Ketoprofen Absorption by Muscle and Tendon after Topical or Oral Administration in Patients Undergoing Anterior Cruciate Ligament Reconstruction

Topical ketoprofen patches are widely used in the treatment of musculoskeletal pain, but the pharmacokinetics of ketoprofen following topical application remain unclear. This open-label, single-dose pharmacokinetic study was designed to determine the concentrations of ketoprofen in the semitendinosus muscle/tendon and plasma after topical application or oral administration to patients scheduled for anterior cruciate ligament reconstruction. Two ketoprofen patches (20 mg each) were applied over the semitendinosus muscle/tendon for 1, 6, 14, or 20 h before surgery in 21 patients, while one sustained-release 150 mg ketoprofen capsule was administered to six patients 14 h before surgery. Ten untreated patients served as the control group. The main outcome measures were the semitendinosus muscle/tendon and plasma concentrations of ketoprofen at 1, 6, 14, and 20 h. Ketoprofen was detected in the semitendinosus muscle/tendon from about 1 h after topical application. The peak concentration was reached at 6 h, and it decreased gradually until 20 h, although the concentration at 20 h was still higher than that at 1 h. Unlike the tissue concentration, the plasma concentration of ketoprofen increased gradually after topical application. At 14 h, there was no significant difference of the tissue concentration between the topical and oral groups, although the plasma concentration was about 17-fold higher in the oral group than in the topical group. In conclusion, following topical application in a patch, ketoprofen shows rapid and sustained delivery to the underlying tissues without a significant increase of the plasma drug concentration.     

Prostaglandin biosynthesis inhibitors and endometriosis

The prostaglandin biosynthesis inhibitors ketoprofen and indomethacin were compared in the treatment of primary dysmenorrhea in a double-blind, cross-over trial involving 23 patients. Each drug was used for 2–4 days during 3 consecutive menstruations in randomized order. Good or moderate overall relief was obtained in 60 of the 68 ketoprofen-treated menstruations (88 %) and in 60 of the indomethacin-treated cases (90 %). A dysmenorrhea score, based on subjective estimations of 8 symptoms, similarly decreased from a mean (±S.E.M.) basal level of 9.6 ± 0.6 to 3.6 ± 0.3 during ketoprofen treatment and to 4.0 ± 0.3 during indomethacin. Both drugs relieved pelvic and lower back pains and eliminated vomiting and diarrhea in 82–97 % of the cycles whereas headache, fatigue and nervousness were less frequently alleviated (40–67 %). Eighteen of the 23 women (78 %) had been unable to work during the first day of menstruation, the rate of working days lost was reduced to 4 % with ketoprofen and 9 with indomethacin. Mild side-effects occurred during 12 ketoprofen and 14 indomethacin therapies. Ketoprofen thus seems to be as effective and tolerable as indomethacin in the treatment of primary dysmenorrhea.     

Quantitation of mitomycin C in human ocular tissues by high-performance liquid chromatography–photo-diode array detection

A chromatographic method, which can quantitate mitomycin C (MMC) along with two antiglaucoma drugs, is described. The separation of MMC, alphagan and timolol was performed on a reversed-phase C₁₈ column with water–methanol–trifluoroacetic acid (65:35:0.01, v/v) as the mobile phase. By monitoring at 360, 248 and 296 nm, the lower limits of detection for MMC, alphagan and timolol are, respectively, 1.0, 2.0 and 5.0 ng (injection amount) at three-time S/N ratio. The dynamic ranges of quantitation for the three drugs are, respectively, 1.0 ng–10.0 μg, 2.0 ng–10.0 μg and 5.0 ng–10.0 μg with linearity being larger than 0.9960. This method was applied to the determination of MMC levels in Tenon’s and trabeculum tissues of 10 glaucoma patients. MMC levels in these tissues, which were obtained from glaucoma filtering surgery, were determined following a multiple extraction with methanol. The recovery of MMC for a two-batch extraction was better than 91.2%. The reproducibility of measurement for the MMC levels in these tissues is 2.5–6.0% RSD for triplicate injections. The intra-day variation of retention times for the MMC peaks was less than 1.6% RSD (n=3). The inter-day variation of retention times for the MMC peaks was less than 4.8% RSD (n=3). MMC was detectable in three trabeculum tissues out of 10 cases (ranging from 0.8 to 25.5 ng/mg specimen), while MMC was detected in nine Tenon’s tissues out of 10 cases (ranging from 0.3 to 21.1 ng/mg specimen). The results obtained show that the method is sensitive and selective for the quantitation of MMC.     

