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Edstein MD, Kocisko DA, Walsh DS, Eamsila C, Charles BG, Rieckmann KH. Plasma concentrations of tafenoquine, a new long-acting antimalarial agent, in thai soldiers receiving monthly prophylaxis. Clin Infect Dis 2003; 37:1654-8. [PMID: 14689348 DOI: 10.1086/379718] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2003] [Accepted: 08/06/2003] [Indexed: 11/03/2022] Open
Abstract
We measured plasma tafenoquine concentrations in Thai soldiers given a monthly regimen of tafenoquine to determine whether these concentrations adequately suppressed malarial infections on the Thai-Cambodian border. After receiving a treatment course of artesunate and doxycycline, 104 male soldiers were administered a loading dose of tafenoquine (400 mg daily for 3 days), followed by tafenoquine monthly (400 mg every 4 weeks) for 5 months. Consecutive monthly mean (+/- standard deviation) trough plasma tafenoquine concentrations were 223+/-41, 127+/-29, 157+/-51, 120+/-24, and 88+/-20 ng/mL. Only 1 soldier developed malaria during the study. At the time of malaria diagnosis, his plasma tafenoquine concentration was 40 ng/mL, which was approximately 3-fold lower than the trough concentrations of the other soldiers. Although low tafenoquine concentrations appear to be uncommon, additional investigations are needed to determine the relationship between plasma tafenoquine concentrations and suppression of malaria.
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52
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McGready R, Stepniewska K, Edstein MD, Cho T, Gilveray G, Looareesuwan S, White NJ, Nosten F. The pharmacokinetics of atovaquone and proguanil in pregnant women with acute falciparum malaria. Eur J Clin Pharmacol 2003; 59:545-52. [PMID: 12955371 DOI: 10.1007/s00228-003-0652-9] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2003] [Accepted: 07/07/2003] [Indexed: 10/26/2022]
Abstract
OBJECTIVE To determine the pharmacokinetic properties of atovaquone, proguanil, and the triazine metabolite cycloguanil in women with recrudescent multi-drug resistant falciparum malaria during the second and third trimesters of pregnancy treated by artesunate-atovaquone-proguanil. METHODS Serial plasma concentrations of atovaquone, proguanil and cycloguanil were measured in 24 women at baseline and after the final dose of the 3-day treatment with atovaquone (20 mg/kg/day) plus proguanil (8 mg/kg/day) plus artesunate (4 mg/kg/day) daily. RESULTS The triple combination was well tolerated and highly effective. The outcomes of pregnancy were all normal. Population mean (+/- SEM) oral clearance (Cl/F) estimates were 313+/-33 ml/h/kg and 1109+/-43 ml/h/kg, total apparent volume of distribution (Vd/F) 13.0+/-1.3 l/kg and 22.9+/-1.4 l/kg, and terminal elimination half-life; 29.1 h and 14.3 h, for atovaquone and proguanil, respectively. Using conventional and population pharmacokinetic analyses, Cl/F and Vd/F estimates for both drugs were approximately twice, and plasma concentrations less than half those reported previously in healthy subjects and patients with acute malaria. CONCLUSION Artesunate-atovaquone-proguanil is a promising treatment for multi-drug resistant falciparum malaria during pregnancy, but the dose of atovaquone-proguanil may need to be increased.
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MESH Headings
- Acute Disease
- Antimalarials/administration & dosage
- Antimalarials/blood
- Antimalarials/pharmacokinetics
- Antimalarials/therapeutic use
- Artemisinins/administration & dosage
- Artemisinins/blood
- Artemisinins/pharmacokinetics
- Artemisinins/therapeutic use
- Artesunate
- Atovaquone
- Drug Combinations
- Drug Resistance, Multiple
- Drug Therapy, Combination
- Female
- Humans
- Malaria, Falciparum/blood
- Malaria, Falciparum/drug therapy
- Malaria, Falciparum/metabolism
- Naphthoquinones/administration & dosage
- Naphthoquinones/blood
- Naphthoquinones/pharmacokinetics
- Naphthoquinones/therapeutic use
- Pregnancy
- Pregnancy Complications, Parasitic/blood
- Pregnancy Complications, Parasitic/drug therapy
- Pregnancy Complications, Parasitic/metabolism
- Pregnancy Outcome
- Pregnancy Trimester, Second
- Pregnancy Trimester, Third
- Proguanil/administration & dosage
- Proguanil/blood
- Proguanil/pharmacokinetics
- Proguanil/therapeutic use
- Sesquiterpenes/administration & dosage
- Sesquiterpenes/blood
- Sesquiterpenes/pharmacokinetics
- Sesquiterpenes/therapeutic use
- Thailand
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Affiliation(s)
- R McGready
- Shoklo Malaria Research Unit, PO Box 46, Mae Sot, Thailand
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53
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McKeage K, Scott L. Atovaquone/proguanil: a review of its use for the prophylaxis of Plasmodium falciparum malaria. Drugs 2003; 63:597-623. [PMID: 12656656 DOI: 10.2165/00003495-200363060-00006] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
UNLABELLED Atovaquone/proguanil is a fixed-dose combination tablet of two antimalarial agents and is highly effective for the prevention of Plasmodium falciparum malaria. In combination with proguanil, the ability of atovaquone to inhibit parasitic mitochondrial electron transport is markedly enhanced. Both atovaquone and proguanil are active against hepatic (pre-erythrocytic) stages of P. falciparum, thereby providing causal prophylaxis and eliminating the need to continue post-travel treatment beyond 7 days. Both agents are also active against erythrocytic stages of P. falciparum, thereby providing suppressive prophylaxis. Atovaquone/proguanil is highly effective against drug-resistant strains of P. falciparum, and cross-resistance has not been observed between atovaquone and other antimalarial agents. In comparative, randomised clinical trials, there were no cases of P. falciparum malaria in nonimmune adults, adolescents and children (>/=11 kg) visiting malaria-endemic regions for </=28 days and receiving atovaquone/proguanil (250/100 mg in adults and dosage based on bodyweight in children <40 kg) once daily. The efficacy for the prevention of P. falciparum malaria was estimated at 100% for atovaquone/proguanil and for mefloquine, and 70% for chloroquine plus proguanil. In individuals (>/=11 kg) from endemic regions who may carry some immunity to malaria (semi-immune), the prophylactic efficacy rating for atovaquone/proguanil based on placebo-controlled trials was 95-100%. Atovaquone/proguanil is generally well tolerated by both adults and children. The most common treatment-related adverse events in placebo-controlled trials were headache and abdominal pain, which occurred at a rate similar to that observed with placebo. Atovaquone/proguanil therapy was associated with significantly fewer gastrointestinal adverse events than chloroquine plus proguanil, and significantly fewer neuropsychiatric adverse events than mefloquine in nonimmune individuals. Significantly fewer recipients of atovaquone/proguanil discontinued treatment because of adverse events than individuals receiving chloroquine plus proguanil or mefloquine (p < 0.05). CONCLUSION Atovaquone/proguanil is a fixed-dose combination antimalarial tablet that provides effective prophylaxis of P. falciparum malaria, including drug-resistant strains. Both atovaquone and proguanil are effective against hepatic stages of P. falciparum, which means that treatment need only continue for 7 days after leaving a malaria-endemic region. Atovaquone/proguanil was generally well tolerated and was associated with fewer gastrointestinal adverse events than chloroquine plus proguanil, and fewer neuropsychiatric adverse events than mefloquine. Thus, atovaquone/proguanil provides effective prophylaxis of P. falciparum malaria and compared with other commonly used antimalarial agents has an improved tolerability profile, and, overall, a more convenient dosage regimen, particularly in the post-travel period.
