Measurement of artemisinin and its derivatives in biological fluids

The development of selective analytical methods for the determination of artemisinin and its analogues and metabolites in biological fluids poses challenging problems. All are thermally labile, lack ultraviolet (u.v.) absorbent or fluorescent chromophores and do not possess functional groups for derivatization. Two chemical approaches have been used; acid (or alkali) catalysed decomposition to u.v. absorbing compounds followed by high-performance liquid chromatography (HPLC) of the decomposition products, and HPLC with reductive electrochemical detection. Each has its difficulties. The first, although sensitive, may lack specificity if drug metabolities are also converted to identical products, but a recently developed method surmounts this problem. The second, while providing good sensitivity and specificity, requires rigorous deoxygenation of the sample and mobile phase and an electrochemical detector, which is expensive, and may prove difficult to operate under field conditions. As an alternative to a chemical method, a bioassay may be suitable for plasma level monitoring in such circumstances. However its lack of selectivity means it is of questionable value in the determination of the pharmacokinetic parameters for individual drug-related species.

D.L. Davies and 'Normal drinking in recovered alcohol addicts': the genesis of a paper

This paper explores the genesis of D.L. Davie's 1962 paper on 'Normal drinking in recovered alcohol addicts' in terms of the background and training of its author and the institutional context within which he worked. Davies was born in 1911 and died in 1982. Alter a brilliant undergraduate medical career and war service in command of a military hospital, Davies joined the staff of the Maudsley Hospital in 1946 and was exposed to the intellectual influence of Aubrey Lewis. The research tradition to which he was introduced emphasised case description. The 1962 paper radically challenged perceived wisdom by purporting to describe 7 'alcohol addicts' who had achieved sustained, controlled drinking over a 7-11 year period. A subsequent follow-up of these cases suggested that Davies had been substantially mislead, and the paradox exists that a widely influential paper which did much to stimulate new thinking was based on faulty data. Some possible explanations for the occurrence of such a scientific accident are considered and the relevance of this story for the present day.

Effect of malaria infection on the pharmacokinetics of paracetamol in rat

1. Paracetamol (P; 50 and 300 mg/kg i.v.) was administered to the control and malaria-infected (MI) male Wistar rat in order to assess the effect of MI on the metabolism of paracetamol to its glucuronide (PG) and sulphate (PS) conjugates and their excretion in urine. 2. At a dose of 50 mg/kg, neither total clearance (ClT) (controls, 20.3 +/- 0.5; MI, 19.9 +/- 0.9, ml/min/kg; mean +/- SD, p > 0.05) nor the renal clearance of P (ClR) were affected by MI. Although the formation clearance of PG (Clf PG) was decreased by about 40% (controls, 6.6 +/- 1.1; MI, 3.9 +/- 0.9, ml/min/kg, p < 0.05), the formation clearance of PS (Clf PS) was increased by 30% in the MI rat (controls, 8.8 +/- 0.9; MI, 11.2 +/- 1.7, ml/min/kg, p < 0.05), and therefore Clm (controls, 19.7 +/- 0.5; MI, 19.2 +/- 0.8, ml/min/kg, p > 0.05) was unchanged by MI. 3. At a dose of 300 mg/kg, MI produced a significant decrease in the total clearance of P (ClT) (controls, 16.9 +/- 1.0; MI, 11.9 +/- 0.9, ml/min/kg, p < 0.05), metabolic clearance (Clm) (controls, 15.9 +/- 1.4; MI, 11.3 +/- 0.9, ml/min/kg, p < 0.05) and the formation clearance of PG (Clf PG) (controls, 7.9 +/- 1.3; MI, 4.7 +/- 1.5, ml/min/kg, p < 0.05) without affecting Clf PS and ClR of P. 4. These findings indicate that MI impairs the glucuronidation of paracetamol in rat in vivo at both the low and high doses of P. Increased sulphate formation appeared to compensate for decreased glucuronidation at the lower dose.(ABSTRACT TRUNCATED AT 250 WORDS)

A test of the matching hypothesis: alcohol dependence, intensity of treatment, and 12-month outcome

The "matching hypothesis"--the concept that treatment will be improved if matched to individual needs or characteristics--has, over recent years, attracted attention, and some research to test its validity has been conducted. These studies are briefly reviewed and an analysis then reported which focuses on exploration of the possible interaction between treatment intensity, patient characteristics with particular reference to degree of dependence on alcohol, and 12-month treatment outcome. The data derive from a controlled trial in which patients were randomized between "Treatment" and "Advice". No significant interactions of the kind postulated were identified and, at least for this data set, the matching hypothesis is not confirmed. Possible interpretations of these findings are discussed.

