(amoxicillin trihydrate)

Brands

Amoxi-Drops (Amoxicillin Powder for Oral Suspension), Robamox (Amoxicllin Oral Tablets)

Availability

• Powder for suspension: 50 mg/mL
• Tablets: 50 mg, 100 mg, 200 mg, 400 mg

Pharmacology

A semisynthetic broad-spectrum penicillin, amoxicillin is a beta-lactam aminopenicillin. It differs structurally from ampicillin by having an additional hydroxyl group on the phenyl ring.

As with other penicillins, amoxicillin is a bactericidal, time-dependent, agent whose action inhibits cell wall synthesis. Amoxicillin tends to be better absorbed, orally, achieving higher serum levels than may be attained with ampicillin.

Amoxicillin is shown to be active against most strains of Gram-positive aerobes such as: Enterococcus faecalis, Streptococcus pneumoniae, and the alpha-hemolytic and beta-hemolytic strains of streptococcus. It is inactivated by beta-lactamase-producing bacteria such as Staphylococcus aureus, but has shown activity against beta-lactamase-negative strains of the Staphylococcus spp.

Amoxicillin also has increased activity against some strains of Gram-negative aerobes such as E. coli, klebsiella, haemophilus, and has shown some activity against anaerobic bacteria such as clostridial organisms.
Those organisms not generally susceptible to the aminopenicillins are: Pseudomonas aeruginosa, serratia, enterobacter, acinetobacter, citrobacter and also rickettsia, mycobacteria, fungi, mycoplasma, and viruses.

Amoxicillin is rapidly absorbed in the gastrointestinal tract and better absorbed orally, in animals, than is ampicillin. It is widely distributed into most tissues and fluids crossing into cerebrospinal fluid in the presence of inflamed meninges. Amoxicillin crosses the placenta and is found to be excreted in low concentration in breast milk. Even so, it is thought to be relatively safe to use during both pregnancy and lactation.

The drug is metabolized through the renal tubular structures and primarily excreted via the kidneys with small amounts being excreted in the feces and bile.

Indications

Useful in systemic infections, urinary tract infections, as well as skin and skin structure infections.

Drug Interactions or Contraindications

• Concomitant use of Probenecid will increase the plasma level of this antibiotic.
• Since in septicemia or shock gastrointestinal absorption is reduced it is advised to administer by parenteral route rather than oral.

Adverse Reactions

Blood: anemias

GI: anorexia, diarrhea

Other: hypersensitivity reaction such as rash and itching. Prolonged high doses can cause neurotoxicity. When given orally the penicillins may alter gut flora, selecting out resistant bacteria residing in the colon (leading to superinfections).

Dosage Recommendations

10 mg/lb, PO, BID  ⁴. Given over 10 to 21 days.

or

10 mg/kg to 15 mg/kg, PO, q12hr  ^41, 44

or

25 mg/kg, PO, q12hr  ^41, 44

or

20 mg/kg, PO, q24hr  ³⁵

or

10 mg/lb to 50 mg/lb, PO, BID  ^3, 12

or

100 mg/kg to 150 mg/kg, IM, SQ, q12hr  ^{, 41, 42, 44} (*Note: high dose use in more advanced illness, and cautiously per veterinarian’s decision.)

Considerations

• May give with food, does not significantly reduce absorption of drug.
• Give yogurt, Lactobacillus capsules/granules, or Bene-Bac to help maintain normal gut flora.
• In treating suspected polymicrobial infections, where a broader coverage may be needed, synergistic or combination drugs may be used. The following drugs may be seen used simultaneously with amoxicillin: Clavulanate, enrofloxacin (Baytril), or amikacin, or gentamicin. ¹
• Please note that it is imperative to discuss the changing or adding of any medications during your rat’s treatment with your veterinarian to prevent future resistance of microbes to the drugs prescribed.
• Store tablets and capsules at room temperature.
• Reconstituted oral suspensions are good for 14 days if refrigerated.

References

1. Amoxicillin (Amoxil®, Larotid®, Trimox®, Wymox®) Use by Pregnant & Lactating Women. (2001, November 19). Retrieved December 12, 2008, from https://www.fda.gov/cder/drugprepare/amoxicillinpreg.htm.
2. RxMed: Pharmaceutical Information – Amoxicillin. (n.d.). Retrieved December 12, 2008, from http://www.rxmed.com/b.main/b2.pharmaceutical/b2.1.monographs/CPS-%20Monographs/CPS-%20(General%20Monographs-%20A)/AMOXICILLIN.html.