Pharmacokinetics and hemodynamic effects of single oral doses of thalidomide in asymptomatic human immunodeficiency virus-infected subjects

Severe postural hypotension and sinus bradycardia with thalidomide in patients with erythema nodosum leprosum

Two men in their 60s and 40s were diagnosed with erythema nodosum leprosum based on the development of recurrent painful ulcers and nodules, respectively, for the previous 6 months. Thalidomide 100 mg four times a day, along with MB-MDT, was started in both patients. Both patients experienced severe dizziness on rising from a seated posture soon after initiation of thalidomide and a decrease in blood pressure and heart rate. Cardiovascular/neurology examination and routine blood investigations were normal. An autonomic nervous system assessment indicated bradycardia, postural hypotension and decreased cardiac autonomic function. The dosage of thalidomide was then gradually reduced over 4-5 days to 100 mg/day following a suspicion that thalidomide was the cause of postural hypotension. The dizziness subsided, and blood pressure and heart rate returned to normal.We concluded that thalidomide was the culprit behind bradycardia and dose- dependent postural hypotension.

Safety and pharmacokinetics of thalidomide in tumor-bearing dogs

Thalidomide, an angiogenesis inhibitor, has recently been used to treat malignant canine tumors. This study retrospectively investigated the adverse events (AEs) of thalidomide administered to tumor-bearing dogs. We investigated the pharmacokinetics of thalidomide after administration and the rate of body weight change before and after administration. The initial thalidomide dose was 5 mg/kg per os once daily, which was increased to 10 mg/kg once daily in dogs with no significant AEs. Pharmacokinetics were measured in four dogs after the 5 mg/kg or 10 mg/kg dose. We evaluated AEs related to clinical signs in 51 patients; 9/51 had lethargy, 6/51 had tremor, 4/51 had dizziness, 31/51 had decreased appetite, 8/51 had vomiting, and 16/49 had soft stool/diarrhea. We evaluated hematologic toxicity in 44 patients with grade 3 or higher adverse events; 1/44 had thrombocytopenia, 1/44 had increased blood urea nitrogen concentrations, and 5/44 had increased alanine aminotransferase activities. The mean thalidomide blood levels were Cmax=1.4 ± 0.7 μg/mL (Area under the curve [AUC]0-24=8.5 ± 4.7 μg•hr /mL) and Cmax=3.2 ± 2.1 μg/mL (AUC0-24=22.0 ± 14.7 μg•hr/mL) in the 5 mg/kg and 10 mg/kg groups, respectively. The Cmax and AUC in the 10 mg/kg group were comparable to the effective blood concentrations seen in humans administered thalidomide. The weight fluctuation rates were assessed in 24 dogs approximately 1 month after the start of thalidomide administration; more than half showed weight maintenance or gain. Most AEs were clinically acceptable; however, peripheral nerve signs were seen in some dogs.

Population Pharmacokinetic Model to Assess the Impact of Disease State on Thalidomide Pharmacokinetics

A population pharmacokinetic (PPK) model to describe the pharmacokinetics of thalidomide in different patient populations was developed using data pooled from healthy subjects and patients with Hansen's disease, human immunodeficiency virus (HIV), and multiple myeloma (MM). The analysis data set had a total of 164 evaluable subjects who received various doses (50 to 400 mg) of oral thalidomide in single- and/or multiple-dose regimens. The plasma thalidomide concentrations were adequately described by a linear 1-compartment PPK model with first-order absorption and first-order elimination. Inclusion of MM as a covariate on apparent clearance (CL/F) accounted for 4.4% of the interindividual variability (IIV) of CL/F. Body weight as a covariate on CL/F and apparent volume of distribution (V/F) also improved model fitting slightly, accounting for 7.2% and 20% of IIV, respectively. Although inclusion of body weight and MM as covariates of CL/F and body weight on V/F improved the goodness of fit of the model in a statistically significant manner, the impact of this difference in CL/F is not considered clinically relevant. Other factors such as age, sex, race, creatinine clearance, and alanine transaminase had no effect on thalidomide pharmacokinetics. MM, HIV, and Hansen's disease have no clinically relevant effect on thalidomide disposition relative to healthy volunteers.

