By Q. Lukar. Saint Thomas University. 2019.
The beam is scanned across the sample in the horizontal plane with one or more (servo-controlled) oscillating mirrors buy bimat 3 ml without a prescription symptoms in early pregnancy. This scan- ning method usually has low reaction latency and the scan speed can be varied bimat 3 ml fast delivery symptoms ms women. Slower scans provide a better signal-to-noise ratio buy 3ml bimat amex medicine vicodin, resulting in better contrast and higher resolution cheap bimat 3ml free shipping medications and grapefruit juice. Information can be collected from different focal planes by raising or lowering the microscope stage. The computer can generate a three-dimensional picture of a specimen by assembling a stack of these two-dimensional images from successive focal planes (7). The difference between the ﬂuorescence and absorption wavelengths is called the Stokes shift. If the Stokes shift is sufﬁciently large, the exciting and ﬂuorescence signals can be efﬁciently sep- arated by ﬁlters, so that only the ﬂuorescence light would reach the detector. If the specimen is heterogeneous, the concentration of the ﬂuorescent probe is coordinate dependent, which results in a high-contrast image. The illuminated voxel is a diffraction-limited spot within the specimen pro- duced by a focused laser beam. Fluorescence light passes through the pinhole aper- ture located in the focal plane that is conjugate to the illuminated point of the spec- imen. The signal that reaches the detector from the regions above and below the voxel is of much weaker intensity since the corresponding beams diverge and cover an area much larger than the area of the pinhole. Under a microscope, the thin tissue section is viewed through the glass slide on which it is mounted and microscopic clusters of cells are selected for isolation. When the cells of choice are in the center of the ﬁeld of view, the operator pushes a button that activates a near infrared laser diode integral with the microscope optics. The pulsed laser beam activates a precise 174 Murthy and Pathak spot on the transfer ﬁlm, fusing the ﬁlm with the underlying cells of choice. The transfer ﬁlm with the bonded cells is then lifted off the thin tissue section, leaving all unwanted cells behind. It can be performed on a variety of tissue samples, including blood smears, cytologic preparations (10), cell cultures, and aliquots of solid tissue. The concentration of endotoxin in a sample is in direct proportion with absorbance and is calculated from a standard curve. Add 100 L of prewarmed substrate solution and incubate at a nominal temperature of 37 ± 1◦C for another 6 min- utes. Add 100 L of the stop solution to the samples in the microplate and read absorbance at 405 nm. Assay Acceptance Criteria Linear regression algorithm is used to build standard curves. At least three calibration standards should be available in order for assay to In Vitro Characterization of Nanoparticle Cellular Interaction 175 be considered acceptable. If quality control measures fail to meet the acceptance criterion, runs should be repeated. If sample interference is detected, then analysis of diluted sample should be performed. For parenteral drugs administered intrathecally, limit is equal to K/M, that is, 0. The nanoparticle formulations will be treated as devices for accep- tance/rejection, unless data for K/M formula are available. The protocol includes tests for yeast, mold, and bacteria using Millipore sampler devices. Remove the sampler from its plastic bag under sterile conditions, and then remove a paddle from case and apply 1 mL of nanoparticle preparation or dilution onto the surface of a ﬁlter. When these detection complexes were bound to bacteria or a speciﬁc peptide, a measurable change in acceptor emission was observed owing to change in the three-dimensional conformation of the antibody. Fiber optic biosensors measure conformational changes occurring when anti- bodies bind antigens, and thus provide a viable detection method for mycoplasmas. Fluorescence microscopy method of detection of Mycoplasma was described in a protocol developed by Darlington (16). This technique provides a valuable resource for researchers wishing to go beyond a basic description of cellu- lar uptake to characterize intracellular trafﬁcking and targeting in greater depth. In addition to identifying cellular compartments accessed by agents and delivery vehi- cles, it is also important to understand the kinetics of their transport within complex biological environments, both extracellular and intracellular. In recent years, there have been signiﬁcant advances in the understanding of these transport processes