Isolation, identification and determination of sulfamethoxazole and its known metabolites in human plasma and urine by high-performance liquid chromatography

From human urine the following metabolites of sulfamethoxazole (S) were isolated by preparative HPLC: 5-methylhydroxysulfamethoxazole (SOH), N₄-acetyl-5-methylhydroxysulfamethoxazole (N₄SOH) and sulfamethoxazole-N₁-glucuronide (Sgluc). The compounds were identified by NMR, mass spectrometry, infrared spectrometry, hydrolysis by β-glucuronidase and ratio of capacity factors. The analysis of S and the metabolites N₄-acetylsulfamethoxazole (N₄), SOH, N₄-hydroxysulfamethoxazole (N₄OH), N₄SOH, and Sgluc in human plasma and urine samples was performed with reversed-phase gradient HPLC with UV detection. In plasma, S and N₄ could be detected in high concentrations, while the other metabolites were present in only minute concentrations. In urine, S and the metabolites and conjugates were present. The quantitation limit of the compounds in plasma are respectively: S and N₄ 0.10 μg/ml; N₄SOH 0.13 μg/ml; N₄OH 0.18 μg/ml; SOH 0.20 μg/ml; and Sgluc 0.39 μg/ml. In urine the quantitation limits are: N₄ and N₄OH 1.4 μg/ml; S 1.5 μg/ml; N₄SOH 1.9 μg/ml; SOH 3.5 μg/ml; and Sgluc 4.1 μg/ml. The method was applied to studies with healthy subjects and HIV positive patients.     

Determination of indomethacin and mefenamic acid in plasma by high-performance liquid chromatography

Indomethacin and mefenamic acid are widely used clinically as non-steroidal anti-inflammatory agents. Both drugs have also been found effective to produce closure of patent ductus arteriosus in premature neonates. A simple, rapid, sensitive and reliable HPLC method is described for the determination of indomethacin and mefenamic acid in human plasma. As these drugs are not applied together, the compounds are alternately used as analyte and internal standard. Plasma was deproteinized with acetonitrile, the supernatant fraction was evaporated to dryness and the resulting residue was reconstituted in the mobile phase and injected into the HPLC system. The chromatographic separation was performed on a C₁₈ column (250 × 4.6 mm I.D.) using 10 mM phosphoric acid—acetonitrile (40:60, v/v) as the mobile phase and both drugs were detected at 280 nm. The calibration graphs were linear with a correlation coefficient (r) of 0.999 or better from 0.1 to 10 μg/ml and the detection limits were 0.06 μg/ml for indomethacin and 0.08 μg/ml for mefenamic acid, for 50μl plasma samples. The method was not interfered with by other plasma components and has been found particularly useful for paediatric use. The within-day precision and accuracy of the method were evaluated for three concentrations in spiked plasma samples. The coefficients of variation were less than 5% and the accuracy was nearly 100% for both drugs.     

Simultaneous analysis of several non-steroidal anti-inflammatory drugs in human urine by high-performance liquid chromatography with normal solid-phase extraction

A practical and reproducible high-performance liquid chromatographic method using normal solid-phase extraction has been developed for the simultaneous analysis of twelve non-steroidal anti-inflammatory drugs (NSAIDs) in human urine. A urine specimen mixed with acetate buffer pH 5.0 was purified by solid-phase extraction on a Sep-Pak Silica cartridge. The analyte was chromatographed by a reversed-phase Inertsil ODS-2 column using a phosphate buffer-acetonitrile at pH 5.0 as the mobile phase, and the effluent from the column was monitored at 230 or 320 nm. Absolute recoveries were greater than 73% for all of the twelve NSAIDs. The present method enabled simple manipulation and isocratic HPLC with UV analysis as well as high sensivity of 0.005 μg/ml for naproxen, and 0.05 μg/ml for sulindac, piroxicam, loxoprofen, ketoprofen, felbinac, fenbufen, flurbiprofen, diclofenac, ibuprofen and mefanamic acid as the quantitation limit in human urine using indomethacin as an internal standard.     

