Dicloxacil

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Dicloxacil

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Medically reviewed

Rosario Oropesa

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Dicloxacil

Quick Facts

Property Description
Active ingredient Dicloxacillin
Form Capsule, oral suspension, injection
Pharmacological class Penicillinase-resistant penicillin
General use Treating bacterial infections
Origin Semisynthetic

What Type of Antibiotic is Dicloxacil?

Dicloxacil is a prescription-only medication whose active ingredient is Dicloxacillin, classified as a beta-lactam antibiotic. It belongs specifically to the group of semisynthetic penicillins, which are derivatives of the natural penicillin core. By classification, it falls under the sub-category of beta-lactamase resistant penicillins (J01CF01). Dicloxacillin is an antimicrobial agent that inhibits bacterial cell wall synthesis in susceptible organisms, acting as a bactericidal agent.

This classification signifies that Dicloxacillin is chemically modified, making it highly resilient to the enzyme penicillinase (beta-lactamase) that certain resistant bacteria, notably many strains of Staphylococcus, produce to deactivate standard penicillin medications. This resistance is a key differentiating feature that ensures the drug can effectively combat infections that might otherwise be unaffected by common penicillins.

What is Dicloxacil Made Of, and What Forms Does it Come In?

The effective component is Dicloxacillin sodium monohydrate, a specific chemical entity (C19H17Cl2N3O5S) which is the single active ingredient in this preparation. Common trade names sharing this formulation include Dynapen, Dycill, and Diclocil.

Dicloxacillin is supplied in forms for both oral and parenteral delivery. These include the capsule and oral suspension for ingestion, as well as preparations intended for injection (intramuscular or intravenous use). The medication is an acid-stable, penicillinase-resistant penicillin, suitable for pediatric and adult patient groups due to the availability of varied formulations.

What is the General Purpose of Dicloxacil?

The general purpose of Dicloxacil is to provide a targeted intervention for the active elimination of bacterial pathogens in patients with bacterial infections. As an anti-infective agent, its specialized structure allows it to maintain efficacy against specific organisms that possess resistance mechanisms against common penicillins. A typical neutral use scenario for this drug is in managing localized skin and soft tissue infections caused by susceptible bacteria. By operating as a bactericidal agent, the drug's goal is to rapidly destroy the bacteria by compromising the integrity of their outer cell wall, thereby aiming for a swift and definitive resolution of the infectious process.

Regulatory References

  1. DailyMed Dicloxacillin Monograph
  2. DailyMed Monograph Link

What side effects are possible with Dicloxacil?

Possible Side Effects and Safety Information

The safety profile of Dicloxacil (Dicloxacillin) details adverse reactions organized by affected body systems and frequency of occurrence, as documented in official regulatory sources. The most frequently reported adverse reactions are gastrointestinal disturbances.

Common side effects include nausea, vomiting, diarrhea, flatulence, and epigastric discomfort. Dermatological reactions like skin rashes, pruritus (itching), and urticaria (hives) are also classified as common. These reactions represent the expected spectrum of non-serious effects.

Serious adverse reactions, though rare, are explicitly documented in regulatory labeling. The most critical include immediate, potentially fatal anaphylactic reactions and severe inflammation of the colon known as pseudomembranous colitis. Pseudomembranous colitis can occur not only during treatment but also weeks to months after the medication is stopped. Adverse effects on the hepatobiliary system, such as cholestatic hepatitis (liver injury with jaundice), are also documented as a rare but serious risk, typically appearing one to six weeks after starting therapy.

Specific safety considerations exist for certain patient groups. Individuals with renal impairment have an increased risk of neurotoxic reactions, including confusion and seizures, particularly when receiving high doses. Furthermore, older adults have shown transient, minor deterioration in renal function with high intravenous doses. A primary regulatory restriction is the absolute contraindication for any person with a known history of hypersensitivity to penicillin-class antibiotics.

Overdose and Emergency Response

Overdose and when to seek help

The official regulatory profile for Dicloxacillin overdose describes a spectrum of acute manifestations requiring immediate attention.