facilitated by time-lapse imaging and associated computational analyses. Cell Binding and Transfection Studies Confocal microscopy is a powerful tool to study cell binding and intracellular trafﬁcking in understanding drug targeting and biochemical screening in drug development. Fluorescence methods are commonly used to assay the binding of drug-like compounds to signaling proteins and other bioparticles. Highly sensi- tive measurements within nanometer-sized, open-probe volumes can be achieved by confocal epi-illumination including ﬂuorescence correlation spectroscopy and its related techniques. A typical biochemical application of ﬂuorescence correlation spectroscopy is a ligand-binding assay. Ligand-Binding Studies One of the most powerful tools for receptor research and drug discovery is the use of receptor–ligand afﬁnity screening. The methods adopted earlier involved the use of radioactive ligands to identify a binding event; however, there are numerous limitations involved in the use of radioactivity. All reactions were performed in 96-well, V-bottom polypropylene plates for 2 hours at room temperature. Reactions were terminated by rapid ﬁltration of the binding reaction (50 L) through AcroWell ﬁlter plates, followed by three ﬁltration washes with 300 L of hypotonic buffer. Enhancement solution (150 E L/well) was added to each well and time-resolved ﬂuorescence signal was quantiﬁed. Saturation binding experiments can also be performed with 125I-labeled galanin in 60 L of hypotonic buffer supplemented with 0. After incubation for 2 hours at room temperature, binding reactions were transferred (50 L) to a 96-well harvest plate, harvested, and washed with hypo- tonic buffer (3 × 300 L). Wells were resuspended with 50 L of Optiphase r Super- c mix and counted on a Trilux 1450 MicroBeta (PerkinElmer Wallac). In Vitro Cell Transfection Studies Transfection describes the introduction of foreign material into eukaryotic cells with a virus vector or other means of transfer. The term “transfection” for nonviral meth- ods is most often used in reference to mammalian cells. Transfection of animal cells typically involves opening transient pores or “holes” in the cell plasma membrane, to allow the uptake of material. In addition to electroporation, transfection can be carried out by mixing a cationic lipid with the material to produce liposomes, which fuse with the cell plasma membrane and deposit their cargo inside. Many materials have been used as carriers for transfection, which can be divided into three kinds: (cationic) polymers, liposomes, and nanoparticles. One of the eco- nomical methods is transfection by calcium phosphate, originally discovered by Graham and colleagues in 1973 (19,20). The suspension of the precipitate is then added to the cells to be transfected (usually a cell culture grown in a mono- layer). Another method is the use of cationic polymers such as diethylaminoethyl–dextran or polyethylenimine. For eukaryotic cells, lipid cation–based transfection is more typically used because the cells are more sensitive.
Platelet transfusions Platelet transfusions are only indicated in acute active bleeding uncontrolled by other means or before procedures safe bimat 3 ml treatment quadratus lumborum. In an adult order 3ml bimat with visa treatment yeast infection, 1 mega-unit of single donor order 3 ml bimat amex treatment 0f osteoporosis, leucocyte depleted platelets is usually sufficient to control the bleeding initially buy 3ml bimat amex treatment neuroleptic malignant syndrome. Platelet transfusions have limited benefit in this condition as platelets are rapidly destroyed by the immune system. This condition presents with: » anaemia, » thrombocytopenia, often with purpura but not usually severe bleeding, » acute renal insufficiency that may be associated with anuria and may require acute dialysis, » neurologic abnormalities, and » fever. If the patient is bleeding, replace haemostatic factors with cryoprecipitate or fresh frozen plasma. If the patient is not actively bleeding and platelet count > 20 000, then platelet transfusion is not necessary. Replacement therapy for thrombocytopenia should consist of 1 apheresis single donor unit / megaunit (expected platelet count increment 30–50 x 9 9 10 /L) or 6 random donor units (expected increment 50–60 x 10 /L), ideally 9 aiming to raise the platelet count > 50 x 10 /L. Perform frequent estimation of the platelet count and coagulation screening tests. Differential diagnosis include: » cellulitis, » superficial thrombophlebitis, » chronic venous insufficiency, » lymphoedema, » popliteal (Baker’s) cyst, » internal derangement of the knee, and » calf muscle pull or tear Diagnosis is