in acute and chronic models of pain and inflammation. These effects are associated with reduced production of TNF-α and CXCL-1 and activation of opioidergic mechanisms. Altogether, these results indicate that the clindamycin's immunomodulatory effects may contribute to a pharmacological potential beyond its antibiotic property.

Development of a Pediatric Physiologically-Based Pharmacokinetic Model of Clindamycin Using Opportunistic Pharmacokinetic Data

Physiologically-based pharmacokinetic (PBPK) modeling is a powerful tool used to characterize maturational changes in drug disposition to inform dosing across childhood; however, its use is limited in pediatric drug development. Access to pediatric pharmacokinetic data is a barrier to widespread application of this model, which impedes its development and optimization. To support the development of a pediatric PBPK model, we sought to leverage opportunistically-collected plasma concentrations of the commonly used antibiotic clindamycin. The pediatric PBPK model was optimized following development of an adult PBPK model that adequately described literature data. We evaluated the predictability of the pediatric population PBPK model across four age groups and found that 63-93% of the observed data were captured within the 90% prediction interval of the model. We then used the pediatric PBPK model to optimize intravenous clindamycin dosing for a future prospective validation trial. The optimal dosing proposed by this model was 9 mg/kg/dose in children ≤5 months of age, 12 mg/kg/dose in children >5 months-6 years of age, and 10 mg/kg/dose in children 6-18 years of age, all administered every 8 h. The simulated exposures achieved with the dosing regimen proposed were comparable with adult plasma and tissue exposures for the treatment of community-acquired methicillin-resistant Staphylococcus aureus infections. Our model demonstrated the feasibility of using opportunistic pediatric data to develop pediatric PBPK models, extending the reach of this powerful modeling tool and potentially transforming the pediatric drug development field.

Antibiotic treatment for the sexual partners of women with bacterial vaginosis

BACKGROUND

Bacterial vaginosis (BV) is an infection that has a prevalence between 10% to 50% worlwide. BV results in an imbalance of the normal vaginal flora. Microorganisms associated with BV have been isolated from the normal flora of the male genital tract, and their presence could be related to the recurrence of BV after antibiotic treatment. Therefore, the treatment of sexual partners could decrease the recurrence of infection and possibly the burden of the disease.

OBJECTIVES

To assess the effectiveness in women and the safety in men of concurrent antibiotic treatment for the sexual partners of women treated for BV.

SEARCH METHODS

We searched the Cochrane Sexually Transmitted Infections Group Specialized Register (23 July 2016), CENTRAL (1991 to 23 July 2016), MEDLINE (1946 to 23 July 2016), Embase (1974 to 23 July 2016), LILACS (1982 to 23 July 2016), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (23 July 2016), ClinicalTrials.gov (23 July 2016) and the Web of Science™ (2001 to 23 July 2016). We also handsearched conference proceedings, contacted trial authors and reviewed the reference lists of retrieved studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) that compared the concurrent use of any antibiotic treatment with placebo, no intervention or any other intervention by the sexual partners of women treated for BV.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed trials for inclusion, extracted data and assessed the risk of bias in the included studies. We resolved any disagreements through consensus. We assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

Seven RCTs (1026 participants) met our inclusion criteria, and pharmaceutical industry funded four of these trials. Five trials (854 patients) compared any antibiotic treatment of sexual partners with placebo. Based on high quality evidence, antibiotic treatment does not increase the rate of clinical or symptomatic improvement in women during the first week (risk ratio (RR) 0.99, 95% confidence interval (CI) 0.96 to 1.03; 712 participants, four studies; RR 1.06, 95% CI 1.00 to 1.12; 577 patients, three studies, respectively), between the first and fourth week (RR 1.02, 95% CI 0.94 to 1.11; 590 participants, three studies; RR 0.93, 95% CI 0.84 to 1.03; 444 participants, two studies; respectively) or after the fourth week (RR 0.98, 95% CI 0.90 to 1.07; 572 participants, four studies; RR 1.03, 95% CI 0.90 to 1.17; 296 participants, two studies; respectively). Antibiotic treatment does not led to a lower recurrence during the first and fourth week (RR 1.28, 95% CI 0.68 to 2.43; 218 participants, one study; low quality evidence) or after the fourth week of treatment (RR 1.00, 95% CI 0.67 to 1.52; 372 participants, three studies; low quality evidence) in women, but increases the frequency of adverse events (most frequently gastrointestinal symptoms) reported by sexual partners (RR 2.55, 95% CI 1.55 to 4.18; 477 participants, three studies; low quality evidence). Two trials (172 participants) compared any antibiotic treatment for sexual partners with no intervention. When we compared it with no intervention, the effects of antibiotic treatment on recurrence rate after the fourth week (RR 1.71, 95% CI 0.65 to 4.55; 51 participants, one study), clinical improvement between the first and fourth week (RR 0.93, 95% CI 0.70 to 1.25; 152 participants, two studies) and symptomatic improvement after the fourth week (RR 0.66, 95% CI 0.39 to 1.11; 70 participants, one study) were imprecise and there were no differences between groups. We downgraded the quality of the evidence to low or very low.

