artelinic-acid and artemotil

Studies with laboratory animals have demonstrated fatal neurotoxicity that is associated with administration of artemether (AM) and arteether (AE) intramuscularly or artelinic acid (AL) orally. Toxicokinetic studies showed oil-soluble artemisinins form a depot at the intramuscular injection sites, which is associated with fascia inflammation in muscles. Oral administration of AL induces a gastrointestinal toxicity that is linked with delayed gastric emptying. These effects suggest that the exposure time of artemisinins was extended due to drug accumulation in blood, and this in turn resulted in neurotoxicity. In the present report, the drug exposure time with a neurotoxic outcome (neurotoxic exposure time) was evaluated as a predictor of neurotoxicity in vivo. The neurotoxic exposure time represents a total time spent above a lowest observed neurotoxic effect levels (LONEL) in plasma. The dose of AE required to induce minimal neurotoxicity requires a 2-3 fold longer exposure time in rhesus monkeys (179.5 h) than in rats (67.1 h) and dogs (103.7 h) by using a daily dose of 6-12.5 mg/kg for 7-28 days, indicating that the safe dosing duration in monkeys should be longer than 7 days under the exposure. The neurotoxic exposure time of artemisinins could be longer in humans as the comparison of monkeys to humans is likely more relevant than from rodents or dogs. Oral AL required much longer exposure times (8-fold) than intramuscular AE to induce neurotoxicity, suggesting that water-soluble artemisinins appear to be much safer than oil-soluble artemisinins. Due to lower doses (2-4 mg/kg) used with current artemisinins and the more rare use of AE in treating humans the exposure time is much shorter in humans. Therefore, the current regimen of 3-5 days dosing duration should be quite safe. These findings support a recently published WHO guide for malaria treatment with artemisinin regimens, such as artemisinin-based combination therapies and injectable artesunate, to avoid neurotoxicity.

Topics: Animals; Antimalarials; Artemether; Artemisinins; Dose-Response Relationship, Drug; Drug Administration Schedule; Humans; Neurotoxicity Syndromes; No-Observed-Adverse-Effect Level; Species Specificity

An economical phase-transfer method is used to prepare 10-arylaminoartemisinins from DHA and arylamines, and artemether, arteether, and artelinate from the corresponding alcohols. In vivo sc screens against Plasmodium berghei and P. yoelii in mice reveal that the p-fluorophenylamino derivative 5 g is some 13 and 70 times, respectively, more active than artesunate; this reflects the very high sc activity of 10-alkylaminoartemisinins. However, through the po route, the compounds are less active than the alkylaminoartemisinins, but still approximately equipotent with artesunate.

Topics: Animals; Antimalarials; Artemether; Artemisinins; Malaria; Mice; Molecular Structure; Parasitemia; Plasmodium berghei; Plasmodium falciparum; Plasmodium yoelii; Sesquiterpenes

Three artemisinin antimalarials, arteether (AE), artesunate (AS), and artelinate (AL) were evaluated in rats using an auditory discrimination task (ADT) and neurohistology. After rats were trained on the ADT, equimolar doses of AE (25 mg/kg, in sesame oil, n=6), AS (31 mg/kg, in sodium carbonate, n=6), and AL (36 mg/kg, in saline, n=6), or vehicle (sodium carbonate, n=6) were administered (IM) for 7 consecutive days. Behavioral performance was evaluated, during daily sessions, before, during, and after administration. Histological evaluation of the brains was performed using thionine staining, and damaged cells were counted in specific brainstem nuclei of all rats. Behavioral performance was not significantly affected in any rats treated with AS, AL, or vehicle. Furthermore, histological examination of the brains of rats treated with AS, AL, and vehicle did not show damage. In stark contrast, all rats treated with AE showed a progressive and severe decline in performance on the ADT. The deficit was characterized by decreases in accuracy, increases in response time and, eventually, response suppression. When performance on the ADT was suppressed, rats also showed gross behavioral signs of toxicity that included tremor, gait disturbances, and lethargy. Subsequent histological assessment of AE-treated rats revealed marked damage in the brainstem nuclei, ruber, superior olive, trapezoideus, and inferior vestibular. The damage included chromatolysis, necrosis, and gliosis. These results demonstrate distinct differences in the ability of artemisinins to produce neurotoxicity. Further research is needed to uncover pharmacokinetic and metabolic differences in artemisinins that may predict neurotoxic potential.

Topics: Animals; Antimalarials; Artemisinins; Artesunate; Behavior, Animal; Brain; Brain Stem; Discrimination Learning; Male; Rats; Rats, Sprague-Dawley; Sesquiterpenes