primarily clinical and confirmed with imaging studies, e. Ultrasonography should be repeated after a week but may be omitted if D-dimer is negative. Units of unfractionated heparin Volume of heparin in mL (25 000 units/mL) Weight (kg) Loading 12 hourly Loading 12 hourly dose dose (units) dose dose (units) (mL) (mL) 35 kg 11 000 units 8 750 units 0. Thrombolytic therapy is indicated only in patients with angiographically confirmed early pulmonary embolism where haemodynamic stability cannot be achieved. Although the risk of bleeding is small, in the following patients prophylaxis should only be used under exceptional circumstances: » active bleeding, » intraocular, intracranial or spinal surgery, » lumbar puncture or epidural anaesthesia within 12 hours, » renal insufficiency, » coagulopathy, or » uncontrolled hypertension. Heparin induced thrombocytopenia A severe immune-mediated drug reaction occurring in 1–5% of patients receiving heparin (unfractionated or low molecular weight heparin) therapy. Diagnosis needs a high index of suspicion and should be considered if a patient has a 50% drop in platelet count within 5–10 days after initiating heparin therapy. Volume of diluent Glyceryl trinitrate Concentration of 5mg/mL dilution 5 mL (25 mg) 100 mcg/mL 250 mL 10 mL (50 mg) 200 mcg/mL 20 mL (100 mg) 400 mcg/mL 10 mL (50 mg) 100 mcg/mL 500 mL 20 mL (100 mg) 200 mcg/mL 40 mL (200 mg) 400 mcg/mL Solution 100 mcg/mL 200 mcg/mL 400 mcg/mL Concentration solution solution solution (mcg/mL) Dose (mcg/min) Flow rate (microdrops/min = mL/hour) 5 3 — — 10 6 3 — 15 9 — — 20 12 6 3 30 18 9 — 40 24 12 6 60 36 18 9 80 48 24 12 100 60 30 15 120 72 36 18 160 96 48 24 200 – 60 30 When clinically stable without signs of heart failure, hypotension, bradydysrhythmias or asthma: -blocker, e. Unstable angina pectoris: Chest pain that is increasing in frequency and or severity, or occurring at rest. Volume of diluent Glyceryl trinitrate Concentration of 5mg/mL dilution 5 mL (25 mg) 100 mcg/mL 250 mL 10 mL (50 mg) 200 mcg/mL 20 mL (100 mg) 400 mcg/mL 10 mL (50 mg) 100 mcg/mL 500 mL 20 mL (100 mg) 200 mcg/mL 40 mL (200 mg) 400 mcg/mL Solution 100 mcg/mL 200 mcg/mL 400 mcg/mL Concentration solution solution solution (mcg/mL) Dose (mcg/min) Flow rate (microdrops/min = mL/hour) 5 3 — — 10 6 3 — 15 9 — — 20 12 6 3 30 18 9 — 40 24 12 6 60 36 18 9 80 48 24 12 100 60 30 15 120 72 36 18 160 96 48 24 200 – 60 30 3. If ß-blocker cannot be tolerated or is contraindicated, consider long acting calcium channel blocker. Patients under the age of 65 with no heart diseases or other risk factors may be managed with aspirin alone. Risk factors of stroke in atrial fibrillation are: » cardiac failure, » hypertension, » age > 65, » diabetes, and » stroke. If not controlled on those agents, refer to specialist for consideration of alternative therapy, e. Long-term therapy Continue warfarin anticoagulation long-term, unless contra-indicated: • Warfarin, oral, 5 mg daily. If not controlled on these agents, refer to specialist for consideration of alternative. Vagal stimulation might slow the ventricular rate and make the dysrhythmia more obvious. If flutter has been present longer than 48 hours, defer cardioversion until after 4 weeks’ anticoagulation with warfarin, unless severe symptoms or heart failure require urgent cardioversion. Do not use verapamil as it will not convert flutter to sinus rhythm and may cause serious hypotension. Long-term therapy Recurrent atrial flutter is an indication for referral as some may be cured by radio-frequency catheter ablation. The patient should be supine and as relaxed as possible, to avoid competing sympathetic reflexes. If the drug reaches the central circulation before it is broken down the patient will experience flushing, sometimes chest pain, wheezing and anxiety. If the tachycardia fails to terminate without the patient experiencing those symptoms, the drug did not reach the heart. Lidocaine will only terminate ± 30% of sustained ventricular tachycardias, and may cause hypotension, heart block or convulsions. Verapamil and digoxin may precipitate ventricular fibrillation by increasing the ventricular rate. In acute myocardial infarction, treat non-sustained ventricular tachycardia only if it causes significant haemodynamic compromise. Lidocaine will only terminate ± 30% of sustained ventricular tachycardias, and may cause hypotension, heart block or convulsions. Torsades complicating bradycardia: • Adrenaline infusion to raise heart rate to > 100/ minute (if temporary pacing unavailable). The condition may also be induced by metabolic and electrolyte disturbances, as well as by certain medicines. External pacemaker should be available in all