Uses and Side Effects of Dicloxacillin

This is a medicine used to fight bacterial infections. It's prescribed for adults and children over 12 years of age. How does it work and what are the side effects of Dicloxacillin? We'll tell you what you need to know in the article below.
Uses and Side Effects of Dicloxacillin
Fabiola Marín Aguilar

Written and verified by the pharmacist Fabiola Marín Aguilar.

Last update: 27 May, 2022

Dicloxacillin is a beta-lactam antibiotic belonging to the penicillin and penicillin-resistant group. The latter refers to enzymes that certain micro-organisms produce, which are capable of hydrolyzing and inactivating penicillin. In this article, we’ll tell you when doctors may prescribe this medication as well as the possible side effects of dicloxacillin.

Dicloxacillin is useful for treating infections caused by gram-positive bacteria, such as Staphylococcus aureus. It’s also effective in treating infections caused by group A streptococci such as Streptococcus pneumoniae.

A bit of history

The first antibiotic to be widely used in medicine was penicillin G or benzylpenicillin. Alexander Fleming discovered it in 1928, for which he won a Nobel Prize. Since then, advances in science have enabled the development of new molecules for the specific treatment of various bacterial infections.

Today, there are different groups of beta-lactams, in addition to penicillin G. These include ampicillin, amoxicillin, or penicillin-resistant penicillins, such as dicloxacillin, which we’re discussing in this article.

A hand with a glove removing liquid from a bottle with a needle and syringe.
In addition to penicillin G, there are other beta-lactam antibiotics such as ampicillin, amoxicillin or penicillin-resistant penicillins, such as dicloxacillin.

Therapeutic indications of penicillins

Doctors prescribe dicloxacillin for adults and children over 12 years of age, in the treatment of the following bacterial infections:

  • Acute streptococcal pharyngo-tonsillitis
  • Skin infections and related structures such as scarlet fever, impetigo, or boils
  • Infections of the dental and periodontal structures

The dosage and duration of treatment will depend on the type of condition that requires treatment.

Mechanism of action

The mechanism of action of penicillin has to do with the activation of enzymes that alter the cell wall of bacteria by acting as a bactericide. In other words, they destroy the bacteria.

Some warnings and precautions for use

It’s important that before starting treatment with dicloxacillin, you notify your doctor if you’ve ever had an allergic reaction to penicillin or other beta-lactams. Like most antibiotics, dicloxacillin can lead to diarrhea or pseudomembranous colitis due to Clostridium difficile.

You may also want to read: How to Tell if the Gut Microbiota is Damaged

Can dicloxacillin interact with other medicine?

When taking dicloxacillin, you should be aware that, as we’ve already mentioned, dicloxacillin is a penicillin. Research has revealed that penicillins can reduce the excretion of methotrexate when patients take them together. This reduction in the excretion of the drug can lead to an increase in its toxicity.

In addition, penicillins can interact with oral contraceptives, decreasing their effectiveness and, therefore, increasing the risk of pregnancy.

Pregnancy, lactation, and dicloxacillin

To date, clinical experience seems to indicate little risk to pregnancy, the fetus, or the newborn baby. However, doctors should conduct a risk/benefit assessment before prescribing dicloxacillin as treatment.

In the case of breastfeeding, it appears that there’s a very low rate of excretion of penicillin in breast milk. Therefore, it’s unlikely that the baby will experience any harmful effects. Just the same, a doctor’s risk/benefit assessment is most advisable.

Having said that, doctors often use dicloxacillin to treat mastitis in breastfeeding mothers. And sometimes this may affect the baby’s oral and intestinal microbiota, leading to episodes of diarrhea.

However, this effect seems to lack adequate research and penicillin treatment during breastfeeding continues to be compatible.

A doctor with a pill bottle in his hands talking to a pregnant patient.
The use of dicloxacillin in pregnancy is considered safe. To date, there’s no research showing that it causes any relevant risks to the mother or the fetus.

Side effects of dicloxacillin

The adverse effects of dicloxacillin and antibiotics in general mainly include gastrointestinal disorders, such as the following:

  • Nausea
  • Vomiting
  • Diarrhea
  • Flatulence
  • Epigastric pain and even halitosis

In addition, like other penicillins, it can produce allergic symptoms such as hives, itching, rash, or an anaphylactic reaction in the case of a severe allergy.


It’s important to note that antibiotics are prescribed in the treatment of bacterial infections but aren’t effective in cases of viral infections.

For this reason, the use of antibiotics to treat a cold, flu, or any other virus won’t be effective and there’s a risk of creating resistance. Always consult your doctor.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.