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Affiliation(s)
- Kate McKeage
- Adis International Limited, Auckland, New Zealand.
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54
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Yasui-Furukori N, Kondo T, Takahata T, Mihara K, Ono S, Kaneko S, Tateishi T. Effect of dietary fat content in meals on pharmacokinetics of quazepam. J Clin Pharmacol 2002; 42:1335-40. [PMID: 12463728 DOI: 10.1177/0091270002042012004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dietary fat content in meals has been reported to increase the absorption of several drugs proportionately. However, there is no information about the effects of dietary fat in meals on the sedative hypnotic agent quazepam, although limited data suggest that food intake alters quazepam absorption. Therefore, the authors measured and compared pharmacokinetic parameters of quazepam taken in a fasted state and taken 30 minutes after consuming meals containing different amounts of dietary fat. A three-arm randomized crossover study was conducted. Nine healthy male volunteers took a single oral 20-mg dose of quazepam under the following conditions: (1) after fasting overnight for at least 12 hours, (2) 30 minutes after consuming a low-fat meal (two slices of bread and 200 ml of apple juice), or (3) 30 minutes after consuming high-fat meal (two slices of bread with 30 gm of butter and 200 ml of apple juice). Plasma concentrations of quazepam and its metabolite, 2-oxoquazepam, were monitored up to 48 hours after the dosing. In comparison with corresponding plasma values for quazepam taken in a fasting state, the peak concentrations (Cmax) of quazepam taken 30 minutes after consuming a low-fat meal and high-fat meal were 243% (90% confidence interval [CI] = 161%-325%) and 272% (90% CI = 190%-355%), respectively. Area under the plasma concentration-time curve from 0 to 8 hours (AUC(0-8)) and 0 to 48 hours (AUC(0-48)) of quazepam was increased with the low-fat meal by 2-fold (90% CI = 1.5- to 2.7-fold) and 1.4-fold (90% CI = 1.0- to 1.7-fold), respectively, and with the high-fat meal by 2.2-fold (90% CI = 1.3- to 3-fold) and 1.5-fold (90% CI = 0.7- to 2.4-fold), respectively. The pharmacokinetic change in 2-oxoquazepam to the parent compound was similar. Quazepam was well tolerated, with no significant difference in the Stanford Sleepiness Scale between fasted and fed conditions. These findings show that food intake has an evident effect on quazepam absorption, but further studies are needed to clarify a determinant factor of this alteration (2.5-fold for Cmax and 2.1-fold for AUC(0-8), on average). It might not be necessary to do dose adjustment with meal content because quazepam is well tolerated.
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Affiliation(s)
- Norio Yasui-Furukori
- Department of Clinical Pharmacology, Hirosaki University School of Medicine, Hirosaki, Japan
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55
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Abstract
Interactions between food and drugs may inadvertently reduce or increase the drug effect. The majority of clinically relevant food-drug interactions are caused by food-induced changes in the bioavailability of the drug. Since the bioavailability and clinical effect of most drugs are correlated, the bioavailability is an important pharmacokinetic effect parameter. However, in order to evaluate the clinical relevance of a food-drug interaction, the impact of food intake on the clinical effect of the drug has to be quantified as well. As a result of quality review in healthcare systems, healthcare providers are increasingly required to develop methods for identifying and preventing adverse food-drug interactions. In this review of original literature, we have tried to provide both pharmacokinetic and clinical effect parameters of clinically relevant food-drug interactions. The most important interactions are those associated with a high risk of treatment failure arising from a significantly reduced bioavailability in the fed state. Such interactions are frequently caused by chelation with components in food (as occurs with alendronic acid, clodronic acid, didanosine, etidronic acid, penicillamine and tetracycline) or dairy products (ciprofloxacin and norfloxacin), or by other direct interactions between the drug and certain food components (avitriptan, indinavir, itraconazole solution, levodopa, melphalan, mercaptopurine and perindopril). In addition, the physiological response to food intake, in particular gastric acid secretion, may reduce the bioavailability of certain drugs (ampicillin, azithromycin capsules, didanosine, erythromycin stearate or enteric coated, and isoniazid). For other drugs, concomitant food intake may result in an increase in drug bioavailability either because of a food-induced increase in drug solubility (albendazole, atovaquone, griseofulvin, isotretinoin, lovastatin, mefloquine, saquinavir and tacrolimus) or because of the secretion of gastric acid (itraconazole capsules) or bile (griseofulvin and halofantrine) in response to food intake. For most drugs, such an increase results in a desired increase in drug effect, but in others it may result in serious toxicity (halofantrine).