AUTHORS' CONCLUSIONS

High quality evidence shows that antibiotic treatment for sexual partners of women with BV, compared with placebo, does not increase the rate of clinical or symptomatic improvement during the first, between the first and fourth or after the fourth week into the women. Low quality evidence suggests that antibiotic treatment does not led to a lower recurrence rate during the first and fourth or after the fourth week of treatment into the women, but increases the frequency of adverse events reported by sexual partners. Finally, compared with no intervention, antibiotic treatment does not decrease the recurrence rate after the fourth week and does not increase the frequency of clinical or symptomatic improvement between the first and fourth or after the fourth week into the women, respectively.

Clindamycin Pharmacokinetics and Safety in Preterm and Term Infants

Clindamycin may be active against methicillin-resistant Staphylococcus aureus, a common pathogen causing sepsis in infants, but optimal dosing in this population is unknown. We performed a multicenter, prospective pharmacokinetic (PK) and safety study of clindamycin in infants. We analyzed the data using a population PK analysis approach and included samples from two additional pediatric trials. Intravenous data were collected from 62 infants (135 plasma PK samples) with postnatal ages of <121 days (median [range] gestational age of 28 weeks [23 to 42] and postnatal age of 17 days [1 to 115]). In addition to body weight, postmenstrual age (PMA) and plasma protein concentrations (albumin and alpha-1 acid glycoprotein) were found to be significantly associated with clearance and volume of distribution, respectively. Clearance reached 50% of the adult value at PMA of 39.5 weeks. Simulated PMA-based intravenous dosing regimens administered every 8 h (≤32 weeks PMA, 5 mg/kg; 32 to 40 weeks PMA, 7 mg/kg; >40 to 60 weeks PMA, 9 mg/kg) resulted in an unbound, steady-state concentration at half the dosing interval greater than a MIC for S. aureus of 0.12 μg/ml in >90% of infants. There were no adverse events related to clindamycin use. (This study has been registered at ClinicalTrials.gov under registration no. NCT01728363.).

Interethnic differences in pharmacokinetics of antibacterials

BACKGROUND

Optimal antibacterial dosing is imperative for maximising clinical outcome. Many factors can contribute to changes in the pharmacokinetics of antibacterials to the extent where dose adjustment may be needed. In acute illness, substantial changes in important pharmacokinetic parameters such as volume of distribution and clearance can occur for certain antibacterials. The possibility of interethnic pharmacokinetic differences can further complicate attempts to design an appropriate dosing regimen. Factors of ethnicity, such as genetics, body size and fat distribution, contribute to differences in absorption, distribution, metabolism and elimination of drugs. Despite extensive previous work on the altered pharmacokinetics of antibacterials in some patient groups such as the critically ill, knowledge of interethnic pharmacokinetic differences for antibacterials is limited.

OBJECTIVES

This systematic review aims to describe any pharmacokinetic differences in antibacterials between different ethnic groups, and discuss their probable mechanisms as well as any clinical implications.

METHODS

We performed a structured literature review to identify and describe available data of the interethnic differences in the pharmacokinetics of antibacterials.

RESULTS

We found 50 articles that met our inclusion criteria and only six of these compared antibacterial pharmacokinetics between different ethnicities within the same study. Overall, there was limited evidence available. We found that interethnic pharmacokinetic differences are negligible for carbapenems, most β-lactams, aminoglycosides, glycopeptides, most fluoroquinolones, linezolid and daptomycin, whereas significant difference is likely for ciprofloxacin, macrolides, clindamycin, tinidazole and some cephalosporins. In general, subjects of Asian ethnicity achieve drug exposures up to two to threefold greater than Caucasian counterparts for these antibacterials. This difference is caused by a comparatively lower volume of distribution and/or drug clearance.

CONCLUSION

Interethnic pharmacokinetic differences of antibacterials are likely; however, the clinical relevance of these differences is unknown and warrants further research.

Oral clindamycin causing acute cholestatic hepatitis without ductopenia: a brief review of idiosyncratic drug-induced liver injury and a case report

Clindamycin is a lincosamide antibiotic active against most of the anaerobes, protozoans, and Gram-positive bacteria, including community-acquired methicillin-resistant Staphylococcus aureus. Its use has increased greatly in the recent past due to wide spectrum of activity and good bioavailability in oral form. Close to 20% of the patients taking clindamycin experience diarrhea as the most common side effect. Hepatotoxicity is a rare side effect. Systemic clindamycin therapy has been linked to two forms of hepatotoxicity: transient serum aminotransferase elevation and an acute idiosyncratic liver injury that occurs 1–3 weeks after starting therapy. This article is a case report of oral clindamycin induced acute symptomatic cholestatic hepatitis and a brief review of the topic.

Use of opportunistic clinical data and a population pharmacokinetic model to support dosing of clindamycin for premature infants to adolescents

Clindamycin is commonly prescribed to treat children with skin and skin-structure infections (including those caused by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA)), yet little is known about its pharmacokinetics (PK) across pediatric age groups. A population PK analysis was performed in NONMEM using samples collected in an opportunistic study from children receiving i.v. clindamycin per standard of care. The final model was used to optimize pediatric dosing to match adult exposure proven effective against CA-MRSA. A total of 194 plasma PK samples collected from 125 children were included in the analysis. A one-compartment model described the data well. The final model included body weight and a sigmoidal maturation relationship between postmenstrual age (PMA) and clearance (CL): CL (l/h) = 13.7 × (weight/70)(0.75) × (PMA(3.1)/(43.6(3.1) + PMA(3.1))); V (l) = 61.8 × (weight/70). Maturation reached 50% of adult CL values at ~44 weeks PMA. Our findings support age-based dosing.

