dicloxacillin
Brand names: Dynapen
Dicloxacillin is an antibiotic that fights bacteria in your body. It belongs to a class of drugs called penicillinase-resistant penicillins.
Drug Pricing (NADAC)
Generic Price
$0.46/unit
Generic Available
Yes (2 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Dicloxacillin treats infections caused by certain staph bacteria that are resistant to penicillin.
Common side effects
Nausea, Vomiting, Diarrhea
Key warnings
Taking dicloxacillin with too little water or right before bed can cause burning, inflammation, or ulcers in your esophagus.
How It Works
Dicloxacillin works by stopping the growth of bacteria. It does this by interfering with the bacteria's ability to form cell walls. This weakens the bacteria and eventually kills them.
How to Take It
Take dicloxacillin on an empty stomach, at least 1 hour before or 2 hours after eating. Swallow the capsule with at least 4 ounces (120 mL) of water. Do not lie down immediately after taking this medicine. Follow your doctor's instructions on how much medicine to take and how often.
Pregnancy & Breastfeeding
Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. It is not known if dicloxacillin will harm an unborn baby. Small amounts of dicloxacillin may pass into breast milk.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store dicloxacillin capsules at room temperature, away from light and moisture.
Side Effects (from patient reports)
Based on 99 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 178 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
178
Death-Related Reports
20
Hospitalization Reports
69
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | SUSPECTED TRANSMISSION OF AN INFECTIOUS AGENT VIA PRODUCT | 13 |
| 2 | RASH | 12 |
| 3 | FATIGUE | 11 |
| 4 | PRURITUS | 11 |
| 5 | OFF LABEL USE | 10 |
| 6 | ABDOMINAL DISCOMFORT | 9 |
| 7 | DRUG INEFFECTIVE | 9 |
| 8 | BACK PAIN | 8 |
| 9 | DIARRHOEA | 8 |
| 10 | DRUG HYPERSENSITIVITY | 8 |
| 11 | DYSPNOEA | 8 |
| 12 | HEADACHE | 8 |
| 13 | NAUSEA | 8 |
| 14 | ACUTE KIDNEY INJURY | 7 |
| 15 | DEATH | 7 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Taking dicloxacillin with too little water or right before bed can cause burning, inflammation, or ulcers in your esophagus.
Known Drug Interactions
Dicloxacillin may reduce the anticoagulant response to dicumarol and warfarin.
Mechanism: Dicloxacillin can make warfarin less effective at thinning the blood.
What to do: Your doctor may need to check your blood clotting levels more often and adjust your warfarin dose.
Drug Interactions Tetracycline, a bacteriostatic antibiotic, may antagonize the bactericidal effect of penicillin and concurrent use of these drugs should be avoided.
Mechanism: Tetracycline stops bacteria from growing, which can prevent dicloxacillin from killing the bacteria effectively.
What to do: You should avoid taking these two antibiotics at the same time.
Probenecid administered concomitantly with penicillins increases and prolongs serum penicillin levels (see DOSAGE AND ADMINISTRATION ).
Mechanism: Probenecid slows down how fast the body gets rid of dicloxacillin, causing the drug to stay in the blood longer.
What to do: Your doctor may monitor you for side effects or adjust your dose since the drug levels in your body will be higher.
Common Questions
Can I take dicloxacillin with food?
What should I do if I experience side effects?
Can I take dicloxacillin if I am allergic to penicillin?
How long should I take dicloxacillin?
Can dicloxacillin interact with other medications?
What is the usual dose of dicloxacillin for adults?
What is the usual dose of dicloxacillin for children?
What should I do if I think I have taken too much dicloxacillin?
Can dicloxacillin cause diarrhea?
Is it safe to drive or operate machinery while taking dicloxacillin?
What are the common side effects of dicloxacillin?
Does dicloxacillin interact with other medications?
What drug class is dicloxacillin?
Is dicloxacillin safe during pregnancy?
Related Medications in Penicillinase-Resistant Penicillin
Other drugs grouped near dicloxacillin — same-class peers and common alternatives.
amikacin
Amikin
Amikacin is an antibiotic medicine.
Compare with dicloxacillin →
amoxicillin
Amoxil
Amoxicillin and Clavulanate Potassium is a combination medicine used to fight bacterial infections.
Compare with dicloxacillin →
amoxicillin/clavulanate
Augmentin
Augmentin is a combination of two medicines, amoxicillin and clavulanate.
Compare with dicloxacillin →
ampicillin/sulbactam
Unasyn
Unasyn is a combination of two antibiotics that fights bacteria in your body.
Compare with dicloxacillin →
azithromycin
Zithromax, Z-Pack
Azithromycin is an antibiotic that fights bacteria.
Compare with dicloxacillin →
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What the FDA Data Shows for dicloxacillin
The FDA label for dicloxacillin (sold under brand names such as Dynapen) classifies it as a prescription-only medication in the Penicillinase-Resistant Penicillin class. Dicloxacillin treats infections caused by certain staph bacteria that are resistant to penicillin. Official labeling lists 5 commonly reported side effects, including Nausea, Vomiting, Diarrhea.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 99 voluntary reports. The database also lists 3 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. NADAC pricing from CMS shows a generic unit cost of $0.46.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: October 15, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages