Toxicokinetics of Colchicine in Humans: Analysis of Tissue, Plasma and Urine Data in Ten Cases

1 A specific and sensitive radioimmunoassay was used to study the toxicokinetics of colchicine in seven cases of acute human poisoning. Post-mortem tissue concentrations of colchicine were measured in three further cases.

Depending on the time of patient admission, two disposition processes could be observed. The first, in three patients, admitted early, showed a bi-exponential plasma colchicine decrease, with distribution half-lives of 30, 45 and 90 min. The second, in four patients, admitted late, showed a mono-exponential decrease. Plasma terminal half-lives ranged from 10.6 to 31.7 h for both groups.

2 Pharmacokinetic analysis of urine colchicine data was performed for two patients. The fraction of unchanged colchicine excreted in urine was about 30%, renal clearance was about 131 h-1 and three-fold less than total body clearance (391 h-1). The apparent volume of distribution was 211 kg-1.

3 Post-mortem tissue analysis showed an ubiquitous colchicine distribution. Colchicine accumulated at high concentrations in the bone marrow (more than 600 ng g-1), testicle (400 ng g-1), spleen (250 ng g-1), kidney (200 ng g-1), lung (200 ng g-1) and heart (95 ng g -1); it was also found in the brain (125 ng g-1).

4 This toxicokinetic study shows that after massive ingestion, the disposition parameters and kinetics of colchicine are not markedly modified from those occuring in healthy volunteers. The absorption process was not delayed and the distribution and elimination half-lives were in the range known to occur with therapeutic doses.

Immunogenicity of a hexavalent combination vaccine in rhesus monkeys

Preclinical immunogenicity studies were conducted in rhesus monkeys to determine whether there is immune interference in the response to one or more components of a hexavalent vaccine (Hexavac) that contains antigens from Haemophilus influenzae (Hib), hepatitis B (HB), diphtheria (D), tetanus (T), acellular pertussis (aP) and inactivated polio virus (IPV). Antibody responses were measured following co-administration of the components at three separate anatomical sites or administration as a hexavalent combination in a single site. After three injections of the hexavalent vaccine, the peak antibody responses to each component of the vaccine were >100-fold above pre-immune titers and persisted at levels >10-fold above pre-immune titers at approximately 1 year. Immune interference was observed in the peak response to HB, D and pertussis toxin, but was not seen at later time points. The results indicate that the rhesus monkey model may be useful for pre-clinical evaluation of combination vaccines.

Typing of rabies virus isolates by DNA enzyme immunoassay

BACKGROUND

Alternatives to antigenic typing are needed for epidemiologic surveys of the rabies virus associated with translocated coyotes and foxes, especially in areas where a closely related rabies virus is transmitted by striped skunks.

OBJECTIVES

We developed and evaluated two enzyme based typing methods for rabies virus. The products of a reverse transcription-polymerase chain reaction (RT/PCR) of the nucleoprotein gene were hybridized to type specific probes and detected by enzyme assay after immobilization on microtiter plates.

STUDY DESIGN

We tested RT/PCR products of 27 rabies isolates by two different DNA enzyme immunoassays (DEIA) and evaluated the quality of the results from the corresponding nucleotide sequence of the samples.

RESULTS

Using a set of two probes, one of the DEIAs correctly identified 26/27 samples as variants of rabies virus associated with either skunks, foxes, or coyotes. The identity of one fox rabies sample was unresolved by this assay. The second DEIA correctly identified 24/27 samples as variants of rabies virus associated with either skunks, foxes, or coyotes. This assay did not resolve the identity of two fox rabies samples, and misidentified one fox rabies sample as a skunk rabies sample.

CONCLUSIONS

DEIA can be used for epidemiologic studies of variants of rabies virus associated with skunks, foxes, and coyotes. Both DEIA methods were effective when typing probes recognized changes at a minimum of two nucleotide positions between variants, but only one assay method was sufficiently stringent to detect a single base pair mismatch. The inherent mutability of RNA viruses must be considered when designing and evaluating typing methods.