Interspecies allometric scaling of antimalarial drugs and potential application to pediatric dosing

Pharmacopeial recommendations for administration of antimalarial drugs are the same weight-based (mg/kg of body weight) doses for children and adults. However, linear calculations are known to underestimate pediatric doses; therefore, interspecies allometric scaling data may have a role in predicting doses in children. We investigated the allometric scaling relationships of antimalarial drugs using data from pharmacokinetic studies in mammalian species. Simple allometry (Y = a × W(b)) was utilized and compared to maximum life span potential (MLP) correction. All drugs showed a strong correlation with clearance (CL) in healthy controls. Insufficient data from malaria-infected species other than humans were available for allometric scaling. The allometric exponents (b) for CL of artesunate, dihydroartemisinin (from intravenous artesunate), artemether, artemisinin, clindamycin, piperaquine, mefloquine, and quinine were 0.71, 0.85, 0.66, 0.83, 0.62, 0.96, 0.52, and 0.40, respectively. Clearance was significantly lower in malaria infection than in healthy (adult) humans for quinine (0.07 versus 0.17 liter/h/kg; P = 0.0002) and dihydroartemisinin (0.81 versus 1.11 liters/h/kg; P = 0.04; power = 0.6). Interpolation of simple allometry provided better estimates of CL for children than MLP correction, which generally underestimated CL values. Pediatric dose calculations based on simple allometric exponents were 10 to 70% higher than pharmacopeial (mg/kg) recommendations. Interpolation of interspecies allometric scaling could provide better estimates than linear scaling of adult to pediatric doses of antimalarial drugs; however, the use of a fixed exponent for CL was not supported in the present study. The variability in allometric exponents for antimalarial drugs also has implications for scaling of fixed-dose combinations.

Current indications for the use of clindamycin: A critical review

OBJECTIVES

To review the literature and develop evidence-based guidelines for the use of the antibiotic clindamycin.

DATA SOURCES

A search of the MEDLINE database for randomized clinical trials, cohort studies and review articles that examine the therapeutic use or potential adverse effects of clindamycin was undertaken for the years 1966 to 1996. In addition, relevant citations obtained from the references cited in the identified reviews, book chapters and antibiotic guidelines were included.

DATA EXTRACTION

Selected articles examining the indications for or adverse effects from the prophylactic or therapeutic use of clindamycin were selected. A level of evidence was assigned to the indication according to published criteria.

DATA SYNTHESIS AND CONCLUSIONS

Randomized clinical trials (level 1 evidence) support the use of clindamycin in a number of common conditions, including preoperative prophylaxis, intra-abdominal infections, recurrent group A streptococcal pharyngitis, Chlamydia trachomatis cervicitis and anaerobic lung infections. Cohort studies (level 2 evidence) support the use of clindamycin for bone and soft tissue infections. Expert opinion (level 3 evidence) supports the use of clindamycin for invasive group A streptococcal infection and the treatment of diabetic foot infections. Clindamycin's disadvantages are its high cost, the common occurrence of rash and the predisposition of patients taking clindamycin to Clostridium difficile-associated colitis. Based on cohort studies, the risk of severe diarrhea in out-patients is as low as one per 1000, but the risk of in-patients acquiring C difficile colonization may be as high as 30%.

Pharmacokinetics and ex vivo antimalarial activity of artesunate-azithromycin in healthy volunteers

In 18 male healthy subjects, artesunate (200 mg)-azithromycin (1,500 mg) daily for 3 days was found to be well tolerated, with only mild gastrointestinal disturbances reported. The pharmacokinetic properties of artesunate-azithromycin given in combination are comparable to those of the drugs given alone. Artesunate and its major active metabolite, dihydroartemisinin, are responsible for most of the ex vivo antimalarial activity, with a delayed contribution by azithromycin.

Pharmacokinetics of clindamycin in pregnant women in the peripartum period

The study presented here was performed to determine the pharmacokinetics of intravenously administered clindamycin in pregnant women. Seven pregnant women treated with clindamycin were recruited. Maternal blood and arterial and venous umbilical cord blood samples were obtained. Maternal clindamycin concentrations were analyzed by nonlinear mixed-effects modeling with the NONMEM program. The data were best described by a linear three-compartment model. The clearance and the volume of distribution at steady state were 10.0 liters/h and 6.32 x 10(3) liters, respectively. Monte Carlo simulations were performed to determine the area under the concentration curve (AUC) for the free (unbound) drug (f) in maternal serum for 24 h divided by the MIC (fAUC(0-24)/MIC). At a MIC of 0.5 mg/liter, which is the EUCAST breakpoint, the attainment at the lower 95% confidence interval (CI) was 24.6 if the level of protein binding was 65%, and this value concurred well with the target value of 27. However, for higher degrees of protein binding, as has been described in the literature, the attainment was lower, down to 10.2 for a protein binding level of 85% (lower 95% CI). The concentrations in umbilical cord blood were lower than those in maternal blood. The concentration-time profiles in maternal serum indicate that the level of exposure to clindamycin may be too low in these patients. Together with the lower concentrations in umbilical cord blood, this finding suggests that the current dosing regimen may not be adequate to protect all neonates from group B streptococcal disease.