secondary hospitals and must be preceded by appropriate analgesia. Potentially reversible causes include: » anaemia, » thiamine deficiency, » thyroid disease, » ischaemic heart disease, » valvular heart disease, » haemochromatosis, and » constrictive pericarditis. Significant volume overload or abnormal renal or hepatic function, loop diuretic: • Furosemide, oral, daily. They should be used short term only, to correct documented low serum potassium level. Patients should not be fluid overloaded or have low blood pressure before initiation of therapy. Early surgical intervention in acute fulminant and prosthetic valve endocarditis is often indicated. Antibiotic therapy It is essential to do at least three and no more than six blood cultures taken by separate venipunctures before starting antibiotics. In patients with subacute presentation and no haemodynamic compromise, wait for the results before starting antibiotics. Empiric treatment is indicated in patients with a rapidly fulminant course or with severe disease only. Duration of therapy given is the minimum and may be extended based on the response (clinical and laboratory). Six weeks of therapy may be required in cases (nutritionally with a history of > 3 months, or mitral or prosthetic variant valve involvement. In the rare occurrence of a penicillin sensitive staphylococcus, penicillin should be used in preference to cloxacillin. Endocarditis prophylaxis Cardiac conditions Patients with the following cardiac conditions are at risk of developing infective endocarditis: » Acquired valvular heart disease with stenosis or regurgitation. Procedures requiring prophylaxis Antibiotic prophylaxis is recommended for all dental procedures that involve manipulation of either the gingival tissue or the peri-apical region of the teeth. Antibiotic prophylaxis is not recommended for patients who undergo a gastro-intestinal or genito-urinary procedure. Refer all patients to a dental clinic/dental therapist for assessment and on- going dental care. It further commented that because the antibiotic is not without risk, there is a potential for a greater mortality from severe hypersensitivity than from withholding antibiotics.
The high demand and erratic supply of drugs discount 3 ml bimat overnight delivery medicine 2632, weak regulatory systems generic bimat 3ml mastercard 4 medications list, and un- even awareness contribute to the trade in both falsifed and substandard drugs cheap bimat 3 ml line medications 2355. Medicines are what economists describe as an inelastic good; changes in the unit price of the medicine have proportionately little effect on the demand generic bimat 3ml free shipping lb 95 medications. Price inelasticity, combined with a high relative price, make medi- cines a major expense for patients around the world. Drug shortages drive up the price of medicines and push consumers to unregulated markets. Reducing the costs and increasing the availability of medicines would help prevent drug scarcity. For generic manufacturers, companies that generally run on low margins, the costs of proving bio- equivalence and preparing a manufacturer’s dossier for regulatory review can be prohibitive to market entry. Different regulatory authorities have different, often widely divergent, requirements. To complicate the problem, many small regulatory authorities lack the technical depth to evaluate the bioequivalence data that generics manufacturers submit. The high cost of market authorization impedes the development of a strong generics industry in poor countries. A more robust generic drug mar- ket could help prevent the drug shortages and price spikes that encourage the sale of poor-quality products. Regulatory authorities can work to better harmonize their procedures, thereby improving their own effciency and reducing barriers to market entry for good-quality generics manufacturers. The use of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use Com- mon Technical Document format for registration would ease the regulatory burden on generics companies. Regulators also reap a spillover beneft of more convergent regulatory systems without negotiating cumbersome mu- tual recognition agreements. Recommendation 4-3: Regulatory authorities in low- and middle- income countries should use the International Conference on Harmoni- sation Common Technical Document format for product registration to better harmonize their procedures and reduce application costs for manufacturers. To the same end, they should also conduct joint inspec- tions and use a common inspection report. A functioning medicines regulatory authority is a necessary condition for a robust generic medicines market. Strengthening