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Affiliation(s)
- Lars E Schmidt
- Department of Clinical Pharmacology Q.7642, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark
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56
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Affiliation(s)
- Aaron L Baggish
- University of Connecticut School of Medicine, Farmington, Connecticut, USA
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57
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Cotreau MM, Stonis L, Dykstra KH, Gandhi T, Gutierrez M, Xu J, Park Y, Burghart PH, Schwertschlag US. Multiple-dose, safety, pharmacokinetics, and pharmacodynamics of a new selective estrogen receptor modulator, ERA-923, in healthy postmenopausal women. J Clin Pharmacol 2002; 42:157-65. [PMID: 11831538 DOI: 10.1177/00912700222011193] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
ERA-923 is a new selective estrogen receptor modulator under clinical investigation for use in tamoxifen refractory metastatic breast cancer. This study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of once-daily oral ERA-923 (10-200 mg) for 28 days in healthy postmenopausal females. ERA-923 was well tolerated, and adverse events were mild and reversible. No clinically significant changes in laboratory values were found with ERA-923 versus placebo. ERA-923 appeared to undergo extensive metabolism and enterohepatic recirculation. In addition, pharmacokinetic analysis showed that a high-fat breakfast increased the extent of absorption. ERA-923-dosed subjects had no uterine or ovarian changes when evaluated with transvaginal ultrasound and compared to placebo subjects. Overall, ERA-923 was safe and well tolerated in postmenopausal women dosed for 28 days.
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Affiliation(s)
- Monette M Cotreau
- Clinical Research and Development , Wyeth-Ayerst Research, Cambridge, Massachusetts, USA
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58
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McGready R, Cho T, Keo NK, Thwai KL, Villegas L, Looareesuwan S, White NJ, Nosten F. Artemisinin antimalarials in pregnancy: a prospective treatment study of 539 episodes of multidrug-resistant Plasmodium falciparum. Clin Infect Dis 2001; 33:2009-16. [PMID: 11712093 DOI: 10.1086/324349] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2001] [Revised: 07/12/2001] [Indexed: 11/03/2022] Open
Abstract
The emergence and spread of multidrug-resistant Plasmodium falciparum compromises the treatment of malaria, especially during pregnancy, where the choice of antimalarials is already limited. Artesunate (n=528) or artemether (n=11) was used to treat 539 episodes of acute P. falciparum malaria in 461 pregnant women, including 44 first-trimester episodes. Most patients (310 [57.5%]) received re-treatments after earlier treatment with quinine or mefloquine. By use of survival analysis, the cumulative artemisinin failure rate for primary infections was 6.6% (95% confidence interval, 1.0-12.3), compared with the re-treatment failure rate of 21.7% (95% confidence interval, 15.4-28.0; P=.004). The artemisinins were well tolerated with no evidence of adverse effects. Birth outcomes did not differ significantly to community rates for abortion, stillbirth, congenital abnormality, and mean gestation at delivery. These results are reassuring, but further information about the safety of these valuable antimalarials in pregnancy is needed.
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Affiliation(s)
- R McGready
- Shoklo Malaria Research Unit, Mae Sot, Mahidol University, Bangkok, Thailand
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59
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Schöler N, Krause K, Kayser O, Müller RH, Borner K, Hahn H, Liesenfeld O. Atovaquone nanosuspensions show excellent therapeutic effect in a new murine model of reactivated toxoplasmosis. Antimicrob Agents Chemother 2001; 45:1771-9. [PMID: 11353624 PMCID: PMC90544 DOI: 10.1128/aac.45.6.1771-1779.2001] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Immunocompromised patients are at risk of developing toxoplasma encephalitis (TE). Standard therapy regimens (including sulfadiazine plus pyrimethamine) are hampered by severe side effects. While atovaquone has potent in vitro activity against Toxoplasma gondii, it is poorly absorbed after oral administration and shows poor therapeutic efficacy against TE. To overcome the low absorption of atovaquone, we prepared atovaquone nanosuspensions (ANSs) for intravenous (i.v.) administration. At concentrations higher than 1.0 microg/ml, ANS did not exert cytotoxicity and was as effective as free atovaquone (i.e., atovaquone suspended in medium) against T. gondii in freshly isolated peritoneal macrophages. In a new murine model of TE that closely mimics reactivated toxoplasmosis in immunocompromised hosts, using mice with a targeted mutation in the gene encoding the interferon consensus sequence binding protein, i.v.-administered ANS doses of 10.0 mg/kg of body weight protected the animals against development of TE and death. Atovaquone was detectable in the sera, brains, livers, and lungs of mice by high-performance liquid chromatography. Development of TE and mortality in mice treated with 1.0- or 0.1-mg/kg i.v. doses of ANS did not differ from that in mice treated orally with 100 mg of atovaquone/kg. In conclusion, i.v. ANSs may prove to be an effective treatment alternative for patients with TE.
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Affiliation(s)
- N Schöler
- Institute for Infection Medicine, Department of Medical Microbiology and Immunology of Infection, Benjamin Franklin Medical Center, D-12203 Berlin, Germany
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60
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Lindegårth N, Funding L, Bergqvist Y. Automated solid-phase extraction method for the determination of atovaquone in capillary blood applied onto sampling paper by rapid high-performance liquid chromatography. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2001; 758:137-44. [PMID: 11486822 DOI: 10.1016/s0378-4347(01)00160-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A bioanalytical method for the determination of atovaquone in 100 microl blood-spots by solid-phase extraction and high-performance liquid chromatography has been developed and validated. Atovaquone was extracted from the sampling paper in 0.2 M phosphoric acid and a structurally similar internal standard was added with acetonitrile before being loaded onto a C8 end-capped solid-phase extraction column. Atovaquone and internal standard were analysed by high-performance liquid chromatography on a C18 J'Sphere ODS-M80 (150 x 4.0 mm) column with mobile phase acetonitrile-phosphate buffer, 0.01 M, pH 7.0 (65:35, v/v) and UV detection at 277 nm. The intra-assay precision was 2.7% at 12.00 microM and 13.5% at 1.00 microM. The inter-assay precision was 3.3% at 12.00 microM and 15.6% at 1.00 microM. The lower limit of quantification was 1.00 microM. The limit of detection was 0.50 microM.