Toxicity of non-steroidal anti-inflammatory drugs to Gyps vultures: a new threat from ketoprofen

Three Gyps vulture species are on the brink of extinction in South Asia owing to the veterinary non-steroidal anti-inflammatory drug (NSAID) diclofenac. Carcasses of domesticated ungulates are the main food source for Asia''s vultures and birds die from kidney failure after consuming diclofenac-contaminated tissues. Here, we report on the safety testing of the NSAID ketoprofen, which was not reported to cause mortality in clinical treatment of scavenging birds and is rapidly eliminated from livestock tissues. Safety testing was undertaken using captive non-releasable Cape griffon vultures (Gyps coprotheres) and wild-caught African white-backed vultures (G. africanus), both previously identified as susceptible to diclofenac and suitable surrogates. Ketoprofen doses ranged from 0.5 to 5 mg kg⁻¹ vulture body weight, based upon recommended veterinary guidelines and maximum levels of exposure for wild vultures (estimated as 1.54 mg kg⁻¹). Doses were administered by oral gavage or through feeding tissues from cattle dosed with ketoprofen at 6 mg kg⁻¹ cattle body weight, before slaughter. Mortalities occurred at dose levels of 1.5 and 5 mg kg⁻¹ vulture body weight (within the range recommended for clinical treatment) with the same clinical signs as observed for diclofenac. Surveys of livestock carcasses in India indicate that toxic levels of residual ketoprofen are already present in vulture food supplies. Consequently, we strongly recommend that ketoprofen is not used for veterinary treatment of livestock in Asia and in other regions of the world where vultures access livestock carcasses. The only alternative to diclofenac that should be promoted as safe for vultures is the NSAID meloxicam.     

Determination of acetylsalicylic acid and salicylic acid in skin and plasma by high-performance liquid chromatography

This study describes a HPLC method to determine the concentrations of acetylsalicylic acid (ASA) and salicylic acid (SA) in human stratum corneum and in plasma. The stratum corneum layers for ASA/SA analysis were removed from three patients with postherpetic hyperalgesia treated with topical and oral aspirin. Blood samples were also collected from the same patients. Tape strippings were placed in acetonitrile and sonicated for 15 min. After centrifuging, aliquots of the supernatant were injected into the chromatograph. ASA and SA from plasma samples were extracted on Isolute C₈ columns. Due to interfering peaks in the tape samples, HPLC conditions were slightly different for tape and plasma samples. ASA and SA were separated on a LiChrospher 100 RP-18 column at 1 ml/min using a water–phosphate buffer (pH 2.5)–acetonitrile mobile phase (35:40:25, v/v/v). A linear response to quantities of ASA from 0.1 to 100 μg/cm² and of SA from 0.1 to 5 μg/cm² in tape and to quantities of ASA 0.1 to 2 μg/ml and 1 to 50 μg/ml was obtained and the recovery from tape and plasma samples was over 98%. The method is sensitive (0.1 μg/cm²) and specific enough to allow the determination of the drugs in the skin not only after topical but also after oral administration. A good sensitivity was also obtained in plasma (0.1 μg/ml) allowing study of the kinetics of ASA and SA in plasma after oral administration. Concentrations of ASA after topical administration were 100–200 times higher than after oral administration. Plasma levels of ASA and SA after oral administration were similar to those previously found. No ASA or SA were detected in plasma after topical ASA administration.     

Biodegradation of ketoprofen using a microalgal–bacterial consortium

Objective

To test the toxicity of ketoprofen (a commonly-used NSAIDs) using two microalgal strains and Artemia sp. following the isolation of bacterial and microalgal strains and testing their ability to biodegrade and tolerate ketoprofen.

Results

Chlorella sp. was the most resistant to ketoprofen. A defined bacterial consortium (K₂) degraded 5 mM ketoprofen as a sole carbon source both in the dark or continuous illumination. Ketoprofen did not undergo photodegradation. In the dark, biodegradation was faster with a lag phase of 10 h, 41% COD removal and 82 % reduction in toxicity. The consortium degraded up to 16 mM ketoprofen. The consortium was composed of four bacterial isolates that were identified. MS/MS analysis suggested a ketoprofen biodegradation pathway that has not been previously reported. Combining Chlorella sp. and the K₂ consortium, ketoprofen was degraded within 7 days under a diurnal cycle of 12 h light/12 h dark.