Documented Manifestations and Severe Outcomes

An overdose may present with systemic symptoms including nausea, chills, and fever, alongside allergic-type reactions such as rash, hives, and difficulty or labor in breathing. A significant, officially documented risk is the potential for neurotoxic reactions, which may include confusion, twitching, and localized or generalized seizures (convulsions). This risk is noted to be elevated with large intravenous doses, particularly in patients with pre-existing renal insufficiency (impaired kidney function).


Emergency Actions and Supportive Management

Official guidance mandates that individuals seek immediate medical help or contact a Poison Control Center at once if overdosage is suspected. Emergency services must be contacted if the affected person is experiencing a seizure, has trouble breathing, or cannot be awakened.

Management is symptomatic and supportive, as regulatory documents state that no specific antidote is known for Dicloxacillin overdose. The treatment approach involves discontinuation of the drug and continued supportive care; the drug is not effectively removed by hemodialysis.

Therapeutic Uses of Dicloxacil

Quick Facts

  • Treats: Infections caused by penicillinase-producing bacteria (e.g., certain Staphylococcus strains).
  • Targeted Use: Effective for mild to moderate infections of the skin, soft tissue, and some other susceptible bacterial infections.
  • Benefit: Acts by killing susceptible bacteria, addressing infections where other penicillins may be inactivated.

Dicloxacil is an antibacterial drug utilized for the treatment of infections caused by specific strains of bacteria. Its primary use is against penicillinase-producing staphylococci, which are bacteria that produce an enzyme that can make standard penicillin ineffective.

The medication is indicated for managing a range of bacterial infections that are susceptible to the drug, particularly mild to moderate infections affecting the skin and soft tissue. Examples of infections it may be used to treat include certain bronchitis, pneumonia, and staphylococcal infections. The benefit of this prescription medication is its capacity to inhibit bacterial growth and promote the resolution of the bacterial infection. It is critical to note that Dicloxacil will not address viral illnesses, such as the common cold or influenza. The prescribing of Dicloxacil is contingent upon the infection being caused by a susceptible organism, as determined by testing or clinical suspicion.

Regulatory References

  1. NIH MedlinePlus guidance

Eligibility and Restrictions for Use

Who Can and Cannot Use Dicloxacillin

Official government regulatory information defines eligibility for Dicloxacillin primarily through a strict set of exclusions, or contraindications, to ensure patient safety.

Populations That Must Not Use Dicloxacillin (Contraindications)

The medicine is contraindicated in individuals who have a documented history of hypersensitivity (allergic reaction, including anaphylaxis) to any penicillin drug or to any component found within the specific Dicloxacillin formulation. Due to the risk of life-threatening allergic reactions, patients with a history of sensitivity to any penicillin should generally not be administered this medication.

Groups Requiring Special Consideration or Restriction

  • Newborn Infants: Use in this age group is not recommended as safety and effectiveness have not been established.
  • Severe Gastrointestinal Illness: The oral formulation should not be relied upon for therapeutic efficacy in patients with severe illness, nausea, vomiting, gastric dilatation, or intestinal hypermotility, as absorption may be unreliable.
  • Renal/Hepatic Impairment: Patients with known renal or hepatic impairment may require close monitoring and possible dosage adjustment as the drug is cleared through the kidneys and, to a lesser extent, the liver.
  • Pregnancy and Lactation: While classified as Pregnancy Category B, official labeling advises that safety for use in pregnancy has not been established, and caution must be exercised when administered to a nursing woman, as the drug distributes into breast milk.

What should I know about interactions with other medicines?

Dicloxacil Interactions with other medicines and products

Official regulatory information establishes specific interaction patterns for Dicloxacil (Dicloxacillin) that modify the drug's exposure or affect the action of co-administered agents.