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61
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Nicolaides E, Symillides M, Dressman JB, Reppas C. Biorelevant dissolution testing to predict the plasma profile of lipophilic drugs after oral administration. Pharm Res 2001; 18:380-8. [PMID: 11442280 DOI: 10.1023/a:1011071401306] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE To quantitatively compare in vitro dissolution data in biorelevant and compendial media, to investigate whether in vitro differences are reflected in the simulated plasma profile and to specify under which circumstances prediction of the plasma profile of orally administered lipophilic drugs can be achieved. METHODS Previously published dissolution data from seven products of four lipophilic drugs were compared using the first order model, the RRSBW distribution, and a model based on the Noyes-Whitney theory. Simulated plasma profiles were then obtained using a model-dependent approach. Simulated and observed plasma profiles were compared with the difference factor, f1. RESULTS No model consistently provided the best fit to the in vitro data, which varied significantly with medium composition. Prediction of the plasma profile was possible (9.6 < or = f1 < or = 34.2) in seven out of eleven cases. CONCLUSIONS Although prediction of the plasma profile of lipophilic drugs solely on the basis of in vitro data remains an ambitious target, this study shows that the plasma profile of a lipophilic drug can be predicted with appropriate in vitro dissolution data, provided that the absolute bioavailability of the drug is known and the drug has dissolution limited absorption.
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Affiliation(s)
- E Nicolaides
- Laboratory of Biopharmaceutics and Pharmacokinetics, University of Athens, Greece
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62
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Affiliation(s)
- F Nosten
- Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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63
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Lindegårdh N, Bergqvist Y. Automated solid-phase extraction method for the determination of atovaquone in plasma and whole blood by rapid high-performance liquid chromatography. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2000; 744:9-17. [PMID: 10985561 DOI: 10.1016/s0378-4347(00)00221-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A bioanalytical method for the determination of atovaquone in plasma and whole blood by solid-phase extraction and high-performance liquid chromatography has been developed and validated. A structurally similar internal standard was added and protein was precipitated from plasma and whole blood with acetonitrile before being loaded on to a C8 solid-phase extraction column. Atovaquone and internal standard were analysed by high-performance liquid chromatography on a C18 J'Sphere ODS-M80 (150x4.0 mm) column with mobile phase acetonitrile-phosphate buffer, 0.01 M, pH 7.0 (65:35, v/v) and UV detection at 277 nm. The intra-assay precisions for plasma and whole blood were 2.2% and 1.9% respectively at 12 microM and 6.0% and 5.6% respectively at 0.75 microM. The inter-assay precisions for plasma and whole blood were 1.4% and 2.1% respectively at 12 microM and 4.9% and 3.4% respectively at 0.75 microM. The lower limit of quantification in plasma and whole blood were 150 nM. The limit of detection in plasma and whole blood were 30 nM.
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64
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Chou CC, Brown MP, Merritt KA. Capillary zone electrophoresis for the determination of atovaquone in serum. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2000; 742:441-5. [PMID: 10901150 DOI: 10.1016/s0378-4347(00)00183-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A rapid and simple capillary zone electrophoresis (CZE) method has been developed for the determination of atovaquone in serum. The drug was extracted from equine serum-chloroform (1:3, v/v) at greater than 80% recovery and assayed in buffer containing 25 mM sodium borate (pH 9.1) and 25% acetonitrile. A 100 microm I.D. fused-silica capillary was used and the detection was by UV-diode array at 254 nm; the migration time was approximately 8 min. Intra- and inter-assay variabilities were less than 7.8% and 5.8%, respectively, and the accuracy of the assay (expressed as % bias) ranged from 4.5 to -5.2%. The working assay range was from 2 to 100 microg/ml. This sensitivity could be increased by concentrating during the extraction procedure. Replacement of acetonitrile with 75 mM surfactant 3-(dimethyldodecylammonio)propanesulfonate gave similar sensitivity and provided an additional option to facilitate the separation of atovaquone on multiple-drug samples.
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Affiliation(s)
- C C Chou
- Department of Large Animal and Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32610, USA.
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65
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Bergqvist Y, Hopstadius C. Simultaneous separation of atovaquone, proguanil and its metabolites on a mixed mode high-performance liquid chromatographic column. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2000; 741:189-93. [PMID: 10872588 DOI: 10.1016/s0378-4347(00)00082-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An isocratic high-performance liquid chromatographic (HPLC) method for simultaneous separation of the components in the antimalarial combination drug Malarone with UV detection is described. An HPLC system using a mixed mode column composed of 50% C(18) phase and 50% strong cation-exchanger has been optimised for the simultaneous separation of atovaquone, proguanil and its two main metabolites. The mobile phase was optimised for factors such as pH, counter ion concentration and acetonitrile. Elimination of interferences from other antimalarial drugs was achieved by adding sodium perchlorate to the mobile phase. With a mobile phase of acetonitrile-phosphate buffer (60:40, v/v) pH 6.8, 50.7 mmol l(-1) K+ and 10 mmol l(-1) Na x ClO4, separation was achieved within a run time shorter than 17 min.
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Affiliation(s)
- Y Bergqvist
- Dalarna University College, Division of Clinical Pharmacology, Karolinska Institute, Huddinge University Hospital, Sweden.
