Dicloxacillin

Absorption

Absorption of the isoxazolyl penicillins after oral administration is rapid but incomplete: peak blood levels are achieved in 1-1.5 hours. Oral absorption of cloxacillin, dicloxacillin, oxacillin and nafcillin is delayed when the drugs are administered after meals.

Toxicity

Oral LD50 in rat is 3579 mg/kg. Symptoms of overexposure include irritation, rash, labored breathing, hives, itching, wheezing, nausea, chills, and fever.

Description

Chemically this is 3(2,6-dichlorophenyl)-5-methyl-4-isoxazolyl penicillin. It differs from cloxacillin by having two chloride ions attached to the phenyl group. It comes as oral capsules of 250 and 500 mg, and in an injectable formulation of 500 mg and 1 g.

Originator

Dynapen,Bristol,US,1968

The Uses of Dicloxacillin

Antibacterial.

Indications

Used to treat infections caused by penicillinase-producing staphylococci which have demonstrated susceptibility to the drug.

Background

One of the penicillins which is resistant to penicillinase.

Definition

ChEBI: A penicillin that is 6-aminopenicillanic acid in which one of the amino hydrogens is replaced by a 3-(2,6-dichlorophenyl)-5-methyl-1,2-oxazol-4-yl]formyl group.

Manufacturing Process

A suspension of 6-aminopenicillanic acid (216 grams) in water (2 liters) was adjusted to pH 6.8 by the addition of N aqueous sodium hydroxide (approximately 1 liter) and the resulting solution was stirred vigorously while a solution of 3-(2',6'-dichlorophenyl)-5-methylisoxazole-4-carbonyl chloride (290 grams) in acetone (1.5 liters) was added in one portion.
The temperature rose to 26°C and as reaction proceeded the free acid form of the penicillin separated as a white solid. After 30 minutes the suspension was cooled to 10°C and stirring was continued at this temperature for 1 hour more. The mixture was then cooled to 0°C, centrifuged, and the solid product washed with aqueous acetone (250 ml) and finally dried in an air oven at 30°C. The product (440 grams, 94%) had [α]D20 +106.3° (c 1 in EtOH) and was shown by alkalimetric assay to be 97.5% pure.
The salt was prepared by dissolving the free acid form of the penicillin in the equivalent amount of aqueous sodium bicarbonate and freeze drying the resulting solution. The hydrated salt so obtained was shown by alkalimetric assay to be 94% pure and to contain 6% water.

Therapeutic Function

Antibacterial

Antimicrobial activity

It is very highly bound to serum protein, and its activity in the presence of human serum in vitro is depressed to a greater extent than that of other isoxazolylpenicillins.

General Description

Dicloxacillin was synthesized by Bayer in 1965 starting with 6-aminopenicillanic acid. It is a penicillinase-stable and orally active semisynthetic penicillin and shows higher and longer serum concentrations than cloxacillin when administered orally. Dicloxacillin is used orally, either alone or in combination with ampicillin, to treat various infections, including those caused by benzylpenicillin-resistant bacteria.

Pharmacokinetics

Dicloxacillin is a beta-lactamase resistant penicillin similar to oxacillin. Dicloxacillin has in vitro activity against gram-positive and gram-negative aerobic and anaerobic bacteria. The bactericidal activity of dicloxacillin results from the inhibition of cell wall synthesis and is mediated through dicloxacillin binding to penicillin binding proteins (PBPs). Dicloxacillin is stable against hydrolysis by a variety of beta-lactamases, including penicillinases, and cephalosporinases and extended spectrum beta-lactamases.

Pharmacokinetics

Oral absorption: c. 50%
C_max , 250 mg oral: 9 mg/L after 1 h
500 mg intramuscular: 14–16 mg/L after 0.5–1 h
Plasma half-life: 0.5 h
Plasma protein binding: 95–97%
Absorption
Absorption in the very young is poor and unpredictable.
Metabolism and excretion
Dicloxacillin is partly metabolized in the liver and about 10% of the circulating drug is in the form of metabolites. Some 50–70% of a dose is excreted in the urine, about 20% as metabolites. It is eliminated both in the glomerular filtrate and by tubular secretion, and plasma concentrations are raised by probenecid. Parent drug and increased proportions of metabolites accumulate in renal failure. Elimination is increased through enhanced tubular secretion in patients with cystic fibrosis.

Pharmacology

In terms of mechanism of action, antibacterial spectrum, and indications for use, it is essentially no different than oxacillin and cloxacillin. Synonyms of this drug are diclocil, novapen, diclex, and others.
The following type of semisynthetic penicillins that should be considered are those in which amino acids, mainly α-aminophenylacetic or p-oxy-α-amino-phenylacetic acids, act as the acyl radical (ampicillin, amoxacillin).
The antimicrobial spectrum of aminopenicillins is similar to penicillin G, with the exception that they also act on a number of Gram-negative microorganisms. Both aminopenicillins are destroyed by staphylococcus penicillinase.

Side Effects

Phlebitis is common after intravenous injection. Its toxicity is otherwise similar to that of other penicillins. Clinical uses are those of the group 3 penicillins.

Metabolism

Not Available