Conclusion

The feasibility of using a microalgal–bacterial system to treat pharmaceutical wastewater is promising for the reduction of the process cost and providing a safer technology for pharmaceutical wastewater treatment.

     

Determination of aspirin and salicylic acid in transdermal perfusates

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of aspirin and salicylic acid in transdermal perfusates. The compounds were separated on a C₈ Nucleosil column (5 μm, 250×4.6 mm) using a mobile phase containing a mixture of water–acetonitrile–orthophosphoric acid (650:350:2, v/v/v) and a flow-rate of 1 ml/min. The transdermal samples were in phosphate-buffered saline (PBS) and could be injected directly onto the HPLC system. The method was reproducible with inter-day R.S.D. values of no greater than 3.46 and 2.60% for aspirin and salicylic acid, respectively. The method was linear over the concentration range 0.2–5.0 μg/ml and had a limit of detection of 0.05 μg/ml for both compounds. For certain samples, it was necessary to ensure that no transmembrane leakage of the aspirin prodrugs had occurred. In these cases, a gradient was introduced by increasing the acetonitrile content of the mobile phase after the salicylic acid had eluted. The method has been applied to the determination of aspirin and salicylic acid in PBS following in vitro application of the compounds to mouse skin samples.     

High-performance liquid chromatographic determination of oxolinic acid and flumequine in the live fish feed Artemia

A high-performance liquid chromatography (HPLC) analytical method for the determination of oxolinic acid and flumequine in Artemia nauplii is described. The samples were extracted and cleaned up by a solid-phase extraction (SPE) procedure using SPE C₁₈ cartridges. Oxolinic acid and flumequine were determined by reversed-phase HPLC using a mobile phase of methanol–0.1 M phosphate buffer, pH 3 (45:55, v/v) and a UV detection wavelength of 254 nm. Calibration curves were linear for oxolinic acid in the range of 0.2–50 μg/g (r²=0.9998) and for flumequine in the range of 0.3–50 μg/g (r²=0.9994). Mean recoveries amounted to 100.8% and 98.4% for oxolinic acid and flumequine, respectively. The quantification limit was 0.2 μg/g for oxolinic acid and 0.3 μg/g for flumequine. Quantitative data from an in vivo feeding study indicated excellent uptake of both drugs by Artemia nauplii.     

Quantification of ketoprofen enantiomers in human plasma based on solid-phase extraction and enantioselective column chromatography

An HPLC method for the quantification of ketoprofen enantiomers in human plasma is described. Following extraction with a disposable C₁₈ solid-phase extraction column, separation of ketoprofen enantiomers and I.S. (3,4-dimethoxy benzoic acid) was achieved using a chiral column [Chirex 3005; (R)-1-naphthylglycine 3,5-dinitrobenzoic acid] with the mobile phase, 0.02 M ammonium acetate in methanol, set at a flow-rate of 1.2 ml/min. Baseline separation of ketoprofen enantiomers and I.S., free from interferences, was achieved in less than 20 min. The calibration curves (n = 14) were linear over the concentration range of 0.16 to 5.00 μg/ml per enantiomer [mean r² of 0.999 for both enantiomers, root mean square error were 0.015 for R(−) and 0.013 for S(+)]. The inter-day coefficient of variation for duplicate analysis of spiked samples was less than 7% and the accuracy was more than 93% over the concentration range of 0.2 to 4.0 μg/ml for individual enantiomer using 1 ml of plasma sample. This method has been applied to a pharmacokinetic study from healthy human volunteers following the administration of a ketoprofen extended release product (200 mg). This method is simple, fast and should find wide application in monitoring pharmacokinetic studies of ketoprofen.     

Determination of flumequine and 7-hydroxyflumequine in plasma of sheep by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of flumequine and its metabolite 7-hydroxyflumequine in sheep plasma was described. The two compounds were extracted from 100 μl of plasma by liquid–liquid extraction. Aliquots (100 μl) were injected onto the HPLC system and separated on a LiChrospher Select B column with an isocratic system. The compounds were detected by fluorimetric detection for concentrations below 500 μg/l and by UV detection for the concentrations exceeding 500 μg/l. The range of the validated concentrations were 50 000 to 5 μg/l and 500 to 10 μg/l with mean recovery rates of 87±3% and 60±1% for flumequine and 7-hydroxyflumequine, respectively.     