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66
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Nicolaides E, Galia E, Efthymiopoulos C, Dressman JB, Reppas C. Forecasting the in vivo performance of four low solubility drugs from their in vitro dissolution data. Pharm Res 1999; 16:1876-82. [PMID: 10644077 DOI: 10.1023/a:1018959511323] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE To assess the usefulness of biorelevant dissolution tests in predicting food and formulation effects on the absorption of four poorly soluble, lipophilic drugs. METHODS. Dissolution was studied with USP Apparatus II in water, milk, SIFsp, FaSSIF, and FeSSIF. The in vitro dissolution data were compared on a rank order basis with existing in vivo data for the tested products under fasted and fed state conditions. RESULTS All drugs/formulations showed more complete dissolution in bile salt/lecithin containing media and in milk than in water and SIFsp (USP 23). Comparisons of the in vitro dissolution data in biorelevant media with in vivo data showed that in all cases it was possible to forecast food effects and differences in absorption between products of the same drug with the physiologically relevant media (FaSSIF, FeSSIF and milk). Differences between products (both in vitro or in vivo) were less pronounced than differences due to media composition (in vitro) or dosing conditions (in vivo). CONCLUSIONS Although biorelevant dissolution tests still have issues which will require further refinement, they offer a promising in vitro tool for forecasting the in vivo performance of poorly soluble drugs.
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Affiliation(s)
- E Nicolaides
- Department of Pharmacy, University of Athens, Greece
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67
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Falloon J, Sargent S, Piscitelli SC, Bechtel C, LaFon SW, Sadler B, Walker RE, Kovacs JA, Polis MA, Davey RT, Lane HC, Masur H. Atovaquone suspension in HIV-infected volunteers: pharmacokinetics, pharmacodynamics, and TMP-SMX interaction study. Pharmacotherapy 1999; 19:1050-6. [PMID: 10610011 DOI: 10.1592/phco.19.13.1050.31598] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
STUDY OBJECTIVE To evaluate the pharmacokinetics and safety of atovaquone suspension in volunteers infected with the human immunodeficiency virus ((HIV). DESIGN Open-label, nonrandomized study. SETTING Two clinical research centers. PATIENTS Twenty-two HIV-infected volunteers with a median CD4 cell count of 37 cells/mm3. INTERVENTIONS Patients received atovaquone suspension fasting or fed for 2-week periods with crossover at dosages of 500 mg/day, and randomization to fasting or fed at dosages of 750 and 1000 mg/day. A subset of patients also received 750 mg twice/day with food, and a subset of those who received 1000 mg/day fasting also received 1000 mg with food. During a long-term dosing phase, a subset of subjects were evaluated for an interaction between atovaquone and trimethoprim-sulfamethoxazole (TMP-SMX). MEASUREMENTS AND MAIN RESULTS Average steady-state atovaquone concentrations at 500 mg were 6.7 +/- 3.2 microg/ml fasted and 11.3 +/- 5.0 microg/ml with food; at 750 mg, 9.9 +/- 7.1 microg/ml fasted and 12.5 +/- 5.9 microg/ml with food; at 1000 mg, 9.7 +/- 4.3 microg/ml fasted and 13.6 +/- 5.0 microg/ml with food; and at 1500 mg, 21.1 +/- 5.0 microg/ml with food. Thus, plasma concentrations were not proportional to dose. Concomitant food ingestion resulted in a 1.3- to 1.7-fold increase in values. Average steady-state concentrations were less than 10 microg/ml in 21% and more than 15 microg/ml in 36% of patients at 1000 mg/day with food; at 750 mg twice/day, all five patients had levels above 15 microg/ml. Atovaquone suspension was well tolerated; diarrhea, nausea, fatigue, and rash were the most common adverse events. Concomitant administration of TMP-SMX did not change atovaquone concentrations and resulted in small decreases in concentrations of TMP (16%) and SMX (10%). CONCLUSION Plasma concentrations are significantly higher when atovaquone suspension is administered with food compared with fasting. Total doses of 1500 mg/day are likely to achieve concentrations effective for prophylaxis of Pneumocystis carinii pneumonia.
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Affiliation(s)
- J Falloon
- National Institute of Allergy and Infectious Diseases and the Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland 20892-1880, USA
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68
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Mulenga M, Sukwa TY, Canfield CJ, Hutchinson DB. Atovaquone and proguanil versus pyrimethamine/sulfadoxine for the treatment of acute falciparum malaria in Zambia. Clin Ther 1999; 21:841-52. [PMID: 10397379 DOI: 10.1016/s0149-2918(99)80006-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Atovaquone and proguanil hydrochloride are blood schizonticides that demonstrate in vitro synergy against drug-resistant strains of Plasmodium falciparum. When coadministered, they may therefore be effective for the treatment of malaria in regions where there is known or suspected drug resistance. In an open-label, randomized, parallel-group, clinical trial conducted in Zambia, 163 patients (age range, 14 to 54 years) with acute P falciparum malaria were randomly assigned to receive treatment with atovaquone and proguanil hydrochloride (1000 and 400 mg, respectively, administered orally at 24-hour intervals for 3 doses; n = 82) or pyrimethamine/sulfadoxine (75/1500 mg administered orally as a single dose; n = 81). Efficacy was assessed by cure rate (the percentage of patients in whom parasitemia was eliminated and did not recur during 28 days of follow-up), parasite clearance time (PCT), and fever clearance time (FCT). Safety was determined by sequential clinical and laboratory assessments over 28 days. Cure rates did not differ significantly between patients treated with atovaquone and proguanil (100%) and those treated with pyrimethamine/sulfadoxine (98.8%). Patients in the atovaquone and proguanil group had a significantly shorter FCT than patients in the pyrimethamine/sulfadoxine group (mean, 30.4 vs 44.9 hours; P < 0.05) but a longer PCT (mean, 64.0 vs 51.4 hours; P < 0.05). Both treatments were well tolerated; adverse events and laboratory abnormalities were typical of those normally observed in patients with malaria. In this study, the combination of atovaquone and proguanil was equally effective and as well tolerated as pyrimethamine/sulfadoxine for the treatment of acute, uncomplicated, drug-resistant falciparum malaria in Zambia.