Plasma and cerebrospinal fluid pharmacokinetics of thalidomide and lenalidomide in nonhuman primates

PURPOSE

Thalidomide, originally developed as a sedative, was subsequently identified to have antiangiogenic properties. Lenalidomide is an antiangiogenic and immunomodulatory agent that has been utilized in the treatment of patients with brain tumors. We studied the pharmacokinetics and cerebrospinal fluid (CSF) penetration of thalidomide and lenalidomide in a nonhuman primate model.

METHODS

A dose of 50 mg of thalidomide or 20 mg of lenalidomide was administered once orally to each of three rhesus monkeys. Plasma and CSF samples were obtained at specified intervals, and the thalidomide or lenalidomide concentrations were determined by high-performance liquid chromatography with tandem mass spectrometry. Pharmacokinetic parameters were estimated using noncompartmental methods. CSF penetration was calculated as area under the concentration-time curve (AUC) CSF/AUC plasma.

RESULTS

For thalidomide, the median apparent clearance (Cl/F) was 2.9 mL/min/kg, the median plasma AUC was 80 μM h, and the median terminal half-life (t(½)) was 13.3 h. For lenalidomide, the median Cl/F was 8.7 mL/min/kg, the median AUC was 9 μM h, and the median t(½) was 5.6 h. Thalidomide was detected in the CSF of all animals, with a median penetration of 42%. Lenalidomide was detected in the CSF of 2 of 3 animals, with a CSF penetration of 11% in each.

CONCLUSION

Thalidomide and lenalidomide penetrate into the CSF after oral administration of clinically relevant doses. Plasma exposure to lenalidomide was similar in our model to that observed in studies involving children who have brain tumors. These results support further development of lenalidomide for the treatment of central nervous system malignancies.

Pharmacokinetics of thalidomide in patients with impaired renal function and while on and off dialysis

There is a renewed interest in thalidomide for use in malignancies and systemic inflammatory diseases. Reduced renal function is not uncommon among patients with these disease states but the pharmacokinetics has not been fully investigated. The aim of this study was to investigate the pharmacokinetics of thalidomide in haemodialysis patients while on and off dialysis and in myeloma patients with varying degrees of renal function.

Two studies were performed. To establish the pharmacokinetics of thalidomide in patients with mild to moderate renal failure, blood samples were taken over 12 weeks from 40 patients with multiple myeloma. A second study was performed in six patients with end-stage renal disease both on a non-dialysis day and before and during a haemodialysis session. Thalidomide concentration was determined by HPLC. A one-compartment open model with first-order absorption and elimination was used to fit total thalidomide concentration to population pharmacokinetics and statistical models using the NONMEM program. Clearance and volumes were slightly below 10 L h−1 and 1 L kg−1, respectively, in both patient groups. The inter- and intra-patient variability was low. Clearance was doubled during dialysis. There was no correlation between thalidomide clearance and renal function. In conclusion, the pharmacokinetics of thalidomide in patients with renal failure are very similar to values reported by others for patients with normal renal function. Although clearance during dialysis is doubled, thalidomide dose need not be changed for patients with decreased kidney function. There is also no need for a supplementary dose due to haemodialysis.

Phase II and pharmacokinetic study of thalidomide in Japanese patients with relapsed/refractory multiple myeloma

To obtain approval from the Ministry of Health, Labor and Welfare of Japan, a phase II study was conducted to assess the pharmacokinetics and pharmacodynamics of thalidomide along with its efficacy and safety in Japanese patients with multiple myeloma. Between 2005 and 2006, 42 patients were enrolled, and 37 patients met eligibility criteria. Of the 37 patients, 3 were excluded from efficacy analysis because of short duration of thalidomide administration (<4 weeks). The overall response rate was 35.3% (12/34), including partial response of 14.7% (5/34) and minimal response of 20.6% (7/34). The adverse events observed in high frequency (>40%) were leukopenia, neutropenia, drowsiness, dry mouth, and constipation. Grade 3 neutropenia was observed in nine cases. Peripheral neuropathy and eruption were observed in about one-quarter of the patients. Deep vein thrombosis was not observed. At a single oral dose of thalidomide (100 mg), the C (max) was 1.68 +/- 0.41 microg/ml, T (max) was 4.54 +/- 1.71 h, T (1/2) was 4.86 +/- 0.44 h, and AUC was 15.87 +/- 3.05 microg h/ml. Low-dose thalidomide was an effective and tolerable treatment for Japanese patients with relapsed/refractory myeloma. Leukopenia and neutropenia were the most serious adverse events. The pharmacokinetics was similar to those observed in Caucasian patients.