Possible isozyme-specific effects of experimental malaria infection with Plasmodium berghei on cytochrome P450 activity in rat liver microsomes

We have investigated the effect of experimental malaria infection on rat cytochrome P450-mediated drug metabolism using ethoxyresorufin and metoprolol as probe compounds. Malaria infection caused a significant reduction in total intrinsic clearance of ethoxyresorufin in both low and high parasitaemia malaria compared with control (control 18.7 +/- 7.2; low parasitaemia 10.5 +/- 4.1; high parasitaemia 4.3 +/- 1.4 mL min-1). However, clearance of metoprolol was unchanged in malaria infection compared with control (control 2.7 +/- 1.2; malaria 4.0 +/- 1.7 mL min-1). The change in clearance of ethoxyresorufin was the result of a decrease in Vmax, with no apparent change in Km. There was no change in either Vmax or Km of metoprolol. These results indicate a possible isozyme-selective effect of experimental malaria.

Pharmacokinetics of artemether after oral administration to healthy Thai males and patients with acute, uncomplicated falciparum malaria

1. The pharmacokinetics of artemether were investigated (a) in six healthy male Thai volunteers after single 200 mg oral doses and (b) in eight male Thai patients with acute uncomplicated falciparum malaria after an initial 200 mg oral dose followed by 100 mg at 12 h then 100 mg daily for 4 days. 2. In the healthy subjects, median (range) maximum plasma concentrations of artemether of 118 (112-127) ng ml-1 were reached at 3 (1-10) h. Thereafter, drug concentrations declined monoexponentially with a median (range) t1/2.z of 3.1 (1.0-9.6) h. The median (range) AUC and MRT values were 1.10 (0.33-4.44) micrograms ml-1 h and 8.3 (3.5-20.8) h. The median Cmax value of dihydroartemisinin, an active metabolite, was 379 (162-702) mg ml-1 at 6 (2-12) h. Its median AUC value was 6.6 (0.83-38.7) micrograms ml-1 h; the apparent t1/2.z was 10.6 (4.7-19.2) h and the median MRT value was 16.0 (5.0-41.0) h. 3. In the patients, a higher Cmax value of parent drug than those observed in healthy subjects (median and range of 231 (116-411) ng ml-1), was reached at 3 (1-3) h after the first dose. Steady state was reached after the third dose (24 h) and concentrations fluctuated over the range of 36-60 ng ml-1. The respective median (range) values of AUC and t1/2.z were 5.8 (3.76-12.9) micrograms ml-1 h and 4.2 (2.5-5.3) h.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment with coumarin to prevent or delay recurrence of malignant melanoma

Both coumarin (1,2-benzopyrone) and warfarin (4-hydroxycoumarin) have been shown to prevent the recurrence of malignant melanoma. Their action is macrophage-dependent and the dosage is critical. In 1984 a multicentre, prospective, randomised, double-blind trial of coumarin, given as a daily 50-mg dose for 2 years after surgery in patients with high-risk melanoma, was started. the patients had lesions greater than 1.70 mm thick and TNM stage IB or stage II disease. To date there are 4 recurrences in the coumarin-treated group of 13 patients, and 10 recurrences in the placebo-treated group of 14 patients (P < 0.01). There were no toxic effects.

Metabolism of caffeine and theophylline in rats with malaria and endotoxin-induced fever

1. The effects of malaria infection due to Plasmodium berghei and Escherichia coli endotoxin-induced fever on the metabolism of orally-administered caffeine (CA: 10 mg/kg) to its primary metabolites (theobromine (TB), paraxanthine (PX) and theophylline (TH)) were studied in 5-week-old male Wistar rats (n = 5 for each treatment). In separate experiments, the effects of malaria and endotoxin-induced fever on the clearance of i.v.-administered theophylline (TH; 15 mg/kg) were studied in another group of rats. 2. The ratios of CA to the three primary metabolites (TB/CA, PX/CA, PH/CA) determined in a single plasma sample obtained 3 h after CA administration were significantly reduced (p < 0.05) both by malaria and fever compared with control (saline) treatment. The clearance of TH determined from the concentration of TH in a single plasma sample obtained 6 h after TH administration was significantly reduced (p < 0.05) by fever but not malaria (4.0 +/- 0.7 ml/min/kg in controls; 4.2 +/- 0.5 in malaria; 2.4 +/- 0.4 in fever). 3. These results suggest that malaria and fever have different effects on CA and TH metabolism in vivo, probably as a result of different effects on the hepatic isozymes involved.