High-performance liquid chromatographic determination of tianeptine in plasma applied to pharmacokinetic studies

An improved analytical method for the quantitative measurement of tianeptine and its main metabolite MC₅ in human plasma was designed. Extraction involved ion-paired liquid–liquid extraction of the compounds from 1.0 ml of human plasma adjusted to pH 7.0. HPLC separation was performed using a Nucleosil C₁₈, 5 μm column (150×4.6 mm I.D.) and a mixture of acetonitrile and pH 3, 2.7 g l⁻¹ solution of sodium heptanesulfonate in distilled water (40:60, v/v) as mobile phase. UV detection was performed using a diode array detector in the 200–400 nm passband, and quantification of the analytes was made at 220 nm. For both tianeptine and MC₅ metabolite, the limit of quantitation was 5 μg l⁻¹ and the calibration curves were linear from 5 to 500 μg l⁻¹. Intra- and inter-assay precision and accuracy fulfilled the international requirements. The recovery of tianeptine and its metabolite from plasma was, respectively, 71.5 and 74.3% at 20 μg l⁻¹, 71.2 and 70.8% at 400 μg l⁻¹. The selectivity of the method was checked by verifying the absence of chromatographic interference from pure solutions of the most commonly associated therapeutic drugs. This method, validated according to the criteria established by the Journal of Chromatography B, was applied to the determination of tianeptine and MC₅-metabolite in human plasma in pharmacokinetic studies.     

Encapsulation of Ketoprofen and Ketoprofen Lysinate by Prilling for Controlled Drug Release

In this paper, ketoprofen and ketoprofen lysinate were used as model drugs in order to investigate release profiles of poorly soluble and very soluble drug from sodium alginate beads manufactured by prilling. The effect of polymer concentration, viscosity, and drug/polymer ratio on bead micromeritics and drug release rate was studied. Ketoprofen and ketoprofen lysinate loaded alginate beads were obtained in a very narrow dimensional range when the Cross model was used to set prilling operative conditions. Size distribution of alginate beads in the hydrated state was strongly dependent on viscosity of drug/polymer solutions and frequency of the vibration. The release kinetics of the drugs showed that drug release rate was related with alginate concentration and solubility of the drug. Alginate solutions with concentration higher than 0.50% (w/w) were suitable to prepare ketoprofen gastro-resistant formulation, while for ketoprofen lysinate alginate, concentration should be increased to 1.50% (w/w) in order to retain the drug in gastric environment. Differential scanning calorimetry thermograms and Fourier transform infrared analyses of drug-loaded alginate beads indicated complex chemical interactions between carboxyl groups of the drug and polymer matrix in drug-loaded beads that contribute to the differences in release profile between ketoprofen and ketoprofen lysinate. Total release of the drugs in intestinal medium was dependent on the solubility of the drug and was achieved between 4 and 6 h.     

Determination of 9α,11β-prostaglandin F2 by stereospecific antibody in various rat tissues

In view of the recent finding that prostaglandin D₂ is stereospecifically converted to 9α,11β-prostaglandin F₂, an isomer of prostaglandin F₂α, a highly specific and sensitive radioimmunoassay for 9α,11β-prostaglandin F₂ was developed and applied to determine the content of this prostaglandin in various rat tissues. Antisera against 9α-11β-prostaglandin F₂ were raised in rabbits immunized with the bovine serum albumin conjugate, and [³H]9α,11β-prostaglandin F₂ was enzymatically prepared from [³H]prostaglandin D₂. The assay detected 9α,11β-prostaglandin F₂ over the range of 20 pg to 1 ng, and the antiserum showed less than 0.04% cross-section with prostaglandin F₂α, prostaglandin F₂β and 9β,11β-prostaglandin F₂. To avoid postmortem changes, tissues were frozen in liquid nitrogen immediately after removal. The basal level of 9α,11β-prostaglandin F₂ was hardly detectable in various tissues of the rat examined, including spleen, lung, liver and brain; although it was found to be 0.31 ± 0.06 ng/g wet weight in the small intestine. During convulsion induced by pentylenetetrazole, enormous amounts of prostaglandin D₂ (ca. 180 ng/g wet weight) and prostaglandin F₂α (ca. 70 ng/g) were produced in the brain; however, 9α,11β-prostaglandin F₂ was detected neither there nor in the blood. This result demonstrates that the conversion to 9α,11β-prostaglandin F₂ is a minor pathway, if one at all, of prostaglandin D₂ metabolism in the rat brain.     

