Pharmacodynamic Correlations Research Articles

A double-blind, placebo-controlled, efficacy, safety, and pharmacokinetic study of INN 00835, a novel antidepressant peptide, in the treatment of major depression

Background: INN 00835 is a synthetic pentapeptide with a potential for rapid onset of action as an antidepressant. Its efficacy was investigated in a pilot study in patients diagnosed with major depression. Methods: Fifty two patients received either active drug — INN 00835 (26 patients) — or placebo (26 patients), subcutaneously at 0.2 mg/kg for 5 consecutive days. The patients were evaluated for an additional 4 weeks after treatment. Efficacy was evaluated by the following psychiatric rating scales: HAMD, MADRS, CSRS, CGI, and VAS. The effect of treatment was also evaluated by using a biochemical marker: changes in blood platelet serotonin (5HT) uptake rates in drug-treated patients compared to those in the placebo group. Plasma concentrations of INN 00835 were measured by LC/MS. Results: Statistical analysis indicated a strong pharmacodynamic correlation between plasma drug concentrations at 1 h after dosing and the reduction in the severity of depression as measured by the psychiatric rating scales. A minimum effective plasma concentration (MEC) of INN 00835 was 5 ng/ml. Statistically significant differences in response to treatment ( P<0.05) were found between patients with plasma concentrations above MEC and those in the placebo group, as well as between subjects with plasma concentrations above and below the MEC. The peak effect was observed after the 5-day treatment and the response to treatment persisted during the 4-week follow-up period. The change of 5HT uptake rates after treatment was significantly larger in the drug-treated group than in the placebo group. Limitations: This was a pilot study conducted in a relatively small population (52 patients) and the limited number of blood sampling times did not allow a comprehensive pharmacokinetic analysis. There was a relatively large placebo response. The results have to be confirmed in future, large scale studies. Conclusions: INN 00835 appears to be a promising drug for the treatment of major depression.

Assessment of different antibacterial effect measures used in in vitro models of infection and subsequent use in pharmacodynamic correlations for moxifloxacin.

A dilutional culture in vitro pharmacodynamic model of infection was used to assess the best measure of antibacterial effect for moxifloxacin at simulated human doses of 400 mg 24 hourly for 48 h. This was then related to two pharmacodynamic parameters, the drug area under curve: MIC ratio (AUC/MIC) and the length of time that the drug concentration remained above the MIC of the bacterium (T > MIC). Twenty-one bacterial strains (Streptococcus pneumoniae n = 6; Haemophilus influenzae n = 6; Moraxella catarrhalis n = 3; beta-haemolytic streptococci n = 3; Staphylococcus aureus n = 3; MIC range 0.06-3.6 mg/L) were tested in 69 individual simulations. The measures or parameters of antibacterial effect considered were log change in viable count in the initial inoculum at 12 h (triangle up12), 24 h (triangle up24), 36 h (triangle up36), 48 h (triangle up48), maximum reduction in count (triangle up(max)); time for bacterial counts to reduce by 100-fold from the initial density (T99) or 1,000-fold (T99.9); and area under the bacterial kill curve from 0 to 24 h (AUBKC(24)) or from 0 to 48 h (AUBKC(48)). triangle up12, triangle up24, triangle up36, triangle up48, triangle up(max), T99, T99.9 did not vary over the complete range of MICs; at high MICs, especially with Gram-positive bacteria the T99 and T99.9 values were >48 h while at low MICs, especially with Gram-negative bacteria, bacterial counts were reduced below the limit of detection with triangle up12, triangle up24, triangle up36, triangle up48 and triangle up(max) exceeding >6.5 log reduction. AUBKC(24) and AUBKC(48) varied more completely over the range of MICs and more importantly had the best within-strain reproducibility (median percentage coefficient of variation <15%). The relationship between the transformed AUBKC(24) and AUC/MIC could be described by a sigmoid Emax model but the relationship with T > MIC could not. Use of weighted least squares regression to examine the combined effect of AUC/MIC and T > MIC on AUBKC(24) indicated that AUC/MIC provided a good fit to the data (r(2) = 0.94) and adding T > MIC did not improve the model fit. Cox proportional hazards regression indicated that AUC/MIC was predictive of T99 and in a multivariate model although AUC/MIC predicted outcome after fitting AUC/MIC, T > MIC was not significant. AUBKC was thus shown to be the optimum measure of antibacterial effect to use in pharmacodynamic studies of moxifloxacin and AUC/MIC the best predictor of antibacterial effect as measured by AUBKC(24) or T99. These results are in good agreement with animal data on moxifloxacin pharmacodynamics and human data for some other fluoroquinolones.