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Affiliation(s)
- M Mulenga
- Tropical Diseases Research Centre, Ndola, Zambia, Africa
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69
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Pearson PA, Piracha AR, Sen HA, Jaffe GJ. Atovaquone for the treatment of toxoplasma retinochoroiditis in immunocompetent patients. Ophthalmology 1999; 106:148-53. [PMID: 9917796 DOI: 10.1016/s0161-6420(99)90021-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
OBJECTIVE To report the results of a phase I trial to evaluate the safety and efficacy of atovaquone for the treatment of ocular toxoplasmosis in immunocompetent patients. DESIGN Open label, nonrandomized, prospective, clinical trial. PARTICIPANTS Seventeen immunocompetent patients between the ages of 18 and 75 years with clinical and serologic evidence of ocular toxoplasmosis participated. INTERVENTION Treatment of ocular toxoplasmosis with atovaquone tablets (750 mg four times a day) for 3 months. Prednisone (40 mg) tablets were added on day 3 of treatment and tapered as inflammation resolved. MAIN OUTCOME MEASURES Clinical response and patient tolerance to atovaquone therapy for ocular toxoplasmosis. RESULTS Average follow-up was 10 months. Most patients experienced no adverse treatment effects. When present, side effects were usually mild and included rash, pruritus, headache, and nausea. With the exception of one patient, who discontinued treatment at 6 weeks secondary to persistent epigastric discomfort, all patients completed the 12 weeks of therapy. All patients had a favorable response to treatment that began within 1 to 3 weeks. Visual acuity was stabilized or improved in all patients. Median initial visual acuity was 20/200 and median final visual acuity was 20/25. In general, atovaquone was well tolerated. CONCLUSIONS Atovaquone is better tolerated than conventional antitoxoplasmosis therapy and appears to be at least as effective. Atovaquone is a promising alternative for the treatment of ocular toxoplasmosis in immunocompetent patients.
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Affiliation(s)
- P A Pearson
- Department of Ophthalmology, University of Kentucky, Lexington 40536, USA
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70
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Freeman CD, Klutman NE, Lamp KC, Dall LH, Strayer AH. Relative bioavailability of atovaquone suspension when administered with an enteral nutrition supplement. Ann Pharmacother 1998; 32:1004-7. [PMID: 9793589 DOI: 10.1345/aph.17464] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
OBJECTIVE To compare the relative bioavailability of a single atovaquone 750 mg suspension oral dose when administered in the fasting state, after a normal breakfast, and after an enteral nutrition supplement. DESIGN Ten healthy volunteers received a single dose of atovaquone suspension 750 mg/5 mL while fasting. At 2-week intervals, the subjects were then randomized in a crossover design to receive the atovaquone dose within 1 hour of consuming a normal breakfast (fat content 21 g) and 16 oz. of Sustacal Plus (fat content 28 g). Blood samples were collected at seven time points after each atovaquone dose. HPLC was used to determine the atovaquone concentrations in plasma. RESULTS Administering atovaquone suspension with either a normal breakfast or an enteral nutrition supplement, such as Sustacal Plus, significantly increased the oral relative bioavailability. The mean AUC0-24 after the fasting dose was 43.4 micrograms.h/mL. The mean AUC0-24 values with breakfast (103.8 micrograms.h/mL) and Sustacal Plus (118.8 micrograms.h/mL) were significantly greater compared with fasting (p < 0.0001). CONCLUSIONS This study has shown that the new atovaquone oral suspension also has significantly greater bioavailability when administered after food or a nutrition supplement that has a moderate fat content. Patients who require atovaquone therapy can use Sustacal Plus without risk of reduced absorption.
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Affiliation(s)
- C D Freeman
- School of Medicine, University of Missouri-Kansas City, USA
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71
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Yeo AE, Edstein MD, Rieckmann KH. Antimalaria activity of the triple combination of proguanil, atovaquone and dapsone. Acta Trop 1997; 67:207-14. [PMID: 9241385 DOI: 10.1016/s0001-706x(97)00060-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The combination of proguanil and atovaquone has been shown to be more effective in curing drug-resistant infections of falciparum malaria than atovaquone or proguanil alone. Our current study sought to determine whether the antimalaria activity could be increased by adding dapsone. Plasma samples, obtained from individuals 4-72 h after proguanil-atovaquone administration, were 2-3 times more active against Plasmodium falciparum in vitro when dapsone was added to them. The enhanced activity of the combination of proguanil, atovaquone and dapsone is probably due to the combined activity of two synergistic combinations: proguanil-atovaquone and cycloguanil (metabolite of proguanil)-dapsone. These findings suggest that further studies are needed to evaluate the clinical value of the triple drug combination of proguanil, atovaquone and dapsone in the treatment of multi-drug resistant malaria.
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Affiliation(s)
- A E Yeo
- Australian Army Malaria Research Unit, Liverpool Military Area, NSW, Australia.
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72
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73
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Goldman P. Olestra: assessing its potential to interact with drugs in the gastrointestinal tract. Clin Pharmacol Ther 1997; 61:613-8. [PMID: 9209243 DOI: 10.1016/s0009-9236(97)90094-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- P Goldman
- Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA
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74
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Rolan PE, Mercer AJ, Tate E, Benjamin I, Posner J. Disposition of atovaquone in humans. Antimicrob Agents Chemother 1997; 41:1319-21. [PMID: 9174191 PMCID: PMC163907 DOI: 10.1128/aac.41.6.1319] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Atovaquone is an antiprotozoal compound with good in vitro stability against metabolic inactivation. Previous human studies which did not involve radiolabelling had not accounted for a substantial proportion of the dose. The possible metabolism of atovaquone in men was examined in a radiolabelling study involving four healthy male volunteers. Radioactivity was eliminated almost exclusively via the feces. All radioactivity in plasma, urine, and feces was accounted for by atovaquone, with no evidence of metabolites. Radiolabelled atovaquone was administered to a patient with an indwelling biliary tube after surgery. Biliary radioactivity was approximately 10- to 40-fold higher than that in plasma and was accounted for by atovaquone. Atovaquone is not significantly metabolized in humans but is excreted into bile against a high concentration gradient.