[Comparison of dissolution profile and plasma concentration-time profile of the thalidomide formulations made by Japanese, Mexican and British companies]

Thalidomide is an important advance in the treatment of multiple myeloma. In Japan thalidomide is now on the approval step for the treatment of multiple myeloma. The drug has some bothersome side effects such as defect of organogenesis, neuropathy, constipation and fatigue, but is likely more effective than standard chemotherapy and is changing multiple myeloma treatment. At this moment, Japanese patients must import the thalidomide preparations from Mexico, Britain and elsewhere, but after approval, they patients will be able to get the new Japanese thalidomide capsules. In order to determine appropriate amounts of Japanese thalidomide capsules in the treatment of multiple myeloma, we compared the dissolution profile and plasma thalidomide concentrations of Japanese and British capsules and Mexican tablets. The dissolution test was performed according to the Japanese and the United States Pharmacopoeia. The pharmacokinetic data for Japanese capsules were obtained from the clinical trial in Japanese subjects and compared with those data published for other formulations. The dissolution rate of the Japanese capsule was the fastest, followed by British and Mexican formulations. The pharmacokinetic profiles of Japanese and British capsules were similar, while the 100 mg Japanese thalidomide capsule demonstrated a 1.6-fold higher maximum plasma concentration than the 200 mg Mexican thalidomide tablet (1.7 vs. 1.1 microg/ml), greatly shortened t(max) (4.5 vs. 6.2 h), and the apparent half life was only one-third of the Mexican tablet (4.8 vs. 13.5 h). A comparison of the dissolution and the pharmacokinetic absorption profiles demonstrated a rank-order correlation. Physicians and pharmacists should be aware of the probable alteration in plasma thalidomide concentration when switching to the Japanese capsule, especially from the Mexican tablet, and should monitor clinical response carefully.

High performance liquid chromatographic determination of thalidomide in patients affected by hepatocellular carcinoma

The present study developed a validate and precise reversed-phase high performance liquid chromatography (HPLC) method for the determination of thalidomide (T) in plasma, to quantify T in patients affected by hepatocellular carcinoma. Twelve male subjects aging from 62 to 82 years and weighting 66-88kg, were orally administered with single dose of T (200mg/BW). Two ml of stabilizer-solution (CH3OH/CH3CN, 1/1 (v/v)+CH3COOH 2%) were added to 1ml of human plasma and stoked to -80 degrees C until analyses. This moisture (1.38microl) was added with 20microl of CF3COOH and 100microl of phthalimide (IS) 1.75microg/ml, vortexed and centrifuged. Surnatant (800microl) was dried under vacuum at room temperature, added with 50microl of appropriate solution and injected onto HPLC. T and IS were detected at UV wavelength of 220nm with a run time of 10min. Mobile phase was 10mM pH 5.5NH4+CH3COO-/CH3CN, 75/25 (v/v) buffer at flow rate of 1.5ml/min. Inter-day and intra-day variation coefficient was <10% with an error of accuracy <10%. The present detection method was able to quantify T to every withdrawal time period (LOD 0.05microg/ml). The IS used in the present study had the same wavelength maximum absorption of T, differently from early UV detection methods reported in literature where phenacetin was used. Pharmacokinetic parameters belonging from the present study are not significantly different from those calculated in previously studies performed in human health subjects and patients affected by other pathology.

Thalidomide in multiple myeloma

Multiple myeloma is an incurable bone marrow cancer, the treatment of which is notoriously difficult. Only modest advances have been achieved using complex polychemotherapeutic regimens, transplant strategies and supportive therapy. In 1999, when new drugs for myeloma were urgently needed, thalidomide was introduced and opened up a completely new line of therapy for the disease. Although the mechanism of action is not yet completely understood, thalidomide has demonstrated efficacy in patients with refractory, relapsed myeloma, even in late-stage cases. This article reviews the current knowledge of thalidomide in myeloma treatment, focusing especially on the possible mechanisms of action, clinical results and adverse events of this drug.