Antagonism of levcromakalim by imidazoline- and guanidine-derivatives in rat portal vein: involvement of the delayed rectifier

1. In rat whole portal veins, guanabenz (100 nM to 10 microM) and antazoline (100 nM to 100 microM) each increased the amplitude, frequency and duration of spontaneous contractions. In addition, guanabenz (30 microM) and antazoline (30 microM) each antagonized the ability of levcromakalim (3 nM to 10 microM) to inhibit the spontaneous contractions of this tissue. 2. Whole-cell voltage-clamp recordings were made from freshly-isolated rat portal vein cells dispersed by a collagenase/pronase enzyme treatment. The ability of several agents (antazoline, cirazoline, clonidine, guanabenz and phentolamine, each containing an imidazoline or guanidine moiety), to modulate potassium (K) currents and to inhibit the actions of levcromakalim was investigated. 3. Antazoline, cirazoline, clonidine, guanabenz and phentolamine (each at a concentration of 30 microM) had little effect on control non-inactivating currents but inhibited the delayed-rectifier current, IK(V). 4. Levcromakalim (1 microM) induced a non-inactivating current, IK(ATP), and also inhibited the delayed rectifier current, IK(V). 5. Glibenclamide (1 microM) had no effect on control delayed rectifier or non-inactivating currents, but it inhibited the simultaneous induction of IK(ATP) and reduction of IK(V) produced by levcromakalim (1 microM). 6. Antazoline, cirazoline, clonidine and guanabenz (each at a concentration of 30 microM) prevented the induction of IK(ATP) by levcromakalim (1 microM). Phentolamine (30 microM) and clonidine (30 microM) each inhibited the IK(ATP) generated by levcromakalim (1 microM). 7. It is concluded that a variety of agents which possess either an imidazoline (antazoline, cirazoline, clonidine and phentolamine) or a guanidine (guanabenz) moiety within their structure inhibit the delayed rectifier current, IK(V). This action may thus be mediated via a so-called non-adrenoceptor imidazoline binding site. Furthermore, the ability of these ligands to inhibit IK(V) and to antagonize both the induction of IK(ATP) and the vasorelaxation produced by levcromakalim is consistent with the view that the channel (KATP) which underlies IK(ATP) is a voltage-insensitive state of the delayed rectifier K-channel (Kv).

Induction of a glibenclamide-sensitive K-current by modification of a delayed rectifier channel in rat portal vein in insulinoma cells

In insulinoma cells (RINm5F), the glibenclamide-sensitive K-current (IK(ATP)) which developed spontaneously or after exposure to levcromakalim or to butanedione monoxime was always accompanied by a reduction in the delayed rectifier current (IK(V)). At potentials over which IK(V) was fully activated, the total outward current remained constant. In rat portal vein, the delayed rectifier channel inhibitor, margatoxin, reduced the combined induction of IK(ATP) and inhibition of IK(V) by levcromakalim. These data suggest that the ATP-sensitive K-channel, K(ATP), is a voltage-insensitive state of the delayed rectifier, KV.

Levcromakalim may induce a voltage-independent K-current in rat portal veins by modifying the gating properties of the delayed rectifier