Pharmacokinetic–pharmacodynamic correlation of lamotrigine, flunarizine, loreclezole, CGP40116 and CGP39551 in the cortical stimulation model

The purpose of this study was to assess the concentration–anti-convulsant effect relationships of a number of anti-convulsant drugs in the direct cortical stimulation model, to obtain more insight in the properties and predictive value of this model. The time course of the effect of lamotrigine, loreclezole, flunarizine, CGP40116 and CGP39551 was determined after iv. administration in conjunction with their pharmacokinetics. Convulsive activity was induced by stimulation of the motor cortex with a ramp-shaped pulse train. This technique allows consecutive measurements of the treshold for localized (TLS) and for generalized (TGS) seizure activity. Increase in threshold was used as measure of the anti-convulsant effect. After administration of lamotrigine, pronounced elevation of the TGS, with little change in the TLS, was observed. Flunarizine caused a similar effect, but much less intense. Loreclezole strongly elevated the TGS and to a lesser extent the TLS, also. The concentration–anti-convulsant effect relationship of the three compounds could be fitted by an exponential model. The NMDA antagonists, CGP40116 and CGP39551, induced minor changes in the TLS and a slight increase in the TGS. The onset of this effect was marked by a delay relative to blood concentrations. The biophase equilibration kinetics was estimated and a linear model was applied to describe the concentration-effect relationship of both NMDA antagonists. The present results show that the cortical stimulation model is a suitable technique for integrated pharmacokinetic-pharmacodynamic modelling and for assessing anti-convulsant efficacy. The results show that the model is rather insensitive to calcium channel blockers and NMDA antagonists.

Cardiac toxicity following high-dose cyclophosphamide, cisplatin, and BCNU (STAMP-I) for breast cancer

We retrospectively evaluated 443 breast cancer patients treated with high-dose cyclophosphamide, cisplatin, and BCNU (STAMP-I) with autologous stem cell support to characterize the cardiac toxicity of this regimen. Patients had stage II-III (n = 243) or stage IV (n = 200) breast cancer. We observed an overall 5.1% incidence of cardiac complications, both clinical and subclinical, in the whole group: 4.9% in stage II-III and 5.5% in stage IV patients. Clinical cardiomyopathy (CMP) was observed in 1.6% of stage II-III patients (1 case of fatal grade 5 toxicity and 3 cases of grade 3 CMP) and in 3.5% of patients with stage IV disease (1 case of grade 4 and 6 cases of grade 3). The incidence of cardiac toxicity did not differ significantly between the groups. Prior radiation therapy to the mediastinum or left chest wall (P = .001) and advanced age (P = .01) were independent predictors of an increased risk of the appearance of this complication. No pharmacodynamic correlation was observed between any of the 3 drugs and cardiac toxicity. Biol Blood Marrow Transplant 2000;6(2A):198-203.

Quantification of Sodium Lauryl Sulfate Penetration into the Skin and Underlying Tissues after Topical Application—Pharmacological and Toxicological Implications