Thalidomide: an old drug with new clinical applications

Thalidomide has several targets and mechanisms of action: a hypnosedative effect, several immunomodulatory properties with an effect on the production of TNF-alpha and the balance between the different lymphocyte subsets and an antiangiogenic action. Thalidomide has been used in several cutaneous inflammatory disorders (e.g., erythema nodosum leprosum in lepromatous leprosy, cutaneous lupus erythematosus and severe aphtosis), cancers (e.g., relapsed/refractory multiple myeloma, malignant melanoma and systemic signs in cancer) and inflammatory conditions (e.g., Crohn's disease and rheumatoid arthritis). Several side effects are associated with thalidomide. Some are major, such as teratogenicity, peripheral neuropathy and deep vein thrombosis. Somnolence and rash are frequently reported when thalidomide is used at higher doses as an anticarcinogenic agent and can lead to dose reduction or treatment discontinuation depending on severity. Minor side effects include abdominal pain and endocrine disturbances. To prevent the teratogenicity, use of thalidomide is strictly controlled in western countries with close adherence to a birth control programme. Close monitoring for early development of peripheral neuropathy is also recommended.

Phase I and pharmacokinetic study of thalidomide with carboplatin in children with cancer

PURPOSE

Tumor growth and metastasis is believed to depend on the tumor's ability to induce neovascularization. Recent studies have indicated that thalidomide inhibits angiogenesis. We performed a phase I and pharmacokinetic study of thalidomide with carboplatin in children with refractory solid tumors.

PATIENTS AND METHODS

Carboplatin was administered as a single intravenous dose once every 21 days at a target area under the concentration-time curve of 6 mg/mL.min. Thalidomide was administered daily by mouth. The initial dose level was 100 mg/m(2)/d with intrapatient dose escalation to a maximum dose of 300 mg/m(2)/d. The next cohort of patients started at a dose of 300 mg/m(2)/d, with intrapatient dose escalation to a maximum dose of 500 mg/m(2)/d. Standard response and adverse event criteria were used. Serial blood samples for thalidomide pharmacokinetics studies were obtained after the first dose.

RESULTS

Twenty-two patients received 56 cycles of therapy. The maximum tolerated thalidomide dose was 400 mg/m(2)/d. The dose-limiting toxicity was somnolence. There were no objective responses. Thalidomide's apparent clearance was 55 +/- 16 mL/min/m(2) and the terminal half-life was 5.9 +/- 2.8 hours. There was no evidence of dose-dependent pharmacokinetics in the narrow range studied.

CONCLUSION

Thalidomide at a dose of 400 mg/m(2)/d can be safely administered to children with solid tumors in combination with carboplatin. Somnolence is the major toxicity. In addition, we have characterized the pharmacokinetic behavior of thalidomide in children. This study can serve as the basis for future investigation of thalidomide as an anticancer agent in children.

Clinical Pharmacokinetics of Thalidomide

Thalidomide is a racemic glutamic acid derivative approved in the US for erythema nodosum leprosum, a complication of leprosy. In addition, its use in various inflammatory and oncologic conditions is being investigated. Thalidomide interconverts between the (R)- and (S)-enantiomers in plasma, with protein binding of 55% and 65%, respectively. More than 90% of the absorbed drug is excreted in the urine and faeces within 48 hours. Thalidomide is minimally metabolised by the liver, but is spontaneously hydrolysed into numerous renally excreted products. After a single oral dose of thalidomide 200 mg (as the US-approved capsule formulation) in healthy volunteers, absorption is slow and extensive, resulting in a peak concentration (C(max)) of 1-2 mg/L at 3-4 hours after administration, absorption lag time of 30 minutes, total exposure (AUC( infinity )) of 18 mg. h/L, apparent elimination half-life of 6 hours and apparent systemic clearance of 10 L/h. Thalidomide pharmacokinetics are best described by a one-compartment model with first-order absorption and elimination. Because of the low solubility of the drug in the gastrointestinal tract, thalidomide exhibits absorption rate-limited pharmacokinetics (the 'flip-flop' phenomenon), with its elimination rate being faster than its absorption rate. The apparent elimination half-life of 6 hours therefore represents absorption, not elimination. The 'true' apparent volume of distribution was estimated to be 16L by use of the faster elimination-rate half-life. Multiple doses of thalidomide 200 mg/day over 21 days cause no change in the pharmacokinetics, with a steady-state C(max) (C(ss)(max)) of 1.2 mg/L. Simulation of 400 and 800 mg/day also shows no accumulation, with C(ss)(max) of 3.5 and 6.0 mg/L, respectively. Multiple-dose studies in cancer patients show pharmacokinetics comparable with those in healthy populations at similar dosages. Thalidomide exhibits a dose-proportional increase in AUC at doses from 50 to 400 mg. Because of the low solubility of thalidomide, C(max) is less than proportional to dose, and t(max) is prolonged with increasing dose. Age, sex and smoking have no effect on the pharmacokinetics of thalidomide, and the effect of food is minimal. Thalidomide does not alter the pharmacokinetics of oral contraceptives, and is also unlikely to interact with warfarin and grapefruit juice. Since thalidomide is mainly hydrolysed and passively excreted, its pharmacokinetics are not expected to change in patients with impaired liver or kidney function.