1. Smooth muscle cells of the rat portal vein were dispersed by enzymatic treatment and recordings of whole-cell currents under calcium-free conditions were made by the voltage-clamp technique. The effects of the potassium (K)-channel opener, levcromakalim, on K-currents were compared with those of agents which modify protein phosphorylation. 2. Levcromakalim (1-10 microM) added to the extracellular (bath) fluid caused the development of a non-inactivating current (IK(ATP)) and simultaneously inhibited the delayed rectifier current (IK(V)) in a concentration-dependent manner. On prolonged exposure to levcromakalim (10 microM), IK(ATP) declined and IK(V) was further diminished. 3. Addition to the pipette (intracellular) solution of the selective inhibitor of protein kinase C, calphostin C, itself had no effect on K-currents and did not modify the induction of IK(ATP) or the simultaneous inhibition of IK(V) produced by 1 microM levcromakalim. 4. Addition of the protein kinase inhibitor (PKI(6-22)amide, 1 microM) to the pipette solution caused the production of a glibenclamide-sensitive, non-inactivating current and inhibited IK(V). 5. In an assay system, levcromakalim (10 microM) did not inhibit the activity of purified protein kinase A (Type 1 or Type 2). 6. Addition to the pipette solution of the phosphatase inhibitor, okadaic acid (1 microM), did not itself modify K-currents and had little effect on the simultaneous induction of IK(ATP) and inhibition of IK(V) by levcromakalim (1 microM). 7. When the pipette solution contained 1 mM MgATP (but was depleted of substrates for ATP production), a non-inactivating, glibenclamide-sensitive K-current developed spontaneously in 5 out of 11 cells with the simultaneous reduction of IK(V). In 3 of the 6 remaining cells, addition of the dephosphorylating agent, butanedione monoxime (5 mM) to the bath inhibited IK(V) and stimulated a glibenclamide-sensitive non-inactivating current. 8. Depletion of intracellular Mg2+ slightly enhanced IK(V). Under these conditions, levcromakalim (1 microM and 10 microM) did not significantly induce IK(ATP) or inhibit IK(V). 9. It is concluded that the effects of levcromakalim on K-currents can be mimicked by procedures designed to reduce channel phosphorylation. The results are consistent with the view that levcromkalim dephosphorylates the delayed rectifier channel, KV, which becomes converted into a voltage-independent, non-inactivating form known as KATP. The possible mechanisms which underlie this interconversion are discussed.

Flurbiprofen in the prevention and treatment of experimental gingivitis

A clinical trial was undertaken to examine the effects of a potent cyclooxygenase inhibitor, flurbiprofen, on both developing and established gingivitis in humans. 21 subjects with healthy gingiva abstained from all oral hygiene procedures for 21 days. 7 subjects were prescribed flurbiprofen, 50 mg b.d. beginning from baseline and a control group (Cl, n = 14) were given placebo. Gingival redness and bleeding on probing were assessed at baseline, 7, 14 and 21 days. Crevicular fluid (GCF) samples were also taken to determine concentrations of PGE2, TxB2 and LTB4 at baseline and at 21 days. Results show that flurbiprofen significantly inhibited the development of redness and bleeding (p < 0.001) effects which were associated with a significant inhibition of TxB2 (p < 0.05). There were no apparent flurbiprofen effects on GCF-PGE2 or GCF-LTB4 during this 21-day gingivitis, model To assess the effects of flurbiprofen on established experimental gingivitis, the model was extended to 28 days. On day 21, the Cl group was subdivided into 2 groups of 7 subjects. One group was prescribed flurbiprofen (50 mg b.d.) for 7 days and controls (C2) continued to take placebo. All subjects continued to abstain from tooth cleaning. Pretreatment (day 21) and post-treatment (day 28) comparisons showed that flurbiprofen again significantly inhibited bleeding (p < 0.001), but did not affect redness. Control subjects demonstrated a significant elevation in gingival bleeding on day 28, and this was associated with significant rises in GCF-PGE2 (p < 0.001), GCF-TxB2 (p < 0.01) and GCF-LTB4 (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute resistance exercise on postexercise energy expenditure and resting metabolic rate

Two separate experiments were performed to determine the effect of acute resistive exercise on postexercise energy expenditure in male subjects previously trained in resistive exercise. In experiment 1, after measurement of their resting metabolic rate (RMR) at 0700 h and their ingestion of a standardized meal at 0800 h, seven subjects (age range 22-40 yr) beginning at 1400 h completed a 90-min weight-lifting protocol. Postexercise metabolic rate (PEMR) was measured continuously for 2 h after exercise and compared with a preexercise baseline. RMR was measured the following morning 15 h after completion of the workout. In experiment 2, six different men (age range 20-35 yr) completed a similar experimental protocol as well as a control condition on a separate day in which metabolic rate was measured for 2 h after a period of quiet sitting. For both experiments, PEMR remained elevated for the entire 2-h measured recovery period, with the average oxygen consumption for the last 6 min elevated by 11-12%. RMR measured the morning after exercise was 9.4% higher in experiment 1 and 4.7% higher in experiment 2 than on the previous day. In experiment 2, the postabsorptive respiratory exchange ratio was significantly lower the morning after the exercise bout. Strenuous resistive exercise may elevate PEMR for a prolonged period and may enhance postexercise lipid oxidation.