Effect of antivenom on venom pharmacokinetics in experimentally envenomed rabbits: toward an optimization of antivenom therapy

Antivenomous immunotherapy is still used empirically. To improve the efficacy and safety of immunotherapy, we studied the effects of administering antivenom antibodies (F(ab')2) on the pharmacokinetics of the Vipera aspis venom in rabbits. Free venom levels were measured by enzyme-linked immunosorbent assay and total concentrations were quantified by measuring the radioactivity of trichloroacetic acid-precipitable radioiodinated venom. The intravenous infusion of 125 mg of antivenom 7 h after intramuscular injection with 700 microg x kg(-1) of V. aspis venom produced a redistribution of the venom antigens from the extravascular to the vascular space. Moreover, anti-venom antibodies were able to neutralize the totality of venom antigens in the vascular space, because no free plasma venom was detectable by enzyme-linked immunosorbent assay within 15 min after antivenom injection. Similar effects were obtained after injection of 25 mg of antivenom; however, the venom was only partially neutralized with lower doses (5 and 2.5 mg). We further established that intravenous injection is the most efficient route for antivenom administration, and we examined the effects of early and late immunotherapy. Finally, the efficacy of Fab antibodies was compared with that of F(ab')2; the plasma redistribution and the immunoneutralization of the venom were lower than those induced after injection of the same dose of F(ab')2. The difference between the effects of F(ab')2 and Fab could be explained by the differential pharmacokinetics of the two fragments.

Cyclosporin absorption is impaired by the fat substitutes, sucrose polyester and tricarballylate triester, in the rat

The effect of non-absorbable fat substitutes (sucrose polyester (SPE) and tricarballylate triester (TCTE)) on cyclosporin A (CsA) intestinal absorption was studied in the rat using in situ perfusion and gastric intubation techniques. A first experiment using the recirculating intestinal perfusion model showed that emulsions of either 5% SPE or TCTE significantly reduced (p < 0.0008) CsA absorption, whereas no difference was found between results for saline and 5% olive oil emulsion. In single-pass intestinal perfusion experiments SPE dose-dependently inhibited CsA absorption at SPE concentrations of 0.31% (p < 0.0004) and higher. Using gastric intubation, whole blood CsA concentrations significantly decreased when administered with SPE and TCTE in comparison with olive oil (p < 0.04). These results confirm that the CsA fraction dissolved in the undigested oil phase, constituted by the undigested and nonabsorbed fat substitute, is unavailable for intestinal absorption.

Binding of colchicine and thiocolchicoside to human serum proteins and blood cells

The binding of 3H-colchicine and its derivative 3H-thiocolchicoside to human serum, purified human proteins and blood cells was studied by equilibrium dialysis and centrifugation. Binding of colchicine and thiocolchicoside to human serum was 38.9 C +/- 4.7 and 12.8 C +/- 5.3%, respectively, essentially to albumin. Protein binding was not dependent on the concentration of either drug between 10(-10) and 10(-5)M. The binding of colchicine and thiocolchicoside to isolated erythrocytes (55 C +/- 5.6 and 16.5 C +/- 2.1%, respectively) decreased markedly in the presence of human serum proteins, i.e. in whole blood (38.7 C +/- 3.1 and 3.4 C +/- 0.8%). Binding of colchicine and thiocolchicoside to other blood cells was very low C < 3%). These binding properties in the blood compartment do not predispose colchicine and thiocolchicoside to be pharmacokinetically sensitive to binding displacement by drug interactions.

Radioimmunoassay of colchicine with antisera exhibiting variable cross-reactivity

Colchicine-specific antibodies were produced in either goats or rabbits immunized with three different colchicine haptens conjugated to bovine serum albumin (BSA) at different coupling sites on the three rings of colchicine. Antibodies exhibited a variable cross-reactivity for metabolites and structural analogs of colchicine, which were dependent on the site at which colchicine coupled to the protein carrier. Specificity was also checked on urine samples by separating metabolites using high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA) in tandem. The three antisera presented similar high-affinity constants for colchicine of the order of 10(10) M-1. A sensitive RIA for plasma colchicine was developed with each antiserum. The limit of detection of the three RIAs was 0.2 ng/ml. The inter- and intraassay coefficients were < 13%. RIA was linear up to 8 ng/ml. This RIA procedure was used to study the pharmacokinetics of a single dose of 1 mg oral colchicine in healthy volunteers and the colchicine concentrations of 27 plasma samples from patients on long-term colchicine treatment. No significant differences in plasma colchicine concentrations using the three assays were observed. This RIA procedure appears suitable for plasma colchicine pharmacokinetics and monitoring investigations.