Thalidomide: a review of approved and investigational uses

BACKGROUND

Thalidomide is best known as a major teratogen that caused birth defects in up to 12,000 children in the 1960s. More recently, this agent has been approved by the US Food and Drug Administration for the treatment of erythema nodosum leprosum (ENL) through a restricted-use program. Its immunomodulatory, anti-inflammatory, and antiangiogenic properties are currently under study in a number of clinical conditions.

OBJECTIVE

This article reviews the pharmacology of thalidomide; its approved and off-label uses in dermatologic, oncologic, and gastrointestinal conditions; and adverse events associated with its use.

METHODS

Relevant articles were identified through searches of MEDLINE (1966-June 2002), International Pharmaceutical Abstracts (1970-June 2002), and EMBASE (1990-June 2002). Search terms included but were not limited to thalidomide, pharmacokinetics, pharmacology, therapeutic use, and teratogenicity, as well as terms for specific disease states and adverse events. Further publications were identified from the reference lists of the reviewed articles. Abstracts of recent symposia were obtained from the American Society of Clinical Oncology Web site.

RESULTS

Thalidomide is thought to exert its therapeutic effect through the modulation of cytokines, particularly tumor necrosis factor-alpha. In addition to its approved indication for ENL, thalidomide has been studied in various other conditions, including graft-versus-host disease, discoid lupus erythematosus, sarcoidosis, relapsed/refractory multiple myeloma, Waldenstrom's macroglobulinemia, myelodysplastic syndromes, acute myeloid leukemia, myelofibrosis with myeloid metaplasia, renal cell carcinoma, malignant gliomas, prostate cancer, Kaposi's sarcoma, colorectal carcinoma, oral aphthous ulcers, Behçet's disease, Crohn's disease, and HIV/AIDS-associated wasting. Adverse events most frequently associated with its use include somnolence, constipation, rash, peripheral neuropathy, and thromboembolism.

CONCLUSIONS

Use of thalidomide is limited by toxicity, limited efficacy data, and restricted access. Evidence of its efficacy in conditions other than ENL awaits the results of controlled clinical trials.

Effects of putative hydroxylated thalidomide metabolites on blood vessel density in the chorioallantoic membrane (CAM) assay and on tumor and endothelial cell proliferation

Angiogenesis, in particular anti-angiogenesis, is an area of particular therapeutic interest in cancer treatment. Several anti-angiogenic agents are in the final stages of clinical trials. One of these agents, thalidomide, best known for its teratogenic potential, is showing promise against several tumor types. Thalidomide has been shown previously to require bio-activation to exert its anti-angiogenic effect in isolated blood vessels and endothelial cells. In this work, we confirmed these findings using the in utero chicken embryo chorioallantoic membrane (CAM) system. In particular, the anti-angiogenic effect of thalidomide is significantly enhanced by activation by human but not by rat liver microsomes. We also showed in the CAM assay that hydroxylation of thalidomide at either the 1'- or 5-position retained anti-angiogenic activity whereas its hydroxylation at the 4-position led to an inactive compound. We further demonstrated that thalidomide shows weak anti-proliferative activity against MDA-MB-231 human breast cancer cells in culture. Thalidomide showed slightly more anti-proliferative activity, however, against the SH-SY5Y human neuroblastoma and human umbilical vein endothelial cell (HUVEC) types. Furthermore, incubation of thalidomide with human liver microsomes added no additional anti-proliferative effect in these cell types versus thalidomide given alone. Finally, we report that none of the thalidomide metabolites tested had any anti-proliferative effect against the breast or neuroblastoma cells, but do possess appreciable anti-proliferative activity against the endothelial cells. In summary, this work suggests that hydroxylated thalidomide analogs based on putative metabolites of the drug possess significant anti-angiogenic activity and that exploring further derivatives of these as potential anti-angiogenic agents warrants further merit.