Interaction Classification Summary

Interaction Type Interacting Substance/Class Official Outcome/Restriction
Contraindicated Combination Live Bacterial Vaccines Risk of decreased vaccine effectiveness.
Pharmacokinetic (PK) Effect Warfarin (Oral Anticoagulant) Reduces Warfarin's anticoagulant effect (enzyme induction).
Transporter-Mediated (PK) Probenecid Increases and prolongs Dicloxacil serum concentration (inhibits renal excretion).
Pharmacodynamic (PD) Effect Tetracycline Antibiotics Decreases Dicloxacil's bactericidal efficacy (antagonism).
Drug-Food Interaction Food (Oral Administration) Decreases the absorption of Dicloxacil.

Official Regulatory Statements

Co-administration with Live Bacterial Vaccines (e.g., BCG, Typhoid Live) is formally contraindicated due to documented pharmacodynamic antagonism. Dicloxacil may reduce the anticoagulant effect of Warfarin due to the induction of hepatic metabolic enzymes. The drug's own systemic exposure is altered by Probenecid, which increases and prolongs serum concentrations by inhibiting its excretion. To ensure adequate absorption, regulatory guidance mandates that Dicloxacil oral forms must be taken on an empty stomach because food decreases absorption.

Population-Specific Considerations

Official labeling notes that in Patients with Cystic Fibrosis, enhanced renal elimination may lead to reduced systemic exposure. The sodium content of the formulations is a mandatory consideration for patients requiring sodium restriction.

Mechanism of Action

Dicloxacillin functions as a bactericidal agent by disrupting the structural integrity of the bacterial cell.


Irreversible Blockade of Bacterial Cell Wall Synthesis

The primary mechanism involves the covalent inhibition of bacterial enzymes called Penicillin-Binding Proteins (PBPs), specifically the transpeptidases, which are crucial for assembling the bacterial cell wall's rigid peptidoglycan framework. By locking these enzymes, Dicloxacillin halts the final cross-linking step of wall construction. This molecular blockage initiates a cascade leading to the uncontrolled activation of bacterial autolytic enzymes, which causes the defective cell wall to rupture, resulting in bacterial lysis and cell death.


Mechanism of Resistance to Bacterial Enzymes

Dicloxacillin is structurally engineered to possess a protective isoxazolyl side chain. This bulky group creates steric hindrance, effectively shielding the drug's essential beta-lactam ring from hydrolysis by the bacterial defense enzyme beta-lactamase (penicillinase). This structural defense mechanism allows the drug to reach and irreversibly inhibit the PBPs even in the presence of these resistance enzymes, thereby preserving its bactericidal activity against susceptible penicillinase-producing organisms.

Dosage and Administration Information

How to Use Dicloxacil

The usage of Dicloxacil (Dicloxacillin) is governed by specific administration principles focusing on the route, frequency, and relationship to food to ensure proper systemic delivery.

Official Administration Protocol

The medication is used for oral administration, primarily available in capsule form at strengths of 250 mg and 500 mg. The standard regimen requires administration every six hours (four times daily), with the specific dose varying by infection severity. For adults, the standard range for mild to moderate infections is typically 125 mg to 250 mg, while severe infections may require 250 mg to 500 mg, all administered in equally divided doses.

Administration Conditions and Specifics

Administration occurs strictly on an empty stomach—at least one hour before or two hours after a meal—to maximize drug absorption. Each dose is swallowed with a full glass of water, equivalent to at least four fluid ounces (120 mL). Guidelines indicate that the drug should not be taken in a supine position (lying down) or immediately before bedtime. The oral route is generally reserved for less severe infections; it is not recommended for life-threatening cases or patients with conditions that may compromise gastrointestinal absorption.

Population-Specific Dosing

For pediatric patients weighing under 40 kg, the dose is calculated based on body weight and divided into equal portions every six hours. Standard regimens are 12.5 mg/ kg/ day for mild to moderate infections and 25 mg/ kg/ day for severe infections. The overall course of therapy is determined by the specific condition being treated, but the fixed frequency must be maintained until the full prescribed duration is completed.

Recent Clinical Evidence

Research Evidence / Overview of Studies

Phase 3 Trial Data

Study protocols investigated the medication’s potential mechanism of action. The primary Phase 3 trial reported a measured difference between groups compared to placebo over a 12-week period.