Bupivacaine and Kaltostat reduces post-operative donor site pain

A prospective double blind controlled trial was carried out to examine the differences in post-operative split skin graft donor site pain between sites dressed with three differently treated types of dressing; a dry calcium alginate dressing (Kaltostat Britcair), a saline moistened Kaltostat dressing and a bupivacaine hydrochloride (0.5%) moistened Kaltostat dressing. There was a significant reduction in post-operative pain in the Kaltostat and bupivacaine group (group 3) at 24 and 48 h when compared to the other two groups (p < 0.04). There was no difference in ease of removal of dressings or the quality of wound healing on day 10 between the three groups. This study demonstrates a significant reduction in post-operative pain in bupivacaine soaked Kaltostat without reducing the beneficial effects of Kaltostat on donor site healing and we recommend its use in clinical practice.

The multiple dose pharmacokinetics of proguanil

Proguanil, a prophylactic antimalarial agent, is metabolised by the polymorphic isoenzyme CYP2Cmep in man. In this study the multiple dose pharmacokinetics of proguanil were investigated in subjects who were phenotyped previously as extensive (n = 6) or poor (n = 2) metabolisers of the drug. Steady-state plasma concentrations of proguanil were achieved within 48 h in extensive metaboliser subjects and chronic administration of the drug did not appear to alter the disposition of proguanil or that of its active metabolite, cycloguanil. The currently recommended dosage regimen appears to be appropriate for extensive metabolisers of proguanil. Poor metabolisers of proguanil had significantly lower plasma concentrations of the active metabolite cycloguanil compared with extensive metabolisers. Thus, even on multiple dose administration these subjects may not achieve adequate plasma concentrations of cycloguanil. Deficient metabolism of proguanil to cycloguanil leads to an increased appearance of the N-dealkylated metabolite p-chlorphenylbiguanide in the urine of poor metabolisers.

Doctors and substance misuse: types of doctors, types of problems

The casenotes of 144 doctors who had received treatment for substance misuse were analysed. There were no differences between general practitioners (n = 61) and hospital doctors (n = 58) in terms of their substance misuse histories or the problems they incurred. Differences emerged between the consultant (n = 24) and the non-consultant (n = 34) grades of hospital doctor. The consultants were older at onset of problematic use (42.6 +/- 8.6 vs. 29.9 +/- 9.8 years); they suffered fewer career problems and misused fewer substances. The most frequent pathways into substance use were personality difficulties (76 subjects, 52.8%) and anxiety or depression (46 subjects, 31.9%). A history of depression (n = 36) was associated with perceived stress at work (p = 0.014), and at home (p = 0.06). Past neurotic disturbances (n = 20) were associated with personality difficulties (p = 0.035), anxiety or depression (p = 0.004), and with an earlier onset of problematic substance use (30.2 +/- 8.3 vs. 36.5 +/- 9.8 years, p = 0.014). Principal components of possible antecedents yielded one major component on which all elements loaded; this was labelled the 'disturbance score'. This score showed a reduction with increasing age of onset of problematic substance use.

Transcription factor E2F binds DNA as a heterodimer

E2F is a mammalian transcription factor that appears to play an important role in cell cycle control. DNA affinity column-purified E2F from HeLa cells reproducibly exhibits multiple protein bands when analyzed by SDS/PAGE. After electrophoretic purification, electroelution, and refolding of the individual protein components, the E2F DNA binding activity of the individual proteins was poor. However, upon mixing the individual components together, a dramatic (100- to 1000-fold) increase in specific DNA binding activity was observed. The five protein bands isolated can be separated into two groups based on apparent molecular mass. Optimal reconstitution of activity requires one of the two proteins found in the group of larger molecular mass (approximately 60 kDa) and one of the three proteins in the smaller-sized group (approximately 50 kDa). The reconstituted heterodimer is identical to authentic affinity-purified E2F by three criteria: DNA-binding specificity, DNA pattern, and binding to the retinoblastoma gene product. A recently cloned protein with E2F-like activity, RBP3/E2F-1, is related to the protein components of the group of larger molecular mass, as determined by Western blot analysis and reconstitution experiments. These data suggest that E2F, like many other transcription factors, binds DNA as an oligomeric complex composed of at least two distinct proteins.