Determination of lamotrigine in human serum by liquid chromatography

A rapid high-performance liquid chromatographic method was developed using a short silica column (30 mm×4.6 mm) with an aqueous methanol mobile phase consisting of methanol–water–NH₄H₂PO₄ (94:5.96:0.04) adjusted to a final apparent pH of 5.0 and pumped at a flow-rate of 1 ml/min. Ultraviolet detection was carried out at a wavelength of 280 nm, and serum samples were prepared for HPLC analysis by extraction into dichloromethane after basification. Lamotrigine was eluted at 0.96 min. Within-day variation of the method was 4.46% at 0.75 μg/ml and 2.37% at 6.0 μg/ml, and day-to-day variation was 9.10% at 0.75 μg/ml and 7.28% at 6.0 μg/ml.     

Follicle stimulating hormone and prolactin release induced by prostaglandins in rat

Ten to 60 minutes following a single i.v. injection of PGE₂ (500 μg/rat) into male rats of 30 to 35 days of age FSH concentration in the serum was raised significantly. The rise in FSH was maintained from 10 to 60 minutes after treatment, then at 90 minutes FSH had declined and was not significantly different from that of the control before treatment. Prostaglandin E₁, E₂ or F_2α (670μg/rat) significantly increased the serum prolactin level 10 to 60 minutes after a single i.v. injection in spayed rats primed with estrogen and progesterone. And, rats primed with estrogen and progesterone. And, increases in prolactin in the serum were observed with as little as 2μg of PGE₁ or E₂, and 20μg of PGF_2α. Twenty μg of PGE₂, and 200μg of PGE₁ or F_2α gave the maximum stimulation. These results indicate that release of pituitary hormones is affected by prostaglandins.Prostaglandins (PGs) are widely distributed in mammalian tissues, and they have been reported to have an almost equally wide variety of endocrine and metabolic effects. It was recently postulated that PGs may be involved in the process of ovulation because ovulation was blocked by inhibitors of PG synthesis (1–5).     

Determination of the antifungal agent, ketoconazole, in human plasma by high-performance liquid chromatography

A rapid and selective high-performance liquid chromatographic (HPLC) assay for the quantitative determination of ketoconazole, an orally active antifungal agent, in human plasma is described. After extraction of the drug from plasma, the compound is separated by HPLC using a reversed-phase column and detected by UV light at 205 nm. Quantitation is accomplished by external standardization and the determination of peak areas is performed with the aid of an integrating computer. The average recovery of ketoconazole over a concentration range of 0.1–20.0 μg/ml was 88.2 ± 4.07% S.D. The maximum sensitivity of the assay is less than 0.1 μg/ml. The assay is suitable for use in pharmacokinetic studies following the administration of therapeutic doses of ketoconazole to humans.     

Simultaneous determination of seven penicillins in muscle, liver and kidney tissues from cattle and pigs by a multiresidue high-performance liquid chromatographic method

A high-performance liquid chromatographic (HPLC) method based on solid-phase extraction (SPE) was developed for determination of amoxicillin, penicillin G (benzylpenicillin), ampicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin in muscle, liver and kidney tissues of pigs and cattle. The compounds were extracted in aqueous solution by precipitation of organic materials with a mixture of sulphuric acid and sodium tungstate. The extract was cleaned up by SPE on a divinylbenzene-co-N-vinylpyrrolidone polymeric sorbent. Further clean-up was performed by liquid–liquid partition with diethyl ether. The extract was derivatised with benzoic anhydride and 1,2,4-triazole mercury (II) reagent. Chromatography was performed by reversed-phase gradient HPLC on a C₁₈ column with ultraviolet detection at 323 nm. The limits of detection estimated by a conservative model were in the range 8.9–11.1 μg/kg for amoxicillin, penicillin G, ampicillin, oxacillin, cloxacillin and nafcillin and 18.3–20.9 μg/kg for dicloxacillin. The mean recovery range was 66–77% for amoxicillin, 73–75% for penicillin G, 81–82% for ampicillin, 73–76% for oxacillin, 74–75% for cloxacillin, 66–72% for nafcillin and 58–65% for dicloxacillin.