Evaluation of gender in the oral pharmacokinetics of clindamycin in humans

Clindamycin is an antimicrobial agent metabolized by CYP3A4. Gender may influence the pharmacokinetics of drugs metabolized by this pathway, however, no information about differences in the pharmacokinetics of clindamycin in men and women is available. The purpose of this study was to evaluate gender differences in clindamycin oral pharmacokinetics. Twenty-four subjects (11 men and 13 women) received an oral 600 mg dose of clindamycin under fasting conditions and plasma concentrations were obtained at selected times during 12 h. Increased plasma levels were observed in women, but when the dose was normalized by the body weight of individuals, these differences disappeared, indicating that gender does not play an important role in the pharmacokinetics of this drug.

Dose-independent pharmacokinetics of clindamycin after intravenous and oral administration to rats: Contribution of gastric first-pass effect to low bioavailability

The pharmacokinetic parameters of clindamycin were evaluated after intravenous (at doses of 50, 100, and 200mg/kg) and oral (at doses of 75, 150, and 300mg/kg) administration of the drug to rats. The first-pass effect of clindamycin was also evaluated after intraportal, intragastric, and intraduodenal administration of the drug at a dose of 150mg/kg to rats. After both intravenous and oral administration of clindamycin, the pharmacokinetic parameters of the drug were dose-independent. Hence, the extent of absolute oral bioavailability (F) was also independent of oral doses. After oral administration of clindamycin (150mg/kg), 7.68% of oral dose was not absorbed up to 24h and F value was 28.2%. The gastric first-pass effect of clindamycin was 60.7% of oral dose. The first-pass effects of clindamycin in the lung, heart, intestine, and liver were almost negligible, if any, in rats. The low F of clindamycin in rats was mainly due to considerable gastric first-pass effect. Clindamycin was stable in rat gastric juice and various buffer solutions having pHs ranging from 1 to 13. The plasma-to-blood cells partition ratio of clindamycin was 7.59 in rat blood. The plasma protein binding of clindamycin in rats was 67.5%.

Separation and characterization of clindamycin and related impurities in bulk drug by high-performance liquid chromatography-electrospray tandem mass spectrometry

A simple high-performance liquid-electrospray ionization tandem mass spectrometric (HPLC-ESI-MSn) method has been developed for the rapid identification of clindamycin and its related minor impurities in bulk drug. The ESI-MSn results obtained allowed us to propose plausible schemes for their fragmentations, which were confirmed further by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) using collision-induced dissociation (CID) method at high mass resolution. The positive ESI-MS/MS of clindamycin and its derivative compounds showed some diagnostic fragments, such as the neutral losses of H2O, HCl, methanethiol and 2-methylthio-ethenol, and the residue of 3-propyl-N-methylpyrrolidine and 3-ethyl-N-methylpyrrolidine, which are specific and useful for the identification of the lincosamide antibiotics and related impurities. According to the fragmentation mechanism of mass spectrometry and HPLC-UV-ESI-MSn data, six impurities of clindamycin have been identified on-line. Additionally, the positive ion mode extracted ion current (EIC) method has been used to separate and identify these lincosamide compounds.

[Pharmacokinetic/pharmacodynamic analysis of antibiotic therapy in dentistry and stomatology]

INTRODUCTION

This study evaluates the efficacy of various antimicrobial treatments for orofacial infections on the basis of pharmacokinetic/pharmacodynamic (PK/PD) criteria.

METHODS

A complete a literature search was undertaken to establish the MIC90 values of the five microorganisms most frequently isolated in odontogenic infections and the pharmacokinetic parameters of 13 antibiotics used in these infections. Pharmacokinetic simulations were then carried out with mean population parameters and efficacy indexes were calculated for the 47 treatment regimens analyzed. For drugs showing time-dependent antibacterial killing, the time above MIC (t > MIC) was calculated. For drugs with concentration-dependent bactericidal activity, the AUC/MIC was calculated.

RESULTS

Amoxicillin-clavulanic (500 mg/8 h or 1000 mg/12 h) and clindamycin (300 mg/6 h) in the time-dependent killing group and moxifloxacin (400 mg/24 h) in the concentration-dependent group showed adequate efficacy indexes against the five pathogens considered to be the most commonly implicated in odontogenic infections. The spiramycin plus metronidazole combination, present in the commercial formulation Rhodogyl, did not reach satisfactory PK/PD indexes.

CONCLUSION

PK/PD indexes, which are useful predictors of the potential efficacy of antibacterial therapy, were used with ontogenic infections in the present study. The PK/PD simulations showed that amoxicillin-clavulanic, clindamycin and moxifloxacin were the most suitable antibiotics for this kind of infection. Clinical trials are required to confirm that this methodology is useful in these pathologic processes.