Plasma kinetics and biliary excretion of colchicine in patients with chronic liver disease after oral administration of a single dose and after long-term treatment

Plasma kinetics and biliary excretion of colchicine in patients with chronic liver disease were evaluated after oral administration of a single dose and after long-term treatment. A single oral dose of 1 mg colchicine led to a mean peak concentration of 3.60 +/- 1.04 ng/ml at a peak time of 2.16 +/- 0.34 h and a mean area under the plasma concentration time curve, extrapolated from time 0 to infinity, of 24.90 +/- 8.47 ng.h/ml. Comparable values were obtained after repeated administration. Distribution half-life was 2.83 +/- 0.74 h, and terminal plasma half-life was 9.81 +/- 2.08 h; the mean apparent volume of distribution and the mean apparent plasma clearance were 1448 +/- 4061 and 175.3 +/- 47.6 1/h, respectively. Colchicine concentrations in bile (2025 +/- 1368 ng/ml) were clearly higher than in plasma. Long-term treatment with colchicine (1 mg/day) in patients with various stages of primary biliary cirrhosis (PBC) was associated with colchicine concentrations varying from < 0.15 to 2.0 ng/ml, with a slight tendency to higher concentrations in PBC stages III-IV than I-II. Although about 20% of colchicine is excreted in bile within 24 h, accumulation of colchicine may appear only in patients with advanced liver disease and cholestasis.

Pharmacokinetics of Vipera aspis venom after experimental envenomation in rabbits

Toxicokinetic studies of Vipera aspis venom were performed in rabbits after experimental envenomation. Venom proteins with a molecular weight greater than 6 kDa (high-molecular weight proteins) and which reacted in enzyme-linked immunosorbent assay with specific antiviper venom Fab'2, were also responsible for the lethal potency and the capillary permeability increasing activity of the venom. Conversely, low-molecular weight proteins were not detected by enzyme-linked immunosorbent assay and were pharmacologically inactive. The toxicokinetics of both classes of venom components were studied, using high-molecular weight and low-molecular weight radiolabeled proteins as well as enzyme-linked immunosorbent assay. After intravenous injection, Vipera aspis venom in plasma followed a biexponential decline with a distribution half-life of 0.7 hr and an elimination half-life of 12 hr. The distribution volume was 1.2 l.kg-1 and the systemic clearance was 84 ml.hr-1.kg-1. Venom levels in plasma after intramuscular injection of three doses (300, 500 and 700 micrograms/kg) of venom increased within the few hours after the venom administration to reach maximal values proportional to the injected doses. They subsequently followed a monoexponential decline, with an apparent terminal half-life of 32.5 hr. Absorption was a kinetically complex process, rapid during the first 24 hr and continued at a slower rate over the subsequent 72 hr. Bioavailability of venom was about 65%, regardless of the administered dose, and less than 5% of venom injected was excreted by the renal route.

Pharmacokinetics and absolute bioavailability of colchicine after i.v. and oral administration in healthy human volunteers and elderly subjects

The pharmacokinetics of colchicine were studied in six healthy male and four elderly female volunteers after i.v. and oral administration. Plasma samples were collected over 72 h and assayed for colchicine by a specific and sensitive radioimmunoassay. Plasma concentration-time curves were fitted using a three-compartmental model after i.v. administration of 0.5 mg (healthy volunteers) and 1 mg (elderly group) colchicine. The first distribution half-life (t1/2 lambda 1) was short: 9.2 min in healthy volunteers and 3.0 min in the elderly group; the second distribution half-life (t1/2 lambda 2) was of the same order for both groups, 1.2 h. Plasma elimination half-lives were also in the same range: 30 h for healthy volunteers versus 34 h for the elderly subjects. Mean residence time was also in the same range in the two groups: 27 h in healthy volunteers and 21 h for elderly subjects. The volume of distribution (Vz) was 6.7 l.kg-1 for the healthy group and 6.3 l.kg-1 for the elderly group, while Vss was smaller: 4.2 l.kg-1 for healthy volunteers and 2.9 l.kg-1 for elderly subjects. Total body clearance was 10.5 l.h-1 for healthy and 5.5 l.h-1 for elderly subjects. After oral administration of 1 mg, lag-time was 14 min in healthy volunteers and 11 min in elderly subjects. Maximal plasma concentration was 5.5 ng.ml-1 at 62 min in the healthy group, while in the elderly group Cmax was 12 ng.ml-1 at 87 min. Mean absolute bioavailability of the tablet was the same in both groups, 44% for healthy volunteers and 45% for elderly subjects.

