Amoxicillin is the most commonly prescribed antibiotic in the UK, with over 6 mln prescriptions issued in the last 12 months. Flucloxacillin is less prevalent, with around 3.6 mln prescriptions published simultaneously (OpenPrescribing.net, 2021).
Both antibiotics’ distinct popularity comes mainly from recommended use in the treatment of bacterial infections, even though both drugs belong to the same class of antibiotics: penicillins. This post focuses on highlighting the main differences between drugs.
Flucloxacillin vs. Amoxicillin: legal classification
Both drugs are classified as prescription-only medicines (POM), and with this, Amoxicillin and flucloxacillin need to be prescribed by a qualified doctor, dentist, or another qualified prescriber.
Dentists, however, cannot prescribe flucloxacillin on NHS prescriptions. Flucloxacillin is not listed as medicines allowed on the FP10D type of NHS prescription.
Licensed use of flucloxacillin and Amoxicillin
In the UK, flucloxacillin is a preferable antibiotic in treating skin infections and is usually reserved for this use. Flucloxacillin is almost ‘exclusively’ used to treat skin and soft tissue infections (Francis et al., 2016).
The difference in the licensed use between flucloxacillin and Amoxicillin is the main driving factor for significant variation in prescribing both drugs.
| Amoxicillin | Flucloxacillin |
|---|---|
| Otitis media | Skin and soft tissue infections including: boils, cellulitis, infected burns abscesses. |
| Bacterial sinusitis | Impetigo |
| Streptococcal tonsillitis and pharyngitis | Skin infections in acne, ulcers, eczema |
| Chronic bronchitis: Acute exacerbations | Protection for skin grafts |
| Community acquired pneumonia | Carbuncles |
| Cystitis | Furunculosis |
| Asymptomatic bacteriuria in pregnancy | Infected wounds |
| Acute pyelonephritis | Otitis media and externa |
| Typhoid and paratyphoid fever | Pneumonia |
| Dental infections | Lung abscess |
| Prosthetic joint infections | Empyema |
| Helicobacter pylori eradication | Sinusitis |
| Lyme disease | Pharyngitis, tonsillitis and quinsy |
| Prophylaxis of endocarditis | Osteomyelitis, urinary tract infection, enteritis, meningitis, endocarditis and septicaemia |
Why Is Flucloxacillin Recommended Antibiotic For Skin Infections?
Flucloxacillin is classified as a narrow-spectrum antibiotic. It is effective against infections caused by a limited number of bacteria, particularly Staphylococcus aureus, which commonly cause bacterial skin infections. Broad-spectrum antibiotics, such as Amoxicillin, may offer treatment against a wider group of bacteria.
The main disadvantage of broad-spectrum antibiotics is the potential to contribute to bacterial resistance across different bacteria types (Melander et al., 2017).
Flucloxacillin vs Amoxicillin: Different Formulations
In the community, flucloxacillin and amoxicillin are usually prescribed in the form of capsules(adults) or as a powder for oral suspensions, when used to treat infections in children.
The table below list all formulations available for both drugs:
| Flucloxacillin | Amoxicillin |
|---|---|
| Capsules | Capsules |
| Powder for oral suspensions | Powder for oral suspensions |
| Powder for injections | Powder for injections |
| Sachets and dispersible tablets |
Child Formulations For Flucloxacillin And Amoxicillin
Both flucloxacillin and Amoxicillin are available as powders for oral suspensions, usually prescribed to treat infections in children. When a prescription is brought into the pharmacy for one of the antibiotics, a certain amount of water is added during the dispensing process.
Mixing of antibiotics powder is done by a pharmacy team unless instructed otherwise. Storage instruction for both antibiotics may be different. Generally, many made-up oral antibiotics need to be kept in the fridge.
Read about the storage requirements on the box. I also dedicated a separate cost for children’s storage and expiry dates of liquid antibiotics.
Quick FAQ
Differences In Administration
I will not go into the details for recommended administration methods for each antibiotic. Amoxicillin is generally taken three times a day, whereas flucloxacillin is four times a day. This dosing is not a general rule. Follow the directions of your prescriber.
Perhaps one of the most important differences between both drugs is the administration in relation to food stomach content.
- Flucloxacillin should be taken on an empty stomach. This means one hour before food or two hours after food.
- Amoxicillin can be taken on an empty stomach or with food. The absorption of Amoxicillin is not affected by food (eMC, 2020).
Flucloxacillin vs. Amoxicillin: Common Side Effects
| Flucloxacillin | Amoxicillin |
|---|---|
| Diarrhoea & stomach upset | Diarrhoea |
| Nausea (feeling sick) | Nausea (feeling sick) |
| Heartburn and indigestion | Skin rash |
Source: Product information leaflets for flucloxacillin and Amoxicillin.
Gastrointestinal side effects such as upset stomach, diarrhea, and feeling sick are usually mild and may disappear after a few days.
Use Of Flucloxacillin And Amoxicillin In The Pregnancy
Penicillins can be used in pregnancy. They are not known to be harmful (Joint Formulary Committee, 2019).
Who Should Not Take Flucloxacillin Or Amoxicillin
Patients should not take flucloxacillin and Amoxicillin with suspected or known sensitivity to penicillins. Patients should not take flucloxacillin with a history of liver problems (liver dysfunction or jaundice).
Prescribing Statistics And Seasonality
When looking at prescribing trends for both antibiotics, it can be easily seen that there is seasonality to prescribing for both drugs. Amoxicillin prescribing peaks during the winter (December-January), whereas flucloxacillin during summer (June to August).
The reason behind seasonality is preferred use in different infection types. Amoxicillin would be the first choice in respiratory infections (infections peak in the winter), one the other hand, as already discussed, flucloxacillin would be the first choice in the skin and soft tissue infections, for example, caused by infected insect bites (peak in the summer months).
Quick FAQ
Alternative Treatment Options
Plenty of antibiotics is available on the market, including different oral antibiotics and antibiotic creams. However, each antibiotic has its licensed use and is prescribed according to national and local guidelines.
Antibiotic resistance is one of the critical public health concerns. The resistance of bacteria to the treatment means that antibiotics stop being effective.
Looking for more answers? Leave the comment below, and I will try to answer your question.