Simple method for the assay of clindamycin in human plasma by reversed-phase high-performance liquid chromatography with UV detector

A rapid and simple high-performance liquid chromatography (HPLC) method was developed and validated for the quantification of clindamycin in human plasma. After precipitation with 50% trichloroacetic acid (TCA) containing the internal standard, propranolol, the analysis of the clindamycin level in the plasma samples was carried out using a reverse-phase cyano (CN) column with ultraviolet detection (204 nm). The chromatographic separation was accomplished with an isocratic mobile phase consisting of acetonitrile-distilled water-7.6 mm tetramethylammonium chloride (TMA) (60:40:0.075, v/v/v), adjusted to pH 3.2. The proposed method was specific and sensitive with a lower limit of quantitation (LLOQ) of 0.2 microg/mL. This HPLC method was validated by examining the precision and accuracy for inter- and intraday analysis in the concentration range 0.2-20.0 microg/mL. The relative standard deviations (RSD) in the inter- and intraday validation were 6.1-14.9 and 6.0-16.1%, respectively. In the stability test, clindamycin was found to be stable in human plasma during the storage and assay procedure. The present HPLC method was applied to the analysis of samples taken up to 12 h after a single oral administration of clindamycin in healthy volunteers.

Pharmacokinetic/Pharmacodynamic Evaluation of Antimicrobial Treatments of Orofacial Odontogenic Infections

OBJECTIVE

To evaluate the efficacy of antimicrobial therapy in oral odontogenic infections using estimated pharmacokinetic/pharmacodynamic parameters or efficacy indices, and to compare pharmacokinetic/pharmacodynamic breakpoints with National Committee for Clinical Laboratory Standards' (NCCLS) breakpoints.

STUDY DESIGN

Retrospective literature search to obtain minimum inhibitory concentration (MIC) values, pharmacokinetic parameters of antimicrobials and NCCLS breakpoints. Pharmacokinetic simulations were carried out using WinNonlin software (Pharsight Corporation, Mountain View, CA, USA).

METHODS

For antimicrobials with time-dependent activity, the time that the plasma drug concentration exceeds the MIC as the percentage of dose interval at steady state was calculated. For antimicrobials with concentration-dependent activity, the total area under the plasma concentration-time curve over 24 hours at steady state divided by the MIC was calculated. Pharmacokinetic/pharmacodynamic breakpoints were calculated according to these parameters.

RESULTS

Only amoxicillin/clavulanic acid and clindamycin showed adequate efficacy indices against the most commonly isolated bacteria in odontogenic infections. Metronidazole reached good indices against anaerobes only. Pharmacokinetic/pharmacodynamic susceptibility breakpoints do not coincide exactly with NCCLS breakpoints.

CONCLUSION

Owing to the scarcity of double-blind, clinical trials on the use of antimicrobials in endodontics, this study may be useful in determining the best antimicrobial treatment in these infections. However, as we have not used concentration data in infected tissue to determine pharmacokinetic/pharmacodynamic indices, it would be necessary to design clinical trials in order to confirm these results.

In vitro activity and interaction of clindamycin combined with dihydroartemisinin against Plasmodium falciparum

Combination regimens are considered a valuable tool for the fight against drug-resistant falciparum malaria. This study was conducted to evaluate the antimalarial potential of clindamycin in combination with dihydroartemisinin in continuously cultured and in freshly isolated Plasmodium falciparum parasites, measuring the inhibition of Plasmodium falciparum histidine-rich protein II synthesis. Interaction analysis revealed a synergistic or additive mode of interaction at various concentration ratios in all continuously cultured parasites at the 50% effective concentration (EC(50)) level. Antagonism was not found for any of the culture-adapted parasites. In fresh P. falciparum isolates, a fixed clindamycin-dihydroartemisinin combination exhibited additive activity at the EC(50) and EC(90) levels. The drug mixture showed no significant activity correlation to other commonly used antimalarials. The clindamycin-dihydroartemisinin combination appears to be a promising candidate for clinical investigation.

A new HPLC/UV method for the determination of clindamycin in dog blood serum

A new HPLC method for the quantitative determination of clindamycin in dog blood serum at levels down to 80 ng/ml has been developed. Samples were deproteinised with acetonitrile and clindamycin was extracted with dichloromethane. Chromatographic analysis was carried out on a C(18) reversed-phase analytical column in the presence of tetra-n-butylammonium hydrogen sulfate (TBA), as an ion-pairing agent. UV detector wavelength was set at 195 nm. The assay was validated for a concentration range from 80 to 6000 ng/ml serum. Good linearity was observed in the entire concentration range. The limit of quantification (LOQ) was 80 ng/ml and the limit of detection (LOD) was 60 ng/ml. Regression of accuracy data yielded an overall mean recovery value (+/-S.E.M.) of 93.98+/-0.42%, while precision data revealed coefficient of variation (CV (%)) values lower than 4.41%. The method was successfully applied to determine drug concentrations in serum samples from dogs that had been orally administered clindamycin hydrochloride.

Therapeutic drug monitoring in HIV infection: current status and future directions

BACKGROUND

Highly active antiretroviral therapy (HAART) can suppress viral replication and prolong patient life substantially. However, HAART can fail for a number of reasons, including incomplete adherence, pharmacokinetic factors and the emergence of resistance. Because the number of possible antiretroviral combinations is limited, the use of existing treatment options must be optimized. Whether the application of therapeutic drug monitoring (TDM) in routine clinical practice may help with this purpose remains a subject of debate. However, TDM has been introduced in some centres despite the lack of guidelines for optimal use of this test.