the drugs regulatory system, building the inspectorate, enforcing quality standards, and licensing in accordance with international standards are es- sential to improving drug quality. Without a competent regulatory authority to inspect wholesalers, distributors, and manufacturers, opportunities to corrupt the drug supply abound. A strategy for compliance with international standards can help reduce redundant work and fragmentation. Both industry and regulators should agree to work toward the priorities identifed in the strategic plan, an openly shared document. Recommendation 4-4: Governments in low- and middle-income coun- tries should support their regulatory agencies to develop strategic plans for compliance with international manufacturing and quality-control standards. In the least developed countries, international organizations should support their efforts. Large pharmaceutical manufacturing nations such as India and China suffer from fragmented regulatory systems and an unclear division of re- sponsibilities between state and national governments. The United States has similar problems, evidenced by the recent fungal meningitis outbreak brought on by a contaminated injectable steroid drug, compounded under unhygienic conditions at the New England Compounding Center. Similar confusion causes regulatory gaps in other countries where national and local governments share responsibilities for drug regulation. During times of crisis, such as the meningitis outbreak, public inter- est in drug quality peaks, but it can be diffcult to maintain. They may not realize the risks of circumventing the regulated distribution system. In poor countries, patients are often more aware of the problem, but there are knowledge gaps, especially among the poorest and least educated. Effective communication campaigns can raise awareness of the problem and give consumers empowering messages on how to protect themselves. Targeted health worker education on falsifed and substandard medi- cines would improve understanding of the problem around the world. This education should emphasize the correct reporting channels health workers can use to confrm suspected cases of bad drugs. Illegitimate drugs are a potential threat in all countries, though risk varies widely from country to country. An effective communication campaign should present accurate information in a way that empowers patients to protect their health. Final formula- tions are then exported, and packaging, repackaging, and sale can happen in many other countries. Drugs change hands many times between the manufacturer and patient; every transaction is an opportunity for falsifed and substandard products to infltrate the market. Drug quality around the world could be improved with changes to the drug distribution system. The systems differ markedly between developed and developing coun- tries, however. Fewer, larger frms control manufacture and the wholesale drug markets in developed countries, where most patients get medicines from licensed pharmacies or dispensaries. In low- and middle-income coun- tries, multiple parallel distribution systems of varying effciency run in the same country. It is also diffcult and expensive to transport medicines over poor roads to remote villages, as supply chain managers in poor countries must do. There are two kinds of drug wholesalers: primary wholesalers who have written distribution contracts with manufacturers and buy directly from them, and secondary wholesalers who buy from other intermediaries. When they see that a medicine is scarce in one region, they can buy the same medicine from other wholesalers that may be fush with it. Wholesalers may repackage products repeatedly, and in the repackaging fake products can gain authentic labels. In the United States, thousands of secondary wholesalers trade medi- cines, causing drug shortages and exploiting them for proft. And, because the wholesale trade is national, weak- nesses in one state’s system can become vulnerabilities in another. Recommendation 5-1: State licensing boards should only license whole- salers and distributors that meet the National Association of Boards of Pharmacy accreditation standards. Food and Drug Adminis- tration, in collaboration with state licensing boards, should establish a public database to share information on suspended and revoked wholesale licenses. Similar weaknesses plague the wholesale system in developing coun- tries, and action in the American market might give regulators around the world example and encouragement to tighten controls on the chaotic wholesale market. More stringent licensing requirements can improve the wholesale sys- tem, but drugs will still need to move