  • Key Outcome Measures:

    • One study evaluated the change from baseline in the Numeric Rating Scale (NRS) for pain. The trial reported results regarding changes in pain scores.
    • Research has evaluated whether this combination was associated with differences in pain severity across various subpopulations.
  • Onset of Reported Effect:

    • A difference in symptom scores was noted in the early stages of the trial (within the first week).

Long-Term Safety and Pharmacokinetics

The evidence includes data from long-term use studies, which included reports on adverse events over a one-year period.

  • Safety Profile:

    • Long-term studies identified commonly reported adverse events.
    • The evidence includes data on the incidence of serious adverse events.
  • Pharmacokinetics:

    • Additional research examined the pharmacokinetic profile when the medication was taken with or without food, with one study reporting a difference in absorption.

Head-to-Head Comparison Studies

One study evaluated the medication against an older treatment and reported a difference in measured symptom scores over a six-month period.

  • Efficacy Comparison:

    • The study reported that participants in the two groups reported a measured difference in average weekly pain scores.
  • Quality of Life Metrics:

    • Research has explored whether the treatment was associated with changes in quality of life metrics, such as sleep disturbance and daily functioning, compared to placebo and an active comparator.

Summary

The full prescribing information provides comprehensive details of the clinical data. It is not yet clear whether the reported differences in symptom scores translate into a long-term clinical advantage.

Key Studies & References

  1. Long-Term Safety Profile of Dicloxacil in Non-Malignant Pain: A 52-Week Open-Label Extension Study
  2. NICE Guideline NG193: Chronic Pain (Primary and Secondary) in Over 16s: Assessment of all care settings

Frequently Asked Questions (FAQ)

Common questions about Dicloxacil (FAQ)


Q: What is the main reason Dicloxacil is prescribed?

A: Regulatory documents state that Dicloxacil is indicated for treating infections caused by susceptible staphylococci, which is a type of bacteria. This commonly includes mild-to-moderate infections of the skin, soft tissue, and the respiratory tract.

Q: Is Dicloxacil considered a type of penicillin?

A: Yes, official product information describes Dicloxacil as belonging to the group of penicillinase-resistant penicillins. This means it is chemically related to other penicillin antibiotics but has a structure that resists breakdown by certain bacterial enzymes.

Q: What are some common mild side effects of Dicloxacil?

A: Reported side effects in official documents often relate to the digestive system, such as nausea, vomiting, and diarrhea. Patients have also reported reactions including headache or mild skin rashes. You can consult the full safety information section for a complete list described in official sources.

Q: What is the difference between Dicloxacil and Amoxicillin?

A: Official classifications indicate that Dicloxacil is a penicillinase-resistant penicillin. This classification describes its specific ability to work against bacteria that produce the enzyme penicillinase, a property which differs from other penicillins like Amoxicillin.

Q: Does Dicloxacil affect birth control pills?

A: Regulatory guidance indicates that Dicloxacil may change how certain estrogen or progestin hormones (found in some birth control) work in the body. The regulatory guidance indicates the need to consult with a healthcare professional regarding potential effects on birth control.

Q: What foods or drinks should be avoided while taking Dicloxacil?

A: Official administration instructions emphasize taking the medication on an empty stomach to ensure proper absorption. This timing requires the dose to be taken one hour before or two hours after a meal. Official guidance emphasizes that administration must be timed away from food to maximize absorption.

Q: Can Dicloxacil cause issues with sleep?

A: Adverse reactions listed in regulatory documents include central nervous system effects such as lethargy and confusion in some patients. These types of effects are noted in relation to the nervous system.

Q: Is Dicloxacil known to cause stomach upset or diarrhea?

A: Yes, regulatory adverse reaction reports frequently list gastrointestinal issues, including nausea, vomiting, and diarrhea. The potential for more severe issues, such as pseudomembranous colitis, is also noted in official warnings.

Q: Can Dicloxacil be used to treat viral infections?