Sodium lauryl sulfate (SLS) is known to penetrate skin and cause cutaneous irritation. Some of these effects have been well‐defined using bioengineering techniques. In this study, the ability of SLS to penetrate skin was quantified in a hairless rat model. In addition, local deep tissue penetration and systemic exposure to SLS were also evaluated to assess the toxic potential of topically applied SLS. SLS was observed to penetrate directly to a depth of about 5–6 mm below the applied site. Systemic redistribution was predominantly responsible in determining concentrations of SLS in tissues deeper than 5–6 mm. Epidermal concentrations of SLS after application of 1% (34 mM) aqueous SLS solution for 24 h were above the threshold levels which are known to evoke typical skin irritation responses. Deeper underlying tissues including dermis, subcutaneous, and muscle may also be exposed to high levels of SLS. Topically applied SLS was also observed in blood and contralateral tissues but the observed levels were not likely to elicit any systemic side effects at these doses. Traces of SLS were observed in tissues 7 days after single 24 h application of SLS, which supports the prolonged barrier disruption data generated using conventional bioengineering techniques. Cumulative treatment of SLS significantly increased the concentration of this compound in the underlying epidermis. The known preferential affinity of SLS for skin lipids and proteins was further confirmed by both in vitro and in vivo results. However, in vitro studies failed to predict the underlying tissue toxicity of SLS under the patch site when compared to the in vivo results. Such quantitative pharmacokinetic–pharmacodynamic correlations may be useful predictors for effective use of surfactants as penetration enhancers in cosmetic, pharmaceutical, and industrial applications.

The experience with suramin in advanced prostate cancer

Suramin is a new experimental polyanionic compound that has shown evidence of antitumor activity in patients with hormone refractory prostate cancer. After a few years of Phase I and Phase II testing, much of the drug's toxicity pattern has been carefully characterized. Similarly, pharmacologic studies have defined many of the drug's complex pharmacologic properties to the extent that simple outpatient methods of drug administration can be easily accomplished. A pharmacologically derived, fixed outpatient schedule has been shown to be safe and effective and is currently in active Phase III development in prostate cancer and will provide more definitive data regarding the role of suramin in the treatment of this disease. Despite these accomplishments, a number of questions require further study, such as definition of pharmacodynamic correlations, effects on the hypothalamic-pituitary-adrenal and gonadal axis, and the nature of its most common dose-limiting toxicity, which is a syndrome of malaise and fatigue. Cancer 1995 ; 75 :1927-34.

Therapeutic drug monitoring in cancer management

Several anticancer drugs display characteristics that make them suitable candidates for therapeutic drug monitoring (TDM), including substantial pharmacokinetic variability and a narrow therapeutic index. However, concentration-effect relationships (pharmacodynamics) of most antineoplastic agents have not been well defined, thus limiting the widespread clinical application of TDM for cancer chemotherapy. Strategic incorporation of pharmacokinetic studies during phase I-III clinical trials should facilitate the identification of concentration-effect relationships and the definition of clinically useful levels of treatment intensity. We review representative clinical studies that have defined pharmacodynamic relationships for methotrexate, teniposide, etoposide, carboplatin, and mercaptopurine. Given that TDM has impacted positively on the clinical use of many drugs belonging to other therapeutic classes, and that pharmacodynamic correlations have been identified in several recent studies of anticancer drugs, we consider implementation of TDM a rational strategy for optimizing the use of selected antineoplastics.

Pharmacodynamics of prolonged oral etoposide in patients with advanced non-small-cell lung cancer.

This study was undertaken to investigate the pharmacodynamic relationship between etoposide drug levels on 21-day oral treatment courses and hematologic toxicities in patients with advanced non-small-cell lung cancer (NSCLC). Thirty-two patients with stage IIIB or IV NSCLC were treated with oral etoposide 50 mg/m2/d for 21 consecutive days in combination with cisplatin 100 mg/m2 on day 1. Treatment was repeated every 28 days for up to six courses. Patients had not received previous chemotherapy and had a performance status of 0 to 2. Patients were monitored weekly while on treatment for compliance with oral etoposide and toxicity, including complete blood cell counts, and a blood sample before the daily etoposide dose (drug trough levels). Etoposide concentrations were measured in the plasma by high-performance liquid chromatography (HPLC). Three patients achieved a complete response (CR) and 10 patients a partial response for an objective response rate of 41% (95% confidence interval, 24% to 58%). The median survival was 4 months (range, 1 to 23). Neutropenia was dose-limiting, and two patients died of neutropenic sepsis. Pharmacodynamic correlations for drug concentrations and hematologic toxicities were available for 27 patients and a total of 76 treatment courses, and correlations were significant for graded hematologic toxicity and nadir counts of leukocytes, neutrophils, hemoglobin, and platelets. The grade of infection (77 courses) was also related to drug levels. Using data from 27 initial courses, a pharmacodynamic model was developed to estimate the nadir leukocyte or neutrophil count (WBCn, ANCn) based on the pretreatment count (WBCp, ANCp) and the etoposide concentration (Ec) as follows: WBCn = 0.35 (1 + WBCp x e-1.12 x Ec) and ANCn = 0.32 (1 + ANCp x e-2.47 x Ec). Etoposide concentrations are related to the resulting hematologic toxicities. It is possible to predict nadir counts in the first course by a pharmacodynamic model. The above equations need to be validated prospectively and may be useful in future studies of prolonged oral etoposide.