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Affiliation(s)
- P E Rolan
- Department of Clinical Pharmacology, Wellcome Research Laboratories, Beckenham, Kent, United Kingdom
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75
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Hussein Z, Eaves J, Hutchinson DB, Canfield CJ. Population pharmacokinetics of atovaquone in patients with acute malaria caused by Plasmodium falciparum. Clin Pharmacol Ther 1997; 61:518-30. [PMID: 9164414 DOI: 10.1016/s0009-9236(97)90132-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The population pharmacokinetics of atovaquone were examined in 458 black, Oriental, and Malay patients with acute Plasmodium falciparum malaria receiving atovaquone alone or concomitantly with other drugs. Oral clearance (CL/F) showed a 0.674 power relationship with weight and is similar in Oriental and Malay subjects but 58.5% lower in black subjects. On the basis of mean body weight, the population estimate of CL/F is 3.28, 8.49, and 9.13 L/hr in black, Oriental, and Malay subjects, respectively. The relationship between apparent volume of distribution (V area/F) and weight was linear and similar in all three races at 7.98 L/kg. The population estimate of V area/F is 345, 383, and 428 L in black, Oriental, and Malay subjects, respectively. The bioavailability of the high and low doses of atovaquone was similar. Neither CL/F nor V area/F were significantly affected by age, gender, and the coadministration with chloroguanide (proguanil), pyrimethamine, and tetracycline. Half-life (t1/2) showed a 0.326 power relationship with weight; thus, the population estimate of t1/2 in black, Oriental, and Malay subjects is 72.9, 31.3, and 32.5 hours, respectively. The final magnitudes of interpatient variability in CL/F and V area/F were 68% and 49%, respectively.
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Affiliation(s)
- Z Hussein
- Glaxo Wellcome, Beckenham, and Pharmaceutical Systems Inc., Talent, Oregon, USA
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76
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Charman WN, Porter CJ, Mithani S, Dressman JB. Physiochemical and physiological mechanisms for the effects of food on drug absorption: the role of lipids and pH. J Pharm Sci 1997; 86:269-82. [PMID: 9050793 DOI: 10.1021/js960085v] [Citation(s) in RCA: 399] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Drugs are absorbed after oral administration as a consequence of a complex array of interactions between the drug, its formulation, and the gastrointestinal (GI) tract. The presence of food within the GI tract impacts significantly on transit profiles, pH, and its solubilization capacity. Consequently, food would be expected to affect the absorption of co-administered drugs when their physicochemical properties are sensitive to these changes. The physicochemical basis by which ingested food/lipids induce changes in the GI tract and influence drug absorption are reviewed. The process of lipid digestion is briefly reviewed and considered in the context of the absorption of poorly water-soluble drugs. The effect of food on GI pH is reviewed in terms of location (stomach, upper and lower small intestine) and the temporal relationship between pH and drug absorption. Case studies are presented in which postprandial changes in bioavailability are rationalized in terms of the sensitivity of the physicochemical properties of the administered drug to the altered GI environment.
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Affiliation(s)
- W N Charman
- Department of Pharmaceutics, Victorian College of Pharmacy, Monash University (Parkville Campus), Victoria, Australia
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77
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Edstein MD, Yeo AE, Kyle DE, Looareesuwan S, Wilairatana P, Rieckmann KH. Proguanil polymorphism does not affect the antimalarial activity of proguanil combined with atovaquone in vitro. Trans R Soc Trop Med Hyg 1996; 90:418-21. [PMID: 8882194 DOI: 10.1016/s0035-9203(96)90531-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Clinical studies have shown proguanil (PROG) combined with atovaquone (ATQ) to be an effective and safe antimalarial combination for the treatment of multidrug-resistant falciparum malaria. PROG is a prodrug, which undergoes hepatic metabolism to its pharmacologically active metabolite cycloguanil (CYC). Individuals exhibit genetic polymorphism with respect to PROG, and can be phenotyped as either extensive metabolizers (EMs) or poor metabolizers (PMs) by measuring their PROG/CYC concentration ratio in plasma following PROG/ATQ administration. PMs produce lower plasma concentrations of CYC than EMs and thus may be more susceptible to prophylaxis or treatment failure. Both PROG and CYC potentiate the activity of ATQ in vitro. The antimalarial activity ex vivo of Thai patients' plasma samples obtained from EMs and PMs given concurrent PROG and ATQ was studied using the K1 isolate of Plasmodium falciparum. This isolate is resistant to PROG and CYC, but sensitive to ATQ. Maximum inhibitory dilution profiles of the patients' plasma samples containing PROG and ATQ from EMs and PMs were similar. These findings indicate that differences in plasma drug concentrations between EMs and PMs did not alter the antimalarial activity in vitro against the K1 isolate. The phenotypic status of individuals is not an important issue in the treatment of patients with PROG/ATQ.
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Affiliation(s)
- M D Edstein
- Army Malaria Research Unit, Sydney, Australia
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78
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Dixon R, Pozniak AL, Watt HM, Rolan P, Posner J. Single-dose and steady-state pharmacokinetics of a novel microfluidized suspension of atovaquone in human immunodeficiency virus-seropositive patients. Antimicrob Agents Chemother 1996; 40:556-60. [PMID: 8851570 PMCID: PMC163157 DOI: 10.1128/aac.40.3.556] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The single- and multiple-dose pharmacokinetics of and tolerability to a new microfluidized suspension of atovaquone were studied in human immunodeficiency virus-seropositive patients with CD4 counts of < or = 200 cells per mm3 in order to define a dosing regimen for the treatment of Pneumocystis carinii pneumonia. This was an open study with groups of six patients each. In the first part of the study, six subjects received escalating single doses of 500, 1,000, and 1,500 mg after an overnight fast at weekly intervals. In the second part of the study, groups of six subjects were dosed for 14 days according to three regimens: 1,000 mg twice daily fasting, twice daily with a high-fat meal, or once daily with a high-fat meal. Plasma atovaquone levels were assayed by high-performance liquid chromatography. Pharmacokinetic parameters were determined by noncompartmental methods, and statistical comparison of parameters for single doses was performed by analysis of variance. Plasma drug concentrations increased with single doses from 500 to 1,000 mg but were no higher with a dose of 1,500 mg. Thus, 1,000 mg was selected for multiple administration. A regimen of 1,000 mg twice daily with food resulted in a 93% increase in the average trough steady-state concentration compared with 1,000 mg once daily with food. Food increased the bioavailability of atovaquone 1.4-fold over that in the fasting state. All patients who received 1,000 mg twice daily with food achieved target steady-state concentrations in plasma of 15 to 25 micrograms/ml. Multiple-dose regimens were generally well tolerated, but the higher levels in plasma achieved by 1,000 mg twice daily with food were associated with an increased incidence of rash. In conclusion, target plasma atovaquone concentrations for the treatment of P. carinii pneumonia can be achieved in most patients with 1,000 mg twice daily in a fasting state and in all patients with 1,000 mg twice daily administered with food, but at higher concentrations in plasma, there may be an increased risk of rash.