Effects of P1060 and aprikalim on whole-cell currents in rat portal vein; inhibition by glibenclamide and phentolamine

1 Smooth muscle cells of the rat portal vein were dispersed by enzymatic treatment and recordings of whole-cell currents were made by the voltage-clamp technique. The effects of the potassium (K) channel openers, P1060 (0.3-10 microM) and aprikalim (3-30 microM) on these currents were investigated. Antagonism of these agents by glibenclamide and phentolamine was also studied. 2 When cells were clamped at -10 mV, P1060 (1 microM) and aprikalim (3 microM) each induced a slowly-developing K-current (IKCO), the noise of which gradually increased. The rate of onset of IKCO was greater for P1060 than for aprikalim. Current-voltage plots showed that P1060 and aprikalim each caused an approximately 25 mV negative shift of the reversal potential at zero current. 3 P1060 (1 microM) and aprikalim (3 microM) each inhibited the slowly activating, slowly inactivating delayed rectifier current, ITO. 4 Addition of MgATP (5 mM) to the recording pipette inhibited the generation of IKCO by P1060 (1 microM) and reduced the accompanying inhibition of ITO. 5 Stationary fluctuation analysis of the current noise associated with IKCO induced by P1060 (1 microM) or aprikalim (3 microM) at a holding potential of -10 mV indicated that the unitary conductance of the underlying K-channels was 10.5 pS at 0 mV under the quasi-physiological conditions of the experiment. 6 In the absence of K-channel openers, neither phentolamine (30-100 microM) nor glibenclamide (1 microM) affected the magnitude of control non-inactivating currents. However, phentolamine (30-100 microM), but not glibenclamide (1 microM) inhibited the control delayed rectifier current ITO. 7. After induction of IKCO by P1060 (1 microM) or aprikalim (3 microM), subsequent exposure to glibenclamide(1 microM) or phentolamine (30 microM) inhibited this current. After aprikalim-induced reduction of ITO had developed, subsequent exposure to glibenclamide was able partially to reverse the inhibition of ITO whereas phentolamine was without effect. Pre-exposure to glibenclamide (1 microM) prevented both the generation of IKCO by aprikalim (3 microM) and the inhibitory effect of this agent on ITO.8. It is concluded that P1060 and aprikalim each induce the current IKCO by opening the same small conductance, ATP-sensitive K-channel (KATP), an effect which can be inhibited by glibenclamide orphentolamine. The opening of KATP by both P1060 and aprikalim probably involves competition between these agents and ATP for the ATP-control site associated with the channel. Inhibition of the delayed rectifier current, ITO, by P1060 and aprikalim was glibenclamide-sensitive and may be caused by the induction of a state of run-down in the channel which underlies this current.

Effect of malaria infection and endotoxin-induced fever on phenacetin O-deethylation by rat liver microsomes

We have investigated the effect of malaria infection with the rodent parasite Plasmodium berghei and fever induced by Escherichia coli endotoxin on the metabolism of phenacetin to paracetamol by rat liver microsomes from young (4 weeks old) male Wistar rats (N = 5 in control and fever groups; N = 10 in malaria-infected group). Following determination of % parasitaemia, the malaria-infected group was divided into a low parasitaemia subgroup (N = 5; mean % parasitaemia = 9.87 +/- 2.6) and a high parasitaemia subgroup (N = 5; mean % parasitaemia = 36.6 +/- 8.1). The control group received normal saline. Total microsomal protein was not significantly affected by fever or malaria infection while cytochrome P450 levels were reduced by approximately 50% in the high parasitaemia subgroup, 20% in the low parasitaemia subgroup and 20% in the endotoxin-treated group. Phenacetin-O-deethylation kinetics were biphasic in both control and malaria-infected rats, but monophasic in endotoxin-treated rats. Total apparent intrinsic clearance (CL(int),total; calculated as Vmax/Km; Vmax is maximum velocity, Km is Michaelis constant) of phenacetin was reduced approximately 6-fold in low parasitaemia, 30-fold in high parasitaemia and 35-fold in fever. There was a poor correlation between CL(int),total and % parasitaemia (r = -0.6). However, log CL(int),total correlated inversely with % parasitaemia (r = -0.9), suggesting that Cl(int),total decreased exponentially with an increase in % parasitaemia. Phenacetin O-deethylation is a marker for cytochrome P4501A2 activity and the results of the present study suggest that both malaria infection and fever might specifically reduce P4501A2 activity in the rat.