from factory to the vendor, passing through many hands before reaching the patient. With every transaction on the chain, there is a risk of the drug supply being compromised. Crimi- nals take advantage of places where the distribution chain breaks down and medicines depart from the documented chain of custody. Drugs that leave the proper distribution system are called diverted drugs; the markets that trade diverted drugs or, more generally, markets that trade with little authorized oversight are called gray markets. Drug diversion is the means through which medicines approved for sale in one country are sold in others, where they may not be registered. Small thefts and large heists compromise the integrity of the drug distribution chain and confdence in the quality of medicines. In rich and poor countries alike, drugs often circulate outside of the main distribution channels with- out a drug pedigree, a record of a drug’s every sale and owner. Drug pedigrees depend on attaching some form of unique identifying numbers to products.
The bioavailability from an oral capsule is about 50% bimat 3ml generic professional english medicine, but there is evidence that the bioavailability is dose-dependent cheap bimat 3 ml without prescription symptoms mercury poisoning, with decreasing absorption of doses > 200 mg (Harvey et al bimat 3 ml overnight delivery symptoms yellow fever. In one study 3 ml bimat with amex treatment wetlands, the bioavailability of a 100-mg dose was 76%, while that of a 400-mg dose was 48% (p < 0. This effect might be related to a concentration-dependent reduction in the solubility of etoposide in the stomach and small intestine (Joel et al. The bioavailability of etoposide varies widely among and within patients (Harvey et al. Little etoposide penetrates into other fluid spaces, almost certainly because of its extensive protein binding. The concentrations of etoposide in cerebrospinal fluid were only 1–2% of the plasma concentration after high doses (Hande et al. After administration of a high dose, the peak concentrations in ascites and pleural fluid were considerably lower than the peak plasma concentration, but at later times (> 10 h) the concentrations were higher than in plasma, suggesting slow clearance from these fluid compartments (Hande et al. Because etoposide is excreted renally, clearance is reduced in patients with impaired renal function (Arbuck et al. Changes in the pharmacokinetics of etoposide are more subtle in patients with impaired liver function. While the pharmacokinetics of total plasma etoposide may be unchanged, a reduction in protein binding has been reported in these patients, which is associated with decreased serum albumin and/or increased serum bilirubin (Stewart et al. This increase in free etoposide is asso- ciated with greater toxicity in this group of patients (Joel et al. Etoposide is administered as the trans-lactone (ring furthest to the right, Figure 1), but cis-etoposide can also be detected in human urine (Holthuis et al. This might be a storage phenomenon, since isomerization sometimes occurs during freezing of plasma samples under slightly basic conditions (Rideout et al. Although urinary glucuronide and/or sulfate conjugates were reported to account for 5–22% of an intravenous dose of etoposide (D’Incalci et al. Etoposide glucuronide in the urine of treated patients accounted for 8–17% of a dose of 0. In patients with renal or liver impairment given somewhat lower doses of 70–150 mg/m2, 3–17% of the dose was excreted in the urine within 72 h as etoposide glucuronide (D’Incalci et al. These findings are in broad agreement with those of early studies in which [3H]eto- poside was used, which indicated that 35–66% of the administered dose of radiolabel was recovered in the urine (Allen & Creaven, 1975). Less than 4% of a dose was recovered in the bile after 48 h in patients with biliary drainage tubes (Arbuck et al. The faecal recovery of radiolabel after intravenous administration of [3H]etoposide (130– 290 mg/m2) was variable, representing 0–16% of dose, but the collections were known to be incomplete because of faecal retention and other difficulties associated with the poor general condition of many of the patients (Creaven & Allen, 1975). In a study reported as an abstract in four patients with small-cell lung cancer given [14C-gluco- pyranoside]etoposide, 56% of the radiolabel was recovered in urine and 44% in faeces over five days, for a total recovery of 100 ± 6% (Joel et al. Studies in lung cancer patients have shown that the plasma concentrations asso- ciated with haematological toxicity are higher than those required for antitumour ac- tivity. The plasma concentration