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Affiliation(s)
- R Dixon
- Department of Clinical Pharmacology, Wellcome Research Laboratories, Kent, United Kingdom
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79
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Hansson AG, Mitchell S, Jatlow P, Rainey PM. Rapid high-performance liquid chromatographic assay for atovaquone. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL APPLICATIONS 1996; 675:180-2. [PMID: 8634763 DOI: 10.1016/0378-4347(95)00329-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A rapid high-performance liquid chromatography assay has been developed for the drug atovaquone, which is currently being used to treat Pneumocystis carinii pneumonia and Toxoplasma gondii encephalitis associated with the acquired immunodeficiency syndrome (AIDS). Protein is precipitated from plasma with acetonitrile-aqueous 1% acetic acid (85:15). The supernatant is assayed on a C6 column using methanol-10 mM triethylamine in aqueous 0.2% trifluoroacetic acid (76:24) with detection at 254 nm. The working assay range was 0.5 to 50 micrograms/ml. Recovery was 97% and the between-day coefficients of variation were 2.1% at 50 micrograms/ml and 10.3% at 1 microgram/ml. A number of drugs commonly used to treat AIDS and its complications did not interfere with the assay.
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Affiliation(s)
- A G Hansson
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520-8035, USA
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80
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Affiliation(s)
- J Zhi
- Department of Clinical Pharmacokinetics, Hoffmann-La Roche, Inc., Nutley, NJ 07110-1199, USA
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81
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Studenberg SD, Long JD, Woolf JH, Bruner CJ, Wilson D, Woolley JL. A robotics-based liquid chromatographic assay for the measurement of atovaquone in plasma. J Pharm Biomed Anal 1995; 13:1383-93. [PMID: 8634356 DOI: 10.1016/0731-7085(95)01563-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A precise and specific robotics-based liquid chromatographic (LC) method for measuring atovaquone concentrations in plasma was developed and validated, and the method was compared with an existing manual LC method. The compound was isolated from plasma by liquid-liquid extraction, separated by reversed-phase LC, and quantitated against an internal standard with UV detection. Least-squares linear regression with 1/concentration2 weighting was used as the calibration model. The range of the calibration curve for the assay under routine conditions was 0.25-50 micrograms ml-1. No endogenous interferences with the compound or the internal standard were noted in either untreated human plasma or in plasma from patients enrolled in Phase III clinical trials of atovaquone. The accuracy of the assay (determined as the percent bias) ranged from -4.8% to -9.4% in the validation runs. The intra- and interassay precisions (determined as the relative standard deviation) were less than 6.8% and 6.4%, respectively. The contribution of an internal standard on assay accuracy and precision also was examined. Interassay variability was marginally improved by the incorporation of an internal standard to the assay; accuracy and intra-assay precision were essentially unchanged. A paired t-test between estimates of atovaquone concentrations in healthy volunteer and HIV + patient human plasma samples assayed by the automated and manual methods demonstrated no significant difference (p = 0.31) between the values determined by each method.
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Affiliation(s)
- S D Studenberg
- Division of Pharmacokinetics and Drug Metabolism, Wellcome Research Laboratories, Research Triangle Park, NC 27709, USA
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82
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Spencer CM, Goa KL. Atovaquone. A review of its pharmacological properties and therapeutic efficacy in opportunistic infections. Drugs 1995; 50:176-96. [PMID: 7588086 DOI: 10.2165/00003495-199550010-00011] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Atovaquone has been investigated as an alternative agent for oral use in the treatment of both mild to moderate Pneumocystis carinii pneumonia (PCP) and toxoplasmosis, opportunistic infections commonly experienced by patients with AIDS. In patients with mild to moderate PCP, a dosage of 750mg 3 times daily (administered in tablet form) has similar overall therapeutic efficacy (defined as clinical response without a treatment-limiting adverse event) to the conventional therapies oral cotrimoxazole (trimethoprim-sulfamethoxazole) and intravenous pentamidine, respectively. Response rates to atovaquone are lower than those achieved with cotrimoxazole, but atovaquone has superior tolerability. Atovaquone recipients experienced significantly fewer treatment-limiting adverse effects than patients treated with cotrimoxazole (7 vs 20%) or pentamidine (4 vs 36%). Mortality rates were higher among atovaquone-treated patients than in cotrimoxazole recipients (7 vs 0.6%) 4 weeks after completion of therapy in a large comparative trial, although most deaths were caused by bacterial infections. However, a similar rate of mortality was reported for atovaquone- and pentamidine-treated patients (16 vs 17% 8 weeks after discontinuation of therapy) in another study. In predominantly small numbers of patients with toxoplasmosis, of whom most were unresponsive to conventional agents, atovaquone 750mg 4 times daily (administered as tablets) produced a complete or partial radiological response rate of 37 to 87.5% 52% of patients achieved a complete or partial clinical response after 6 weeks of treatment in the largest trial (n = 87), although the incidence of toxoplasmosis-related death was 24% 18 weeks after therapy was initiated. Thus, atovaquone will be a useful option for the treatment of patients with mild to moderate PCP who are intolerant or unresponsive to cotrimoxazole, especially if the increased plasma drug concentrations observed with the suspension further improve response rates. Atovaquone should also be considered a promising agent for the treatment of toxoplasmosis.
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Affiliation(s)
- C M Spencer
- Adis International Limited, Auckland, New Zealand
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