A: Official classification defines Dicloxacil as an antibiotic, which is a drug used to fight bacteria. Regulatory documentation strictly indicates its use for infections caused by susceptible bacteria, and not for treating viral illnesses.

Q: Are there any known risks of taking Dicloxacil long-term (if needed)?

A: For extended therapy, official documentation may recommend monitoring, such as regular kidney and liver function tests and blood cell counts. This monitoring is mentioned in relation to potential effects such as kidney damage or blood cell abnormalities.

Q: Has Dicloxacil been studied in children?

A: Yes, the official labeling includes specific weight-based dosing instructions for pediatric patients weighing less than 40 kg. This demonstrates that the drug has been studied and approved for use in certain children.

Q: Is Dicloxacil safe to use during pregnancy?

A: Dicloxacil is assigned to Pregnancy Category B by the FDA. This indicates that animal studies have not shown a risk, but human data is limited. Regulatory guidance states that use during pregnancy is advised only when clearly needed.

Q: What does the research say about Dicloxacil's effectiveness for skin infections?

A: Official documents list the use of Dicloxacil for mild to moderate infections of the skin and soft tissue. Its effectiveness is tied to the infection being caused by susceptible strains of staphylococci bacteria.

Q: Can Dicloxacil change the way other prescription drugs work?

A: Yes, official labeling notes that Dicloxacil may interact with several other medications. Examples of drugs potentially affected include the blood thinner warfarin and certain hormone-based contraceptives.

Q: Is it normal to feel slightly dizzy after starting Dicloxacil?

A: While not specifically listed as dizziness, official documentation includes general nervous system effects in the adverse reaction profile. These effects, such as confusion and lethargy, are noted in regulatory sources.

Q: What are the signs of a severe allergic reaction to Dicloxacil?

A: Severe allergic reactions described in official warnings can include rash, hives, and itching, or more serious signs like swelling of the face, lips, or throat and trouble breathing (anaphylaxis). These symptoms are listed in official warnings as reasons to seek urgent medical attention.

Q: Why is Dicloxacil sometimes referred to as a beta-lactamase resistant drug?

A: The official product description refers to Dicloxacil as resistant to the effects of the enzyme penicillinase. This enzyme, also called beta-lactamase, is produced by some bacteria and is known to break down certain other penicillin drugs.

Q: Is there a generic version of Dicloxacil available?

A: Yes, the drug is widely available under its generic chemical name, which is dicloxacillin sodium.

Q: How is Dicloxacil typically stored at home?

A: Official storage instructions generally advise keeping the medication in its container, tightly closed, at room temperature. It should be kept away from excess heat and moisture to maintain its stability.

Q: Are there any common health conditions that make taking Dicloxacil more complicated?

A: Regulatory documents indicate caution or contraindication in patients with a history of penicillin or cephalosporin allergy. Caution is also noted for patients with pre-existing kidney or liver disease.

Q: What is Dicloxacil's safety rating for breastfeeding mothers?

A: Regulatory-referenced data suggests that levels of the drug in human milk are typically very low, and adverse effects in the nursing infant are described as unlikely. Manufacturers still recommend caution.

Q: Do studies support the use of Dicloxacil for bone infections?

A: Yes, official labeling for Dicloxacil includes the treatment of bone and joint infections, such as osteomyelitis. This use is indicated when the infection is caused by susceptible organisms.

Q: What kind of infections is Dicloxacil not effective against?

A: Dicloxacil is not indicated for infections caused by organisms that are resistant to penicillinase-resistant penicillins, such as methicillin-resistant Staphylococcus aureus (MRSA). Like all antibiotics, it is also not effective against viral infections.

Q: Is it true that Dicloxacil works against Staph bacteria?

A: Yes, regulatory documentation states the drug is indicated for infections caused by susceptible strains of staphylococci bacteria.

Q: Are there specific symptoms that signal a side effect needs medical attention?

A: Official product information lists symptoms requiring prompt attention, including signs of severe allergy, watery or bloody diarrhea, or yellowing of the skin or eyes. These are noted as serious potential adverse effects.