Pharmacokinetics and pharmacodynamics of thalidomide in HIV patients treated for oral aphthous ulcers: ACTG protocol 251. AIDS Clinical Trials Group

Thalidomide has increasing clinical benefits, including the healing of aphthous ulcers in patients with HIV. Unfortunately, pharmacological information addressing the pharmacokinetics (PK) of this compound in HIV patients is limited. Concern exists as to whether thalidomide may alter its own metabolism owing to in vitro data previously reported. Furthermore, no information is available defining the relationship between drug exposure and clinical response. This study evaluated the PK and pharmacodynamics (PD) of thalidomide in patients enrolled in AIDS Clinical Trials Group Protocol 251. Study patients had HIV infection and oral aphthous ulcers of at least 2 weeks'duration. Pharmacologic studies were completed in those subjects randomized to receive active thalidomide at a dose of 200 mg daily for the 4-week study period. PK studies involving serial sampling were carried out in 7 subjects following multiple dosing during study weeks 1 and 4. In addition, trough measurements were done in 20 subjects during each of the 4 study weeks to explore the relationship between time-averaged trough values and extent of clinical response. All samples were analyzed using a validated HPLC method, and parameters were determined using noncompartmental PK analysis. Thalidomide oral clearance averaged 0.14 +/- 0.08 and 0.12 +/- 0.05 l/h/kg on weeks 1 and 4 (p = 0.72), while the terminal elimination half-life averaged 5.7 +/- 1.5 and 7.3 +/- 1.7 hours (p = 0.12). The median time-averaged trough value for subjects deemed complete responders was 0.60, while the median value for noncomplete responders was 0.54. Adjusting for baseline CD4 count and initial index ulcer area, no significant effects were observed of increased thalidomide levels on response. In summary, this study provides steady-state PK data in HIV patients managed with thalidomide and suggests negligible effect of chronic dosing on drug clearance (comparing results from weeks 1 and 4). Furthermore, variable trough measurements between patients do not directly influence the effectiveness of thalidomide for oral aphthous ulcers.

Thalidomide: dual benefits in palliative medicine and oncology

Thalidomide is an immunomodulator, anti-angiogenic agent, anti-cytokine, and anti-integrin. Alone or in combination with other drugs, thalidomide has also demonstrated anti-cachexin and anti-neoplastic properties. Anorexia and cachexia are common symptoms of advanced cancer. Since certain cytokines also promote tumor growth, we may have a class of agents with palliative and anti-tumor benefits in combination with anti-neoplastics and anti-cytokines, such as thalidomide.

Thalidomide dose proportionality assessment following single doses to healthy subjects

Thalidomide is approved in the United States for treating erythema nodosum leprosum, a complication of leprosy. The present study determined the single-dose oral pharmacokinetics and dose proportionality from 50 to 400 mg of Celgene's commercial Thalomid thalidomide formulation in an open-label, single-dose, three-way crossover study. Fifteen healthy subjects were given 50, 200, and 400 mg of thalidomide on three occasions, and blood samples were collected over 48 hours. Pharmacokinetic parameters were determined using noncompartmental methods, and dose proportionality was assessed by linear regression of dose-normalized Cmax and AUC0-infinity. No serious or unexpected adverse events occurred. The most common adverse events were dizziness, somnolence, headache, and nausea. One patient was discontinued because of pharyngitis. There was a significant deviation from proportionality for Cmax with increases being less than proportional than changes in dose. AUC0-infinity increased proportionally with dose, suggesting that the overall amount of thalidomide absorbed, as well as its clearance, is independent of dose over the range used. V/F was found to increase with dose. This was most likely due to the terminal rate constant, which is used to calculate V/F, actually representing the absorption process rather than elimination (i.e., flip-flop phenomenon). The terminal rate constant (absorption rate constant) for the highest dose was 50% less than for the other two lower doses. The less than proportional increases in Cmax were most likely due to thalidomide's low aqueous solubility. Thalidomide shows reasonable dose proportionality with respect to AUC from 50 to 400 mg.

