Flucloxacillin absorption

Flucloxacillin is a penicillin that must be taken either an hour before food or on an empty stomach for better absorption. 

Both penicillin V and flucloxacillin should be taken on an empty stomach since they are not absorbed well into the bloodstream. Taking these medicines on an empty stomach helps to improve the absorption profile. 

The pharmacology of penicillins differs markedly from compound to compound but has been well reviewed (57). The majority of derivatives, including penicillin G and the antipseudomonal penicillins, are unstable in gastric acid and are not available orally. The isoxazolyl penicillins are relatively acid stable but not consistently well absorbed by the oral route. Nafcillin and oxacillin are poorly absorbed orally cloxacillin, didoxacfllin, and flucloxacillin are more reliable. Penicillin V, ampicillin, and particularly amoxicillin are relatively well absorbed orally. Esters of ampicillin such as bacampicillin, pivampicillin, and talampicillin improve the level of oral absorption of ampicillin to that achieved by amoxicillin. Absorption can be diminished by food after oral administration, however, and peak blood levels, usually achieved after 1 to 2 h, are somewhat delayed after ingestion of food. 

Fludoxadllin. A study in children given flucloxacillin 12.5 mg/kg as either tablets or mixture found that while the absorption depended on both the formulation and age of the child, there was no difference in levels achieved when given to a subject when fasting or with a breakfast.However, it is recommended that flucloxacillin is taken one hour before food or on an empty stomach to optimise absorption. The presence of food is reported to reduce the rate and extent of absorption of the related drug cloxacillin," and therefore it may be prudent to follow the advice given for flucloxacillin. 

Bergdahl S, Eriksson M, Finkel Y, Lannergren K. Oral absorption of flucloxacillin in infants and young children. Acta Pharmacol Toxicol (Copenh) (198 58, 255-8. 

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