Amoxicillin – Uses and Dosage

What is Amoxicillin?

Amoxicillin is the generic form of the brand-name drug Amoxil, a drug used to treat bacterial infections. Doctors prescribe amoxicillin to treat infections caused by bacteria that are sensitive to the drug, including E. coli, staphylococcus, streptococcus, H. influenzae, and H. pylori.

Amoxicillin belongs to a group of drugs called the penicillins. They originate from a form of fungi called Penicillium fungi. Penicillins are antibiotic drugs. It fights against bacteria and stops them from growing by preventing them from forming cell walls. This kills the bacteria and eventually eradicates the infection. Amoxicillin and other antibiotics are not known to be effective against viral infections, such as colds and flu.


Brand names

  • Amoxicot
  • Amoxil
  • Disper Mox
  • Moxatag
  • Moxilin
  • Trimox


  • Keep out of the reach of children.
  • Store between 68ºF and 77ºF (20ºC and 25ºC).
  • Keep bottle closed tightly.
  • Throw away any unused medicine after the expiration date.

Identity of Amoxicillin

Type of medicine Antibiotic
Synonyms Amox; AMC; Amoxicillin trihydrate; Amoxicillin anhydrous; Amoxycillin trihydrate; DAmoxicillin; p-Hydroxyampicillin
Molecular Formula C16H19N3O5S
Molecular Weight 365.404 g/mol
IUPAC Names (2S,5R,6R)- 6-{[(2R)-2-amino- 2-(4-hydroxyphenyl)- acetyl]amino}- 3,3-dimethyl- 7-oxo- 4-thia- 1-azabicyclo[3.2.0]heptane- 24-carboxylic acid
Structural formula of main components Amoxicillin chemical structure.png
Pure active ingredient Amoxicillin
Appearance Powder/Crystalline solid
Melting point 194°C
pH 4.4–4.9 (0.25% w/v solution)
Optical rotation +290°–315°
Solubility 3430 mg/L water
UVmax: 272 nm (water)
Partition coefficient -2.69
Stability to acids and bases Amoxicillin is stable in the presence of gastric acid
Bioavailability 95% by mouth
Excretion Kidneys
Density 1.6 ± 0.1 g/cm3
Used for Bacterial infections
Also called Clavulanic acid or Co-amoxiclav
Available as Tablet (Chewable & Extended Release), Capsule and Oral suspensions forms
Prescription Prescription Required

Amoxicillin Uses

Amoxicillin is a prescription antibiotic used in the treatment of the following:

  • Infections of the ear, nose, and throat
  • Infections of the reproductive organs
  • Infections of the urinary tract
  • Infections of the skin and skin structure
  • Infections of the lower respiratory tract
  • Gonorrhoea
  • Infection by pylori (type of bacterium) to reduce the risk of duodenal ulcer recurrence

This medication may be prescribed for other uses. Consult your doctor or pharmacist for more information.

Side Effects of Amoxicillin

Serious side effects are rare and happen in less than 1 in 1,000 people. Call a doctor straight away if you get:

  • Diarrhoea (possibly with stomach cramps) that contains blood or mucus. If you have severe diarrhoea for more than 4 days you should also speak to a doctor
  • Pale poo with dark pee, yellowing of the skin or the whites of your eyes (warning signs of liver or gallbladder problems)
  • Bruising or skin discolouration
  • Joint or muscle pain that comes on after 2 days of taking the medicine
  • A skin rash with circular red patches

Amoxicillin mono rash after infection.png

Amoxicillin mono rash after infection

Some of these serious side effects can happen up to 2 months after finishing the amoxicillin.

Mechanism of action

It works by interfering with the ability of bacteria to form cell walls.

  • The cell walls of bacteria are vital for their survival. They keep unwanted substances from entering their cells and stop the contents of their cells from leaking out.
  • Amoxicillin impairs the bonds that hold the bacterial cell wall together. This allows holes to appear in the cell walls and kills the bacteria.

Amoxicillin is a broad-spectrum antibiotic that kills a wide variety of bacteria that cause a wide variety of commonly-occurring infections.

To make sure the bacteria causing an infection are susceptible to amoxicillin your doctor may take a tissue sample, for example a swab from the throat or skin, or a urine or blood sample.

Susceptible Microorganisms 

Amoxicillin has been shown to be active against most strains of the following microorganisms:

Aerobic Gram-Positive Microorganisms:

  • Enterococcus faecalis
  • Staphylococcus spp. (β-lactamase-negative strains only)
  • Streptococcus pneumoniae
  • Streptococcus spp. (α- and β-hemolytic strains only)

Staphylococci which are susceptible to amoxicillin but resistant to methicillin/oxacillin should be considered as resistant to amoxicillin.

Aerobic Gram-Negative Microorganisms:

  • Escherichia coli (β-lactamase-negative strains only)
  • Haemophilus influenzae (β-lactamase-negative strains only)
  • Neisseria gonorrhoeae (β-lactamase -negative strains only)
  • Proteus mirabilis (β-lactamase -negative strains only)


Helicobacter pylori

Drug interaction with other medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary.

When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Chlortetracycline
  • Cholera Vaccine
  • Demeclocycline
  • Doxycycline
  • Lymecycline
  • Meclocycline
  • Methacycline
  • Methotrexate
  • Minocycline
  • Mycophenolate Mofetil
  • Oxytetracycline
  • Rolitetracycline
  • Sarecycline
  • Tetracycline
  • Venlafaxine
  • Warfarin

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Acenocoumarol
  • Khat
  • Probenecid

Other Interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Dosage of Amoxicillin

The drug dosage and form is decided by the physician based upon:

  • Age and body weight of the patient
  • Health status/medical condition of the patient
  • Disease severity
  • Reaction to the first dose
  • History of allergy/drug reactions
  • Tablets / suspensions

Amoxicillin tablets come in the following strengths:

  • 250 mg
  • 500 mg
  • A typical adult dosage is one 500-mg tablet of Amoxicillin every 12 hours or one 250-mg tablet every 8 hours.
  • The maximum dosage is maximum 1200 mg amoxicillin/kg/day

Dosage of Amoxicillin.png

Over dosage

Taking too much amoxicillin can cause dangerous effects in your child. These effects include kidney damage or kidney failure. The risk of these effects is another reason why you should follow the doctor’s dosage instructions exactly as prescribed.

If you think your child has taken too much amoxicillin, call your child’s doctor or your local poison control center right away. If your child’s symptoms are severe, go to the nearest emergency room or call 9-1-1. Symptoms of overdose can include:

  • Nausea
  • Vomiting
  • Diarrhoea
  • Pain in your child’s lower back


  • Before taking amoxicillin, tell your doctor or pharmacist if you are allergic to it; or to penicillin or cephalosporin antibiotics; or if you have any other allergies. This drug may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
  • Before using this medication, tell your doctor or pharmacist your medical history, especially of kidney disease, a certain type of viral infection (infectious mononucleosis).
  • Amoxicillin suspension may contain sugar. Caution is advised if you have diabetes or any other condition that requires you to limit/avoid sugar in your diet. Ask your doctor or pharmacist about using this drug safely.

Amoxicillin and Pregnancy

  • If you’re a woman, let your doctor know if you are or may be pregnant, are breastfeeding, or using birth control pills.
  • Though amoxicillin is widely believed to be safe, ask your doctor if the risks of taking antibiotics while pregnant outweigh the benefits.
  • Also, let your doctor know if you are breastfeeding because amoxicillin can pass through breast milk and increase the risk for a later allergic reaction in babies.

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