Amoxicillin

Oral Antibiotics

Drug class: β-Lactam Antibiotics, belonging to the aminopenicillin class of the penicillin family

Amoxicillin (AMOXIL)（中文：阿莫西林）

Common Strengths of Amoxicillin

Amoxicillin are available in the following strengths:

• 250 mg
• 500 mg
• 875 mg (extended-release)
• Available in liquid formulations (e.g. 125 mg/5 mL, 200 mg/5 mL, 400 mg/5 mL) for pediatric use.

Drug Trade Name of Amoxicillin

Amoxil

Drug Usage

Amoxicillin is prescribed for treating infections caused by susceptible bacteria, including:

• Respiratory tract infections (e.g. pneumonia, bronchitis)
• Ear, nose, and throat infections (e.g. otitis media, tonsilitis)
• Skin infections
• Urinary tract infections
• Helicobacter pylori eardication in combination therapies for peptic ulcers

Mechanism of Action

Amoxicillin works by inhibiting bacterial cell wall synthesis, leading to cell lysis and death. It is effective against a range of gram-positive and some gram-negative bacteria.

Route of Administration

• Oral (tablets, capsules, liquid suspension)
• Intramuscular injection
• Intravenous (IV) bolus injection

Dosages

• Typically 500 mg every 12 hours or 250 mg every 8 hours.
• Renal Impairment: Dosage adjustments are necessary based on estimated Glomerular Filtration Rate (eGFR):
  • eGFR >30 mL/min: No adjustment needed.
  • eGFR 10-30 mL/min: 250 mg every 12 hours.
  • eGFR <10 mL/min: 250 mg every 24 hours.

Side Effects

Frequency	Adverse reactions
Common Side Effects	Diarrhea, nausea, vomiting, rash, headache, and yeast infections.
Serious Side Effects	Allergic reaction (anaphylaxis)
	Severe skin reactions (Stevens-Johnson syndrome)
	Liver dysfunction
	Clostridium difficile-associated diarrhea

Pharmacokinetics

• Bioavailability: Approximately 95% when taken only.
• Peak Concnetrations: After oral administration, peak serum concentrations typically occur 1 to 2 hours post-dose.
• Half-Life: The elimination half-life of amoxicillin is about 1 hour, which is relatively short. This necessitates multiple dosing throughout the day to maintain effective therapeutic levels.
• Excretion: About 60% of an orall administered dose is excreted unchanged in the urine within 6 to 8 hours.
• Onset of Action: Typically within 1-2 hours.
• Duration: Effects can last 8-12 hours, necessitating multiple doses per day.

Drug Precautions

Pregnancy

Generally considered safe; however, consult a doctor.

Breastfeeding

Excreted in breast milk; caution is advised.

Children and Elderly

Safe for use in children; elderly patients may require dosage adjstments based on renal function.

Monitoring Requirements

Regular monitoring of renal function, liver enzymes, and signs of severe allergic reactions is recommended.

Drug Interactions

• Anticoagulants: Amoxicillin can enhance the effects of anticoagulants like warfarin, leading to an increased risk of bleeding.
• Allopurinol: When taken together, amoxicillin and allopurinol may increase the incidence of skin rashes.
• Methotrexate: Amoxicillin may interfere with the elimination of methotrexate, potentially increasing its toxicity.
• Oral Contraceptives: Amoxicillin can affect gut flora, potentially leading to reduced efficacy of combined oral contraceptives. Patients using hormonal contraceptives should be informed about this risk and consider additional contraceptive measures during amoxicillin therapy.
• Food Interactions: While food dose not significantly affect the absorption of amoxicillin, it is generally advised to take it with food to minimize gastrointestinal side effects.

FAQ

How Should I Take the Tablet?

Swallow whole' chewable tablets should be chewed thoroughly. Liquid forms can be mixed with cold beverages.

What Should I Avoid While Taking?

Avoid alcohol and inform your doctor of any other medications, especially hormonal contraceptives.

What Happens if I Miss a Dose?

Take the missed dose as soon as remembered unless it is close to the next dose. Do not double up on doses.