OBJECTIVE

In October 2000, a panel of experts met in Perugia, Italy, to discuss the key issues surrounding the introduction of TDM into routine clinical practice. The purpose of the meeting was to achieve a consensus among panel members on the following issues: (i) validity of data suggesting the utility of TDM in HAART; (ii) patient categories and clinical settings in which TDM may be of most benefit; (iii) target levels of antiretroviral agents; (iv) influence of covariables on target levels of drugs; (v) blood sampling and dosage adjustment strategies; and (vi) future research steps needed to elucidate issues regarding the applicability of TDM in clinical practice.

OUTCOME

This report, which has been updated to include data published or presented at conferences up to the end of August 2001, summarizes the data presented and issues discussed at the meeting. This article will guide the reader through the data and discussions that have allowed the panel to formulate a series of position statements regarding the current status and future applications of TDM in antiretroviral therapy. These statements have been formulated to provide suggestions for the design of future TDM clinical trials, as well as to provide useful points of reflection for centres in which TDM is already in use.

Oral bioavailability and pharmacokinetics of trovafloxacin in patients with AIDS

Trovafloxacin pharmacokinetics were evaluated in 12 subjects with AIDS. By using a randomized design, single 200-mg doses of oral trovafloxacin and intravenous alatrofloxacin were administered. The mean absolute bioavailability was 91%. The pharmacokinetics of trovafloxacin when administered orally as the active form or intravenously as the prodrug (alatrofloxacin) are not altered in subjects with AIDS compared to those in healthy adults.

Pharmacokinetics of rifabutin in HIV-infected patients with or without wasting syndrome

AIMS

The purpose of the study was to compare the pharmacokinetic parameters of rifabutin obtained in a group of patients without wasting syndrome (NWS) with those obtained in a group with wasting syndrome (WS).

METHODS

A single dose of 300 mg rifabutin was administered in the fasting state to the patients in both study groups and blood samples were scheduled to be collected at the following times: 0 (predose), 0.5, 1, 2, 3, 4, 6, 8, 24, 48, 72 and 96 h following administration. Data were analysed using noncompartmental methods. The pharmacokinetic parameters of rifabutin in patients with and without wasting syndrome were compared using the Mann-Whitney U-test.

RESULTS

Cmax was 0.34+/-0. 14 mg l-1 in NWS patients and 0.55+/-0.16 mg l-1 (P=0.01) in patients with WS. tmax was 4.2+/-1.5 and 3.3+/-2.3 h (P=0.17) in NWS and WS patients, respectively. The AUCs were similar in the two study groups. V/F was 2905+/-1646 l in NWS patients and 1701+/-492 l (P=0.07) for the WS group. These differences are less pronounced following normalization of V/F to patients body weight (43.7+/-20.1 vs 35.4+/-10.3 l kg-1 ). t1/2,lambdaz tended to be shorter in patients with WS (31.4+/-12.9 vs 46.0+/-23.5 h, P=0.12).

CONCLUSIONS

Our study suggests that the pharmacokinetics of rifabutin in patients with wasting syndrome are not altered to a degree that is clinically important.

The relationship between ritonavir plasma levels and side-effects: implications for therapeutic drug monitoring

OBJECTIVES

To assess whether the neurological or gastrointestinal adverse effects of ritonavir correlate with parameters of ritonavir systemic exposure.

METHODS

Peak (Cmax) and trough (Cmin) ritonavir plasma levels were compared in 11 patients experiencing side-effects (group A) versus 10 patients without side-effects (group B). Ritonavir was administered with the following escalation dosing scheme: 300, 400, 500 mg twice a day for 3, 4, and 5 days, respectively, then the full dose of 600 mg twice a day. Blood sampling was done in group A within 24 h of the occurrence of side-effects and in group B after at least 3 days of the full dosage regimen.

RESULTS

Both Cmax and Cmax were significantly higher (Mann-Whitney U test) in patients with side-effects. Cmax was [median (interquartile range)] 26.7 (22.7-33.3) mg/l versus 16.2 (13.4-17.0) mg/l (P = 0.001) and Cmin was 12.6 (9.1-13.9) versus 7.5 (4.9-8.6) mg/l (P = 0.002).

CONCLUSION

Patients with higher ritonavir concentrations are at a higher risk of experiencing neurological or gastrointestinal side-effects. Individualization of the dosage regimen, e.g. a downward titration of the ritonavir dose in patients with side-effects, guided by plasma level monitoring, may result in a substantial increase in the percentage of patients tolerating ritonavir without increasing the risk of treatment failure as a result of suboptimal systemic exposure.