The pharmacokinetics and bioavailability of dihydroartemisinin (DQHS), artemether (AM), arteether (AE), artesunic acid (AS) and artelinic acid (AL) have been investigated in rats after single intravenous, intramuscular and intragastric doses of 10 mg kg(-1). Plasma was separated from blood samples collected at different times after dosing and analysed for parent drug. Plasma samples from rats dosed with AM, AE, AS and AL were also analysed for DQHS which is known to be an active metabolite of these compounds. Plasma levels of all parent compounds decreased biexponentially and were a reasonable fit to a two-compartment open model. The resulting pharmacokinetic parameter estimates were substantially different not only between drugs but also between routes of administration for the same drug. After intravenous injection the highest plasma level was obtained with AL, followed by DQHS, AM, AE and AS. This resulted in the lowest steady-state volume of distribution (0.39 L) for AL, increasing thereafter for DQHS (0.50 L), AM (0.67 L), AE (0.72 L) and AS (0.87 L). Clearance of AL (21-41 mL min(-1) kg(-1)) was slower than that of the other drugs for all three routes of administration (DQHS, 55-64 mL min(-1) kg(-1); AM, 91-92 mL min(-1) kg(-1); AS, 191-240 mL min(-1) kg(-1); AE, 200-323 mL min(-1) kg(-1)). In addition the terminal half-life after intravenous dosing was longest for AL (1.35 h), followed by DQHS (0.95 h), AM (0.53 h), AE (0.45 h) and AS (0.35 h). Bioavailability after intramuscular injection was highest for AS (105%), followed by AL (95%) and DQHS (85%). The low bioavailability of AM (54%) and AE (34%) is probably the result of slow, prolonged absorption of the sesame-oil formulation from the injection site. After oral administration, low bioavailability (19-35%) was observed for all five drugs. In-vivo AM, AE, AS and AL were converted to DQHS to different extents; the ranking order of percentage of total dose converted to DQHS was AS (25.3-72.7), then AE (3.4-15.9), AM (3.7-12.4) and AL (1.0-4.3). The same ranking order was obtained for all formulations and routes of administration. The drug with the highest percentage conversion to DQHS was artesunic acid. Because DQHS has significant antimalarial activity, relatively low DQHS production could still contribute significantly to the antimalarial efficacy of these drugs. This is the first time the pharmacokinetics, bioavailability and conversion to DQHS of these drugs have been directly compared after

Topics: Absorption; Animals; Antimalarials; Area Under Curve; Artemether; Artemisinins; Biological Availability; Bridged Bicyclo Compounds, Heterocyclic; Male; Rats; Rats, Sprague-Dawley; Sesquiterpenes; Succinates

The in vitro activities of chloroquine, quinine, mefloquine, halofantrine, artemisinin, arteether, artemether, and artelinate were evaluated against African clones and isolates of Plasmodium falciparum, using an isotopic, semimicro, drug susceptibility test. The chloroquine-resistant FCM 29 clone was 1.6 and 6.2 times more susceptible to artemisinin when compared with the chloroquine-susceptible, mefloquine-, and halofantrine-resistant L-3 and L-16 clones, respectively. Cross-resistance patterns between the standard antimalarial drugs and artemisinin were determined against 36 African isolates of P. falciparum obtained from imported cases of malaria in France. Chloroquine-resistant isolates (n = 21) were significantly more susceptible to artemisinin (50% inhibitory concentration [IC50] 7.67 nM), arteether (IC50 3.88 nM), artemether (IC50 3.71 nM), and artelinate (IC50 3.46 nM), as compared with the 15 chloroquine-susceptible isolates (IC50 11.4, 5.66, 5.14, and 5.04 nM, respectively). Arteether, artemether, and artelinate were equally effective and twice as potent as artemisinin. A significant positive correlation was found between artemisinin and mefloquine (r = 0.424, P = 0.022), artemisinin and halofantrine (r = 0.569, P < 0.001), chloroquine and quinine (r = 0.651, P < 0.001), and mefloquine and halofantrine (r = 0.863, P < 0.001), suggesting in vitro cross-resistance among these drugs. The present in vitro findings require confirmation in clinical studies.

Topics: Animals; Antimalarials; Artemether; Artemisinins; Chloroquine; Drug Resistance; Mefloquine; Phenanthrenes; Plasmodium falciparum; Quinine; Sesquiterpenes

1. In this communication, induction of hydrogen peroxide production by the semisynthetic antimalarial drugs of the artemisinin class (beta-arteether, beta-artelinic acid and dihydroartemisinin) in rat liver microsomes, is reported. 2. Endogenous, NADPH-dependent, production of hydrogen peroxide in rat liver microsomes was enhanced in the presence of arteether and artelinic acid, but not in the presence of dihydroartemisinin. 3. NADPH-dependent metabolism of arteether and artelinic acid was closely coupled to the drug-induced production of hydrogen peroxide. 4. The redox cycle of cytochrome P-450 was presented, which describes satisfactorily both the endogenous and the drug-assisted hydrogen peroxide production in rat liver microsomes; also, the rate-limiting step of the cycle was identified.

Topics: Animals; Antimalarials; Artemisinins; Hydrogen Peroxide; Kinetics; Male; Microsomes, Liver; NADP; Rats; Rats, Inbred Strains; Sesquiterpenes

1. In this communication, metabolism of the semisynthetic antimalarial drugs of the artemisinin class (beta-arteether, beta-artelinic acid and dihydroartemisinin) in rat liver microsomes, is reported. 2. Dihydroartemisinin was the major early metabolite of arteether (57%) and artelinic acid (80%); in addition, arteether was hydroxylated in the positions 9 alpha- and 2 alpha- of the molecule. 3. Dihydroartemisinin was further metabolized by extensive hydroxylation of its molecule; we were able to identify four hydroxylated derivatives of DQHS, but not the exact positions of the hydroxyl groups. 4. The rates of NADPH-supported metabolism of arteether, artelinic acid and dihydroartemisinin in rat liver microsomes were: 4.0, 2.5 and 1.3 nmol/min/mg of microsomal protein, respectively. 5. The apparent affinity constants of arteether and artelinic acid for the microsomal metabolizing system, calculated from the rates of product formation, were 0.54 mM and 0.33 mM (for arteether) and 0.11 mM (for artelinic acid), respectively. The appearance of two affinity constants indicated that arteether was metabolized by two different isoenzymes of cytochrome P-450 in rat liver microsomes.

Topics: Animals; Antimalarials; Artemisinins; Chromatography, High Pressure Liquid; Chromatography, Liquid; Kinetics; Liver; Male; Mass Spectrometry; Microsomes, Liver; Rats; Rats, Inbred Strains; Sesquiterpenes