Tipping the balance.
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Biomedical subjects
Publications and source records attributed to L McTaggart.
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We have demonstrated, with an in vitro model, that Staphylococcus epidermidis is able to colonise intraocular lenses. Adherent organisms were quantitated by light microscopy, scanning electron microscopy, and viable counting. Bacterial adherence was associated with production of a polysaccharide glycocalyx. Organisms which were attached to the lenses were resistant to apparently bactericidal concentrations of antibiotics, as determined by conventional testing. We speculate on the role of colonisation in the pathogenesis of endophthalmitis.
We have studied the pharmacokinetics of single agent high dose cyclophosphamide (HDC) (160-240 mg kg-1) given as repeated intravenous (i.v.) infusions to six patients with small cell lung cancer (SCLC), and HDC (180 mg kg-1) combined with etoposide (750-1000 mg m-2) as repeated i.v. infusions to five patients with SCLC and two patients with teratoma. HDC has a similar pharmacokinetic profile to low dose cyclophosphamide, with a half-life of 4.83 +/- 1.3 h. Repeated administration of HDC produced a small but significant shortening of the half life (P = 0.02). The terminal half-life of high dose etoposide was 7.7 +/- 2 h which is similar to our previous results with low dose etoposide (50-300 mg m-2), but the volume of distribution which was 35.5 +/- 11.6 1. was significantly increased (P less than 0.001). Plasma steady state concentrations of 26.2 +/- 11.7 micrograms ml-1 were achieved. The possible mechanism for the alteration of volume of distribution of etoposide will be discussed.
The pharmacokinetics of intravenous etoposide (50-150 mg m-2) have been studied in 17 patients. Bioavailability studies on either the capsule or intravenous (i.v.) formulation were performed in 13 patients, 7 of whom received both oral formulations given in the dose range 50-250 mg m-2. After i.v. administration the mean +/- SD half-lives were t1/2 alpha 0.62 +/- 1.01 h and t1/2 beta 6.04 +/- 2.5 h. The bioavailability of etoposide was extremely variable: for the capsule it was 38 +/- 14% (range 10-55) and for the i.v. formulation it was 53 +/- 25% (range 31-88). The i.v. formulation was not significantly better than the capsule. The results confirm the low and variable bioavailability of oral etoposide.