Systemic absorption of clindamycin after intravaginal administration of clindamycin phosphate ovule or cream

The absolute bioavailability of clindamycin phosphate vaginal ovule with comparison to a reference treatment of clindamycin phosphate sterile solution, as well as the relative bioavailability of the ovule compared to clindamycin phosphate vaginal cream, was evaluated in 12 healthy adult female volunteers. Subjects were randomly assigned to receive either the ovule or cream formulation intravaginally for 3 consecutive days during the two-way crossover portion of the study. During a third treatment period, all subjects received 100 mg of clindamycin as a 4-minute intravenous infusion of clindamycin phosphate sterile solution (10 mg/mL). Clindamycin concentrations in serum were assayed by a high-performance liquid chromatography method with detection by mass spectrometry. Pharmacokinetic analyses of the serum data indicated low systemic absorption of clindamycin from the vaginal cream (about 4%), consistent with results of previous bioavailability studies. Following intravaginal administration of the clindamycin phosphate ovule, systemic absorption averaged 30%, which was approximately sevenfold greater than after dosing with the vaginal cream. The higher drug absorption for the ovule may be related to differences in formulation effects on the vaginal membrane. Nevertheless, systemic exposure to clindamycin from the ovule is still considerably lower than from a therapeutic oral dose.

Determination of clindamycin in human plasma by high-performance liquid chromatography using coupled columns

A rapid automated method has been developed for the determination of clindamycin, a lincosamide antibiotic, in human plasma. Coupled column HPLC was used after precipitation of plasma proteins with a saturated ammonium sulfate solution. As a first step, the drug and internal standard were trapped on a precolumn of LiChrospher 60RP-select B. A reversed-phase Nucleosil 100 C18 HD column then separated drug and internal standard from each other and from remaining plasma components. The assay was validated in the range 0.2-10.0 micrograms ml-1 plasma. The results obtained for accuracy, intra- and inter-day precision complied very well with the generally accepted criteria for bioanalytical assays.

Penetration of clindamycin and its metabolite N-demethylclindamycin into cerebrospinal fluid following intravenous infusion of clindamycin phosphate in patients with AIDS

Clindamycin, which is usually used in combination with pyrimethamine, has been proven effective in the treatment of cerebral toxoplasmosis in human immunodeficiency virus-infected patients. However, it is not known if clindamycin achieves inhibitory concentrations at the site of infection. Also, it has been hypothesized that the activity of clindamycin against Toxoplasma gondii may be due, at least in part, to a metabolite. We evaluated the penetration of clindamycin and its major metabolite, N-demethylclindamycin (NDC), into cerebrospinal fluid (CSF) of AIDS patients undergoing lumbar puncture for diagnostic purposes. A single, 1,200-mg dose of clindamycin was administered as a 45-min intravenous infusion beginning at 1.5 or 2.5 h before CSF sampling. The concentrations of clindamycin in CSF ranged from 0.091 to 0.429 mg/liter at 1.5 h and from 0.120 to 0.283 mg/liter at 2.5 h following the beginning of the infusion. The concentrations of clindamycin in CSF were well above the 50% inhibitory concentration of 0.001 mg/liter and the parasiticidal concentration of 0.006 mg/liter. NDC was undetectable both in plasma and in CSF. Our study provides a pharmacokinetic rationale for the clinical efficacy of clindamycin in the treatment of cerebral toxoplasmosis.

Population pharmacokinetics of rifabutin in human immunodeficiency virus-infected patients

Rifabutin pharmacokinetics were studied by the population approach (NONMEM) with 40 human immunodeficiency virus-infected patients receiving rifabutin at different doses for prophylaxis or therapy of mycobacterial infections. A two-compartment open model with first-order absorption was used as the structural pharmacokinetic model. Parameter estimates were the absorption rate constant (0. 201/h), clearance/bioavailability (CL/F; 60.9 liters/h), volume of the central compartment/bioavailability (231 liters), intercompartmental clearance (60.3 liters/h), and volume of the peripheral compartment/bioavailability (Vp/F; 1,050 liters). The distribution and elimination half-lives were 1.24 and 25.4 h, respectively. The covariates tested for influence on CL/F and Vp/F were sex, age, weight, height, body surface area, tobacco smoking, drug addiction, alanine aminotransferase levels, creatinine clearance, total protein, bilirubin, numbers of CD4(+) cells, presence of diarrhea, cachexia index, rifabutin use (prophylaxis versus therapy), rifabutin dose, study site, and the concomitant administration of clarithromycin, fluconazole, phenobarbital, ciprofloxacin, azithromycin, or benzodiazepines. The only statistically significant effects on rifabutin pharmacokinetic parameters were a 27% decrease in Vp/F due to the concomitant administration of azithromycin and a 39% increase in Vp/F due to tobacco smoking. Such effects may be considered clinically unimportant. Our results confirm the lack of a correlation of rifabutin pharmacokinetic parameters with parameters of disease progression and gastrointestinal function. Also, the lack of a correlation with covariates which were previously found to be significant, such as concomitant fluconazole and clarithromycin use, may suggest that the effect of such covariates may be less important in the real clinical setting, in which several concomitant factors may influence pharmacokinetic parameters, with an overall effect of no apparent correlation.