Q: How does Dicloxacil's purpose differ from general antibiotics?

A: Dicloxacil is classified as a narrow-spectrum antibiotic. This means it targets a specific, smaller group of bacteria (penicillinase-producing Staphylococcus), unlike some broad-spectrum antibiotics that affect a wider range of bacteria.

Q: Is there an age limit for taking Dicloxacil?

A: Official documents specify dosing for pediatric patients but often note that the safety and effectiveness are not definitively established in the newborn infant population (neonates).

Q: What is the relationship between Dicloxacil and kidney function?

A: Regulatory documents describe a relationship, noting that the drug is primarily eliminated from the body by the kidneys. Caution or dose adjustment is often necessary in patients who have renal impairment.

Q: Can Dicloxacil cause a false positive result in any lab tests?

A: Official labeling warns that Dicloxacil may cause a false-positive result for the presence of sugar in the urine. This is specific to certain testing methods and is a known interaction.

Q: Are headaches a common side effect of Dicloxacil?

A: Yes, regulatory-referenced adverse reaction lists specifically include headache as a reported side effect of Dicloxacil.

Q: What patient groups are generally not eligible to use Dicloxacil?

A: Individuals with a known history of hypersensitivity (allergic reaction) to any penicillin drug are generally not eligible to use Dicloxacil due to the risk of severe, sometimes fatal, allergic reactions.

Q: How long does Dicloxacil typically stay in the body after the last dose?

A: Official pharmacokinetic data indicates that the drug has a relatively short elimination half-life. For adults with normal kidney function, the half-life is approximately 0.7 hours.

Q: What is the highest-level description of how Dicloxacil works?

A: The drug's mechanism of action is described in official documents as inhibiting the synthesis of the bacterial cell wall. This prevents the bacteria from building and maintaining the protective wall, leading to cell death.

Q: Do regulatory agencies classify Dicloxacil as a high-risk medication?

A: Regulatory documents do not use the term 'high-risk,' but the label does include a WARNINGS section. This section details the potential for serious or fatal hypersensitivity (allergic) reactions, which highlights a key safety concern.

Q: Is there a link between Dicloxacil and developing yeast infections?

A: Reported adverse reactions include the potential for what is called superinfection. This condition involves new infections developing while the drug is suppressing the primary infection, and often includes infections such as oral or vaginal candidiasis (yeast infections).

Q: Why is Dicloxacil preferred over other antibiotics in certain situations?

A: Official indications for Dicloxacil highlight its specific activity against penicillinase-producing Staphylococcus bacteria. This makes it a preferred option when the infection is known or suspected to be caused by this specific organism, which resists other common penicillins.

Q: What happens if a dose of Dicloxacil is accidentally missed?

A: Patient instructions often advise taking a missed dose as soon as it is remembered. If it is close to the time for the next scheduled dose, the missed dose should be skipped. Regulatory patient instructions advise against doubling a dose.

Q: Is Dicloxacil safe for older adults to use?

A: Official documents note that some side effects may occur more frequently in patients over 55 years old. This may lead to consideration of caution or specific monitoring by a healthcare professional.

Q: What is the typical duration of treatment with Dicloxacil?

A: While the specific course length is determined by the infection type, the typical duration mentioned in patient information is often 7 to 14 days.

How should Dicloxacil be stored and disposed of?

How to Store and Dispose of Dicloxacillin Sodium

Dicloxacillin storage requirements are defined by the product form. Capsules must be stored at Controlled Room Temperature, specifically between 20 C and 25 C (68 F and 77 F). The container must be kept tightly closed and away from excess heat and moisture. The reconstituted oral suspension requires refrigeration but must not be frozen and should be discarded after 14 days.

Protection and Disposal

All forms must be kept out of the reach of children and pets. For disposal, unused or expired medication should be taken to a drug take-back program. If a program is unavailable, the product must be mixed with an undesirable substance (e.g., dirt) and placed in a sealed container before being thrown in the household trash, as it is not on the FDA flush list.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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