[Immunotherapy of drug poisoning]

Immunotherapy of drug intoxications is based on intravenous administration of antibodies or antibody Fab fragments specific to a drug. Mechanism of action involves toxin complexation in the antibody distribution space resulting in a gradient efflux of the toxin from its binding site by dissociation of toxin-receptor to the vascular space. Reversal of toxic effects by specific Fab fragments has been demonstrated experimentally for digitalis, colchicine and tricyclic antidepressants. The intravenous administration of antibodies or Fab fragments alters toxin pharmacokinetics including tissular depletion, plasma redistribution and decrease of systemic clearance. Benefit of this therapy in clinical toxicology has been clearly shown for cardiac glycosides but has to be confirmed for colchicine and tricyclic antidepressants. Safety and efficacy of specific Fab fragments should permit an extension of this antidotal procedure towards other toxins.

Effect of colchicine-specific Fab fragments on the hepatic clearance of colchicine

The influence of colchicine-specific Fab fragments on hepatic metabolism and biliary excretion of colchicine was studied in the isolated perfused rat liver. Isolated rat livers were perfused for 180 min with either [3H]colchicine (initial concentration: 50 ng/ml) or Fab-[3H] colchicine in a stoichiometrical proportion at a constant flow of 100 ml/min in a recirculating system. Based on perfusate concentrations, the hepatic extraction ratio of colchicine was more than 15-fold decreased when colchicine was bound to Fab fragments (E = 0.011 +/- 0.001) than when it was infused alone (E = 0.16 +/- 0.01) (p < 0.01). The extensive binding of colchicine to Fab over the experimental period as demonstrated by equilibrium dialysis (97 +/- 2%) prevented hepatic uptake. At the end of the colchicine perfusion experiment, 74.2 +/- 4.9% of the radioactivity infused was excreted by the biliary route. In contrast, biliary excretion of radioactivity was 10-fold lower when [3H]colchicine was perfused complexed with Fab fragments (p < 0.01). However, the metabolic profile of colchicine was not affected by Fab fragments. The apparent half-life of colchicine metabolites calculated from biliary data was similar to that of colchicine, indicating that the biliary excretion of these metabolites was formation rate-limited. Inhibition of colchicine uptake by specific Fab fragment was confirmed in vitro with isolated hepatocytes.

Effect of fat substitutes, sucrose polyester and tricarballylate triester, on digitoxin absorption in the rat

The effect of non-absorbable fat substitutes (sucrose polyester (SPE) and tricarballylate triester (TCTE)) on [3H]digitoxin intestinal absorption was studied in the rat using a small intestine in-situ perfusion technique. The effect of SPE and TCTE was compared with that of sunflower oil, oleic acid, and saline. After 120 min perfusion, 5% SPE emulsion significantly reduced (P < 0.001) digitoxin absorption compared with all other treated groups. Five per cent TCTE emulsion had a less marked effect than SPE (P = 0.0002) and did not differ from sunflower oil. No difference was found between saline and 5% oleate emulsion, which did not reduce digitoxin absorption compared with other treated groups (P < 0.02). When taurocholic acid and lipase were added, results for the saline-, TCTE-, and SPE-treated groups were similar to those above, but the sunflower oil-treated group showed significantly enhanced (P < 0.01) digitoxin absorption. Thin-layer chromatography of the lipid phases showed hydrolysis of sunflower oil in the presence of taurocholic acid and lipase, but not of TCTE or SPE. The inhibitory effect of the non-absorbable fat substitutes on digitoxin absorption could be related to drug sequestration by the persistent oil phase constituted by the undigested and then unabsorbed fat substitutes. That part of digitoxin dissolved in the undigested oil phase is consequently unavailable for intestinal absorption.