Oral bioavailability and pharmacokinetics of ciprofloxacin in patients with AIDS

Few reports on the effects of AIDS on the absorption of orally (p.o.) administered agents exist. To help fill this informational gap, we administered ciprofloxacin to 12 patients with AIDS by two dosing regimens (400 mg given intravenously [i.v.] and 500 mg given p.o. every 12 h) in a randomized, crossover fashion. Pharmacokinetic parameters were determined by noncompartmental methods. Mean values (+/- standard deviations [SD]) for p.o. ciprofloxacin were as follows: peak concentration of drug in serum (Cmax), 2.94 +/- 0.51 microg/ml; time to Cmax, 1.38 +/- 0.43 h; area under the concentration-time curve from 0 to 12 h (AUC(0-12)), 12.13 +/- 3.21 microg x h/ml; and half-life (t(1/2)), 3.86 +/- 0.48 h. Mean values (+/- SD) for i.v. ciprofloxacin were as follows: Cmax, 3.61 +/- 0.82 microg/ml; time to Cmax, 1.0 h; AUC(0-12), 11.92 +/- 2.92 microg x h/ml; and t(1/2), 3.98 +/- 0.94 h. The mean percent absolute bioavailability for ciprofloxacin was calculated to be 82% +/- 13%, similar to the value for healthy volunteers. We conclude that ciprofloxacin when administered p.o. to patients with AIDS is well absorbed, as evidenced by excellent bioavailability and is not affected by gastrointestinal changes in the absence of infectious gastroenteritis and severe diarrhea.

Bactericidal activity of low-dose clindamycin administered at 8- and 12-hour intervals against Staphylococcus aureus, Streptococcus pneumoniae, and Bacteroides fragilis

Twelve volunteers received 300 mg of clindamycin intravenously (i.v.) or orally (p.o.) administered every 8 h (q8h) or q12h by random assignment over four study periods. Serum bactericidal titers were determined for each regimen against two isolates each of Staphylococcus aureus, Streptococcus pneumoniae (one penicillin-sensitive isolate and one penicillin-resistant isolate), and Bacteroides fragilis. The duration of measurable bactericidal activity over the dosing interval (expressed as a percentage of the dosing interval) was determined for each isolate. No significant differences in the duration of activity were observed between i.v. and p.o. regimens dosed according to the same interval (P > 0.05). All regimens provided bactericidal activity against S. pneumoniae for 100% of their respective dosing intervals. Against B. fragilis, bactericidal activity was observed for greater than 80% of the dosing interval for each of the regimens. Although a statistically significant difference favoring the q8h i.v. regimen (P < 0.05) was detected, this difference is not believed to be clinically significant. The q8h and q12h regimens provided measurable bactericidal activity against S. aureus for greater than 85 and 50% of the dosing intervals, respectively (P < 0.001). Clindamycin dosed at 300 mg i.v. or p.o., q8h or q12h, provides adequate coverage against S. aureus, S. pneumoniae, and B. fragilis.

Role of viral infections in the induction of adverse drug reactions

A spectrum of adverse drug reactions that are caused by the combined action of drugs and viruses has been described: ampicillin rash in acute infectious mononucleosis; Reye's syndrome; hypersensitivity reactions to sulphonamides in patients with HIV infection; drug-induced agranulocytosis; paracetamol (acetaminophen) hepatotoxicity; aspirin (acetylsalicyclic acid)-induced asthma; Epstein-Barr virus-associated lymphoma and methotrexate; and AIDS-related Kaposi's sarcoma and nitrite use. Changes in pharmacokinetics have been reported for: caffeine, sulfamethoxazole and fluconazole in patients with HIV infection; theophylline, following influenza and influenza vaccination; and recently, dipyrone metabolites in carriers of the hepatitis B virus. In addition increased drug- and drug metabolite-related toxicity has been observed in virally infected cells. Pathogenetic mechanisms for the interaction between drugs and viruses are varied, and include biological mechanisms (often immunological) and changes in drug metabolism. The combined effects of chemical and biological exposure provide a unique model for the study of disease induction.

Protein binding of clindamycin in sera of patients with AIDS

Patients with AIDS have altered pharmacokinetics of clindamycin compared with those of healthy control subjects. In an attempt to better understand these differences, we undertook a study of protein binding of clindamycin in sera of patients with AIDS. Fifteen patients with AIDS and 15 healthy volunteers were given a single 600-mg dose of clindamycin orally and intravenously, and serum samples were collected at three time points corresponding to high, midpoint, and low clindamycin concentrations. Protein binding was determined by ultrafiltration, and total and unbound clindamycin concentrations were measured with a gas chromatography assay. AIDS patients had alpha 1-acid glycoprotein values approximately twice those of healthy volunteers (mean +/- standard deviation, 103 +/- 27 versus 61 +/- 11 mg/dl; P = 0.001). Overall, serum protein binding levels were higher in AIDS patients (mean +/- standard deviation, 83 +/- 7 versus 78% +/- 8%; P = 0.0001), which is likely the result of increased alpha 1-acid glycoprotein levels in these patients. Total concentrations of clindamycin in plasma were significantly higher in AIDS patients at most time points studied, while unbound serum clindamycin concentrations did not differ among the groups at each sampling time after both oral and intravenous dosing. Increased protein binding may partly explain the altered pharmacokinetic disposition of clindamycin in AIDS patients; however, other factors cannot be excluded.

Efficacy of clarithromycin versus that of clindamycin for single-dose prophylaxis of experimental streptococcal endocarditis

Clarithromycin is compared with clindamycin for single-dose prophylaxis of streptococcal endocarditis in rats. Human-like kinetics of the two antibiotics prevented endocarditis in animals challenged with both small and large amounts of bacterial inocula. Clarithromycin was marginally superior to clindamycin against small amounts of inocula. Clarithromycin may be considered for endocarditis chemoprophylaxis in human.