Pharmacodynamics of three daily infusions of etoposide in patients with extensive-stage small-cell lung cancer.

The objectives of this study were to define the pharmacodynamics of etoposide and to develop potentially useful models (1) to estimate the plasma clearance using a limited number of samples and (2) to describe the relationship between clearance and the dose-limiting toxicity. A total of 17 patients with extensive-stage small-cell lung cancer were treated with 150 mg/m2 etoposide daily for 3 consecutive days and with 100 mg/m2 cisplatin on day 3 only. Both drugs were given intravenously over 1 h. Treatment was repeated every 21 days for up to six courses. All patients were newly diagnosed (no previous chemotherapy or irradiation) and had a performance status of 0-2. Six patients achieved a complete response as confirmed by repeat bronchoscopy and five patients showed a partial response, for an overall objective response rate of 65% (95% confidence interval, 38%-87%). The median survival was 8 months (range, 1-24+ months). The dose-limiting toxicity was neutropenia. Etoposide pharmacokinetics were measured during the first course and determinations were repeated during courses 3 or 4 and 6. Complete blood counts were obtained weekly. Correlations for etoposide clearance and hematologic toxicities were evaluated for 17 initial courses and for an overall number of 33 courses. Pharmacodynamic correlations were significant for graded hematologic toxicities, as well as nadirs of leukocytes, neutrophils, and platelets for the initial courses and for all courses. To reduce the requirement for numerous blood samples, a limited sampling model was developed to estimate the area under the concentration versus time curve (AUC) with the following equation: AUC = 15.45 + 3.86 x C2 + 7.10 x C4, where C2 and C4 represent the etoposide concentrations at 2 and 4 h, respectively. The total plasma clearance was calculated as the dose divided by the AUC; correlations with toxicity were better for clearance expressed in milliliters per minute than for that expressed in milliliters per minute per square meter of body surface area. The absolute neutrophil count at the nadir (ANCn) can be estimated by the following pharmacodynamic model, which is based on 33 courses: ANCn = -0.399 + 0.024 x Ecl, where Ecl represents the etoposide clearance expressed in milliliters per minute. Further studies are necessary to validate both models prospectively.

Pharmacokinetics of beta-methyldigoxin in healthy humans III: Pharmacodynamic correlations.

Significant decreases in left ventricular ejection time and heart rate were observed after the oral and intravenous administration of beta-methyldigoxin. The time course of this action correlated with the time course of beta-methyldigoxin and its active metabolite, digoxin, in their deepest pharmacokinetic compartments and not with their plasma levels. This pharmacodynamic activity peaked (decrease of 6.3% at 0.6 mg iv and 3.5% at 0.3 mg iv; decrease of 3.8% at 0.6 mg po and 4.5% at 0.3 mg po) at about 10 hr, concomitantly with the amounts of beta-methyldigoxin in its deepest compartment and showed a terminal half-life equivalent to the 41 hr for beta-methyldigoxin. The relative peak heights and area under the ejection time-time curves indicated a linear dose-response relationship on intravenous administration and an effect greater than that reported for larger amounts of digoxin. The time course of heart rate action correlated (8.3 and 12.5% decreases with 0.3 and 0.6 mg iv, respectively; 6.5 and 9.5% decreases with 0.3 and 0.6 mg po, respectively) with the time course of beta-methyldigoxin and its metabolite digoxin in shallower pharmacokinetic compartments (peaks at approximately 80 min intravenously and 135 min orally), and significant effects had disappeared by 10 hr after drug administration. This finding indicated that the biophases differ for ejection time and heart rate action. Mean arterial blood pressure could not be correlated with the time course of drug, although a small consistent decrease (4-8%) was observed from 22 to 72 hr after drug administration.