Quantitation of venom antigens from European vipers in human serum or urine by ELISA

We describe an enzyme-linked immunosorbent assay (ELISA) to quantitate venom antigens in human serum and urine, and thus to help evaluate the severity of envenomation due to viper bites. This assay, which is performed with commercially available polyclonal Fab'2s in a double-sandwich method, is rapid, simple, and specific for antigens of European vipers (Vipera aspis, Vipera berus, and Vipera ammodytes). No cross-reactivity was observed with other snake venoms or human serum proteins. It showed a good linear response over a wide range of concentrations of venom antigens (from 1 to 100 ng/mL). It was very sensitive, with detection limits of 7 and 2 ng/mL for Vipera aspis venom in serum and urine, respectively. This ELISA is also easily reproducible; the coefficients of variation determined at different concentrations of venom (50, 25, and 5 ng/mL) did not exceed 10% in serum and 14% in urine samples collected from different donors. This test was applied to determine the concentrations of venom in the serum of patients bitten by a viper in France and to follow its elimination as a function of time. The method is adaptable to other venoms by using other specific immunoglobulins.

Uptake, 3-, and 6-glucuronidation of morphine in isolated cells from stomach, intestine, colon, and liver of the guinea pig

Orally administered morphine undergoes a considerable first-pass glucuronidation in animals and humans. However, the respective contribution of the gastrointestinal tract and the liver to the formation of the analgetically highly potent morphine-6-glucuronide (M6G) and the inactive morphine-3-glucuronide (M3G) is still debated. In this study, morphine uptake and biotransformation to M3G and M6G were compared in isolated cells from stomach, intestine, colon, and liver of the guinea pig. Morphine was taken up by all cell types in a time-dependent manner. There was evidence for a carrier-mediated accumulation in liver cells, but not in the other cell types. Morphine was glucuronidated to M3G by gastric, intestinal, colonic, and liver cells, and to M6G by all cell types excepted gastric cells. The M3G/M6G ratio averaged 3.5, 4.7, and 5.4 for colonic, intestinal, and liver cells, respectively. At low (1 microM) morphine concentration, glucuronidation rates for M3G and M6G in intestinal cells (88 and 20 pmol x mg protein-1 x hr-1, respectively) were similar to those in liver cells (133 and 12 pmol x mg protein-1 x hr-1, respectively). At high concentration (100 microM), rates of M3G and M6G formation in liver cells exceeded by 5- to 10-fold those of intestinal or colonic cells. In conclusion, the epithelium of the small and large intestine contributes with the liver to the formation of the active M6G; at the same time, the gastric, intestinal, and colonic epithelia are involved in the inactivation of morphine to M3G.

Pharmacokinetics of colchicine: a review of experimental and clinical data

Thanks to the development of a sensitive and specific radioimmunoassay for colchicine, the pharmacokinetics of colchicine is now well-established after single oral doses. Absorption is characterized by a zero-order rate constant while disposition appears biexponential with a rapid distribution phase (t1/2 = 1.8 h) and a long elimination phase (t1/2 = 20 h). All studies confirm the large total body clearance (35 l/h) predominantly by the extrarenal route and the large distribution volume (700 l). Further studies need to be performed to investigate colchicine absorption and to describe the metabolic pathway of the drug. To date, relationships between colchicine plasma levels and pharmacological effects have not been defined. Monitoring of plasma levels in patients with familial Mediterranean fever should improve treatment with colchicine. However, the therapeutic range has not been precisely determined. The use of colchicine in the treatment of liver cirrhosis and primary biliary cirrhosis is a recent development; so, assuming that a large part of total body clearance depends on hepatic function, the influence of hepatic diseases on colchicine disposition needs to be investigated in order to define the most appropriate therapeutic dosing.

Reversal of murine colchicine toxicity by colchicine-specific Fab fragments

High-affinity Fab fragments (2 x 10(10) M-1) specific to colchicine were produced to evaluate their potency in reversing murine colchicine intoxication. Intraperitoneal injection of a 4.46 mg/kg colchicine dose was lethal for 100% of mice. 1.5 h after colchicine administration, a group of 10 mice was treated with colchicine-specific Fab fragments at a half-stoichiometrical dose compared to the colchicine dose by intravenous and intraperitoneal routes. 70% of the Fab-infused mice survived (P less than 0.01). This high efficiency of colchicine-specific Fab fragments in reversing acute murine colchicine toxicity suggests that Fab fragments would be an efficient antidote for the treatment of human colchicine poisoning.

