Phenobarbital with chloramphenicol

CHLORAMPHENICOL BARBITURATES 1 levels of these drugs, with risk of therapeutic failure Induction of hepatic metabolism 1. Avoid co-administration of telithromycin for up to 2 weeks after stopping phenobarbital 2. With the other drugs, monitor for 1 clinical efficacy, and t their dose as required... 

There are a large number of publications and papers in which the increase in absolute solubility of active substances by povidone has been tested and described. However, if the selection is restricted to the low-molecular types, this number becomes significantly smaller (Table 93). Naturally, a solubilization effect can also be expected of povidone K 12 and povidone K17, even if such an effect is reported in the literature only for the medium-molecular povidone (see Table 97), though the amounts of active substance complexed may differ according to the molecular weight of povidone (see Table 92). However, the influence of the molecular weight depends very much on the active substance with trimethoprim and chloramphenicol it is very large, while with phenobarbital it is small. 

Another study eonfirmed that this interaction occurred in 20 neonates, but no statistically significant effect was found in 40 infants. Decreased chloramphenicol levels have been described in a single case report of a child who was also being treated with phenytoin and phenobarbital. The serum chloramphenicol levels were 35.1 micrograms/mL prior to the antiepileptics, 19.1 micrograms/mL after 2 days of phenytoin and 13.2 micrograms/mL a month after the addition of phenobarbital. For more information on the interaetion of ehloramphenieol with phenytoin see Phenytoin + Chloramphenieol , p.555. 

A man admitted to hospital on numerous oeeasions for pulmonary eompli-cations associated with cystic fibrosis, had average serum phenobarbital levels of 33 micrograms/mL while taking phenobarbital 200 mg daily and oral chloramphenicol 600 mg every 6 hours. One week after the antibacterial was withdrawn, his serum phenobarbital levels were 24 micrograms/mL even though the phenobarbital dosage was increased from 200 to 300 mg daily. ... 

This interaction appears to be established. The documentation is limited but what happened is consistent with the recognised enzyme-inducing actions of phenobarbital and the inhibitory actions of chloramphenicol. Concurrent use should be well monitored to ensure that chloramphenicol serum levels are adequate, and that phenobarbital levels do not become too high. Make appropriate dosage adjustments as necessary. 

Koup JR, Gibaldi M, McNamara P, HilUgoss DM, Colburn WA, Bruck E. Interaction of chloramphenicol with phen3(toin and phenobarbital. Case report. Clin Pharmacol Ther (1978) 24, 571-5. 

Other drags that suppress hver CYP2C11 and CYP3A2 levels include cyclosporine [203, 204] and chloramphenicol [205], although the latter effects are strain dependent and are associated with a modest reduction in plasma levels of thyroxine but not testosterone [205]. GH does not appear to play a role in the suppression of CYP2C11 and CYP3A2 by cyclosporine, which does not alter the plasma GH peak amplitude, niunber, or duration [206]. Phenobarbital [24, 207, 208], dexa-methasone [28], 5-fluoroiuacil [209], doxorubicin [210], fenofibrate [211], rosuvastatin [212],... 

When 3-methylcholanthrene was injected into normal rats, the urinary excretion of ascorbic acid (an indicator of ascorbic acid synthesis) increased to a large amount with a concomitant increase in hepatic 4-nitrophenol UDPGT activity. However, this phenomenon was not observed in the Gunn rat. On the other hand, injection of phenobarbital into this rat caused a marked increase in urinary excretion of ascorbic acid accompanied by an increase in hepatic activity of another isozyme, chloramphenicol UDPGT. In this situation, this isozyme would have supported the synthesis of ascorbic acid. 

Treatment of mice or rats with phenobarbital significantly increases the rate of disappearance of exogenous bilirubin from the plasma which is accompanied by an increase in bile volume but no alteration in the concentration of bilirubin in the bile suggesting that the accelerated clearance results primarily from enhanced bile flow. However, there does not appear to be a direct relationship between increased biliary flow and microsomal enzyme induction because other enzyme inducers such as chlordane, nikethamide, phenylbutazone, 3-methylcholanthrene. 3,4-benzpyrene, or chlorcyclizine have no effect on bile flow. Other compounds whose rate of clearance from the plasma is accelerated by phenobarbital treatment are bromosulphophthalein (BSP), chlorothiazide, indocyanine green, probenecid, and chloramphenicol Enhanced clearance of the two latter compounds is associated with significant increases in the excretion of glucuronide conjugates. 

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