Thalomid (Thalidomide) capsules: a review of the first 18 months of spontaneous postmarketing adverse event surveillance, including off-label prescribing

The sedative/hypnotic thalidomide was withdrawn from the worldwide market nearly 40 years ago, because of its teratogenic and neurotoxic effects. Thalidomide was later found to very effectively suppress erythema nodosum leprosum (ENL). The US Food and Drug Administration (FDA) has approved Thalomid (thalidomide) capsules for the acute treatment of the cutaneous manifestations of moderate to severe ENL. Thalidomide is currently under investigation for the treatment of a wide variety of diseases, including conditions thought to have an inflammatory or immune basis, malignancies and complications of infection with HIV. Interest in the potential anti-inflammatory, immunomodulatory and anti- angiogenic effects of thalidomide has resulted in off-label use of prescription thalidomide. During the first 18 months of spontaneous postmarketing adverse event surveillance for Thalomid, 1210 spontaneous postmarketing adverse event reports were received for patients treated with prescription thalidomide for all therapeutic indications, including off-label use. The most common adverse events spontaneously reported would have been expected on the basis of the current Thalomid labelling/product information. The current labelling/product information reflects what was known about the risks associated with thalidomide therapy in limited patient populations at the time of the approval of Thalomid. With the postmarketing use of thalidomide in populations other than patients with ENL, it becomes increasingly important to identify patient groups that may be particularly susceptible to specific adverse drug effects and to identify conditions under which specific adverse events may be more likely to occur. Oncology patients may represent a patient population with increased susceptibility to thalidomide-associated adverse effects, including thromboembolic events. Consideration of the spontaneous postmarketing safety surveillance data may help to identify and characterise factors associated with increased risk in this and other patient groups. Serious unexpected adverse events reported with sufficient frequency to signal previously undetected product-event associations for which there may potentially be plausible evidence to suggest a causal relationship have included seizures and Stevens-Johnson syndrome. The potential effects of thalidomide on wound healing are also being closely monitored. Premarketing human clinical trials of drug products are inherently limited in their ability to detect adverse events. Broader postmarketing experience with thalidomide in more varied patient populations and more experience in the setting of long term thalidomide use will increase our ability to detect rare adverse events and to identify signals that may need to be evaluated in more controlled settings.

Intravenous formulations of the enantiomers of thalidomide: pharmacokinetic and initial pharmacodynamic characterization in man

Thalidomide, a racemate, is coming into clinical use as an immunomodulating and antiinflammatory drug. These effects may chiefly be exerted by S-thalidomide, but the enantiomers are interconverted in-vivo. Thalidomide is given orally, although parenteral administration would be desirable in some clinical situations. The aim of this study was to prepare solutions of the enantiomers of thalidomide for intravenous administration and to investigate their pharmacokinetics and sedative effects following infusion in man. Solubility and stability of the enantiomers in 5% glucose solution was investigated. After a dose-determination experiment in one subject, six healthy male volunteers received R- and S-thalidomide separately by 1-h infusions in a randomized double-blind cross-over study. Blood was sampled over 22h and sedative effects were recorded. Blood concentrations of the enantiomers were determined by stereospecific HPLC. A four-compartment model consisting of a two-compartment model for each enantiomer, with elimination from both compartments, connected by rate constants for chiral inversion was fitted to the concentration data, while the sedative effects were correlated with the blood concentrations of R- and S-thalidomide by means of logistic regression. The enantiomers of thalidomide were chemically stable in solution for at least a week at room temperature. The infusions were well tolerated. Sedation, which was the only observed effect, was related to the blood concentration of R-thalidomide. Inter-individual variation in the disposition of the enantiomers was modest (e.g. terminal half-lives ranged between 3.9 and 5.3h). Pharmacokinetic modelling predicted that varying the infusion time of a fixed dose of S-thalidomide between 10 min and 6h would have little influence on the maximal blood concentration of formed R-thalidomide. To our knowledge this is the first time that thalidomide has been administered intravenously.