Relationship between red blood cell potassium and plasma digitoxin concentrations in intoxicated patients

After severe acute self-poisoning by cardiac glycosides, significant and persistent depletion of red blood cell K+ due to inhibition of Na+K+ ATPase is seen. Because of a delay between the time course of plasma digitalis concentrations and that of red blood cell K+ depletion, no direct relation exists between the two, and RBC K+ has hitherto not been considered useful as prognostic indicators of clinical outcome. In an effort to solve this problem, red blood cell K+ was measured by atomic absorption spectrophotometry and plasma digitoxin concentration assayed in six patients admitted to an intensive care unit after digitoxin self-poisoning. Using the effect compartment model of Sheiner, a relationship based on a sigmoid Emax model was able to relate the digitoxin concentration at the action site to red blood cell K+ depletion. Thus the duration of red blood cell K+ depletion could be predicted from two relative simple in vitro assays. Since RBC K+ is a marker of the inhibition of Na+K+ ATPase by digitoxin, this method could be of use for the management of patients self-poisoned with digitalis.

Dose-dependent reversal of acute murine colchicine poisoning by goat colchicine-specific Fab fragments

The use of colchicine-specific Fab fragments is of interest in human poisoning. In the present study, we show the efficacy of Fab fragments in reversing colchicine toxicity in mice. High affinity antibodies (Ka = 2 x 10(10) M-1) against colchicine were raised in goats; Fab fragments were purified by DEAE chromatography after papain hydrolysis of IgG. Mice were intoxicated with a 100% lethal colchicine dose (3.8 mg/kg). When a half molar dose (M/2) of Fab fragments in relation to the colchicine dose was intravenously and intraperitoneally administered 90 min after colchicine infusion using a multiple dosage schedule, 80% of the Fab-treated mice survived compared to the control group which did not receive Fab fragments (P less than 0.01). Using a M/4 and M/8 dose of Fab fragments, the mortality was respectively 50% and 80%. The dose-effect relationship was linear (r = 0.99). Delayed administration of a M/2 dose of Fab fragments 6 h after colchicine administration resulted in 50% survival (P less than 0.01). Body temperature and body weight were selective markers of the severity of the intoxication. In the control group, a marked decrease of body temperature was observed following the first few hours after the intoxication (-21% compared to basal value 48 h after colchicine). In the Fab-treated group, the decrease was inversely related to the Fab fragment dose. Body temperature returned to the basal values 7 days after intoxication. A progressive decrease in body weight was concomitantly observed in intoxicated mice until death, while values returned to baseline 9 days after colchicine in surviving Fab-treated mice.

The effect of nortriptyline-specific active immunization on amitriptyline toxicity and disposition in the rabbit

Rabbits were actively immunized by a conjugate of nortriptyline (NT) to study the effect of specific anti-NT antibodies on toxicity and disposition of amitriptyline (AT). Control and immunized rabbits received 115 mg/kg AT intraperitoneally (i.p.). The lethality dose (LD) profile exhibited a gentle slope; LD100 and LD0 were separated by 100 mg/kg. Mortality was significantly reduced from LD67 to LD43 (P less than 0.05). Total plasma concentrations of the toxin were increased in the immunized group compared to the control group. AUC0.5-24 h value was 5-fold higher in the immunized group than in the control group. Moreover, a smaller fraction of unbound toxin in plasma was observed in the immunized group than in the control group. These observations indicate that AT was actively sequestered by antibodies. The intensity of this phenomenon was a function of both the antibody affinity constant (10(9) M-1) and the neutralizing capacity (varying from 0.005 to 0.2 mg/kg) of the circulating antibodies in each immunized rabbit. Results clearly show that anti-NT antibodies are able to effectively sequestrate AT.

Specific anti-digoxin Fab fragments: an available antidote for proscillaridin and scilliroside poisoning?

The purpose of this study was to evaluate the capacity of specific anti-digoxin Fab fragments to bind to and neutralize scilliroside and proscillaridin in acute poisoning. Apparent affinity constants were determined with values of 2.6 10(8)M-1 for scilliroside and 3.8 10(7)M-1 for proscillaridin. These results are in accordance with a possible in-vivo neutralization of these toxins.