associated with antitumour activity may be different for different tumour types (Minami et al. The pharmacokinetics of etoposide is influenced by concurrent administration of a number of other drugs: clearance may be increased by phenytoin (Mross et al. Rhesus monkeys given [3H]etoposide showed biphasic elimination, with a distri- bution phase half-time of about 1. Biphasic elimi- nation was also observed in mice, with a distribution half-time of 1. The clearance rate was 17 mL/kg bw per min, and the distri- bution volume was 820 mL/kg bw (Colombo et al. The total plasma clearance rate (342–435 mL/min per m2) and the distribution volume (22–27 L/m2) were not dose-dependent. The peak plasma concentration occurred at the end of the infusion of etoposide phosphate, indi- cating rapid conversion of the pro-drug to etoposide (Igwemezie et al. Thirty minutes after intravenous administration of etoposide to rats, the highest concentrations were found in the liver, kidneys and small intestine. By 24 h after the dose, the tissue concentrations were negligible (Achterrath et al. In leukaemic cells, the uptake appeared to be linear up to 5 min and reached a steady state by 20–30 min (Allen, 1978; Colombo et al. After removal of the drug, an exponential efflux with a half-time of just 3 min was observed (Allen, 1978). At the same extracellular concentration, the intracellular concentrations of eto- poside were 15–20 times lower than those of the closely related drug teniposide (Allen, 1978; Colombo et al. In rat liver homogenates, liver microsomes and in rats in vivo, etoposide was exten- sively metabolized to only one major metabolite, which was not formally identified (van Maanen et al. In perfused isolated rat liver incubated with etoposide, the total recovery in bile was 60–85%, with roughly equal amounts of etoposide and two glucuronide metabolites (Colombo et al. After intravenous injection of [3H]etoposide to rabbits, the total urinary excretion of radiolabel was 30% after five days, with very little thereafter. A single glucuronide metabolite was identified in rabbit urine, which was present in larger amounts than etoposide. A number of authors have reported the peroxidase-mediated oxidation of etoposide to a phenoxy radical, with further oxidation to the ortho-quinone, semi-quinone and catechol derivatives (Broggini et al. Cytochrome P450-mediated demethylation directly to the catechol has also been reported (van Maanen et al. It remains unclear how much these reactive metabolites contribute to the cytotoxic or mutagenic activity of etoposide. The main, dose-limiting toxic effect is myelosuppression, manifest principally as leukopenia. After standard intravenous doses (375–500 mg/m2 total dose) of etoposide administered alone over three to five days, 20–50% of previously untreated patients experienced moderate to severe leukopenia or neutropenia, typically occurring around day 10–12, with recovery by day 21. Nausea and vomiting are gener- ally mild but may be more common after oral administration. Mucositis can occur at standard doses, when it is generally mild, but at high doses (< 3500 mg/m2), mucositis can become dose-limiting (Postmus et al. Hypersensitivity reactions to etoposide have been reported but are uncommon (O’ Dwyer & Weiss, 1984). In eight patients reported to the Investigational Drug Branch of the National Cancer Institute between January 1982 and May 1983, these reactions included flushing, respiratory problems, changes in blood pressure and abdominal pain, often occurring soon after the start of drug administration and generally resolving rapidly when the infusion was stopped. These reactions are less common with etoposide than with the related drug teniposide and have not been reported after oral administration, suggesting that other agents in the formulation may be at least partly responsible. The very low incidence of reported cases may reflect only serious hyper- sensitivity reactions (Weiss, 1992), as mild reactions were found in 51% of patients receiving etoposide as part of combination chemotherapy for Hodgkin disease (Hudson et al. Most patients can be successfully re-treated with etoposide after a premedication comprising antihistamine and/or corticosteroids (Hudson et al. Cardiotoxicity was reported in three of eight patients with pre-existing cardiac disease who received etoposide by infusion (Aisner et al. Four-week studies of toxicity were conducted in rats treated intraperitoneally at 0. At the highest doses, the main toxic effect was myelosuppression, with anaemia, leukopenia and thrombocytopenia, and some hepatotoxicity. Pathological changes were noted in the lung in rats, and mild enteritis was seen in dogs.