DICLOXACILLIN SODIUM
Clinical safety rating: safe
Human studies have proved safety
Dicloxacillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), thereby inhibiting transpeptidation and leading to cell lysis. It is resistant to penicillinase-producing organisms.
| Metabolism | Hepatic metabolism (minor); primarily excreted unchanged by renal tubular secretion. |
| Excretion | Primarily renal: ~60-85% unchanged via glomerular filtration and tubular secretion; ~10% hepatobiliary (bile) and fecal; minor metabolism to penicilloic acid. |
| Half-life | Terminal elimination half-life: 0.6-0.8 hours in adults with normal renal function; prolonged to 1-2 hours in neonates, elderly, or severe renal impairment. |
| Protein binding | 95-98% bound to serum albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.1-0.2 L/kg; low distribution primarily to extracellular fluid; poor penetration into CSF (except inflamed meninges). |
| Bioavailability | Oral: 35-76% (extensive first-pass metabolism; take on empty stomach). IM: ~80-90%. |
| Onset of Action | Oral: ~1 hour (peak serum concentration). Intramuscular: 0.5-1 hour. Intravenous: Immediate. |
| Duration of Action | 6-8 hours (dosing q6h recommended); bactericidal concentration maintained for 4-6 hours post-dose. |
125-500 mg orally every 6 hours
| Dosage form | FOR SUSPENSION |
| Renal impairment | No adjustment required for mild to moderate renal impairment; for GFR <10 mL/min, maximum dose 500 mg/day |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 25-50%; Child-Pugh C: avoid use or reduce dose by 50-75% |
| Pediatric use | 12.5-25 mg/kg/day orally divided every 6 hours; maximum 500 mg/day |
| Geriatric use | No specific dose adjustment; monitor renal function and adjust if impaired |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Probenecid may decrease excretion Serious and occasionally fatal hypersensitivity reactions have been reported.
| Breastfeeding | Dicloxacillin is excreted into breast milk in small quantities. The milk-to-plasma ratio (M/P) is approximately 0.08-0.14. The American Academy of Pediatrics considers dicloxacillin compatible with breastfeeding. However, theoretical risks include alteration of infant gut flora, diarrhea, or allergic sensitization. Monitor infant for gastrointestinal disturbances. |
| Teratogenic Risk | Dicloxacillin is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and there are no adequate and well-controlled studies in pregnant women. As a penicillinase-resistant penicillin, it is generally considered low risk for teratogenicity across all trimesters. No specific fetal abnormalities have been consistently associated with exposure. |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | Diarrhea |
| Serious Effects |
["History of hypersensitivity to penicillins or cephalosporins","History of dicloxacillin-associated cholestatic jaundice/hepatic dysfunction"]
| Precautions | ["Hypersensitivity reactions including anaphylaxis","Clostridioides difficile-associated diarrhea (CDAD)","Prolonged use may lead to superinfection","Use caution in patients with renal impairment requiring dose adjustment"] |
| Food/Dietary | Dicloxacillin absorption is significantly reduced by food, especially high-fat meals. Take on an empty stomach with a full glass of water. Avoid food for 1 hour before and 2 hours after dosing. No other specific food interactions reported. |
Loading safety data…
| Fetal Monitoring | No specific maternal or fetal monitoring is required beyond standard pregnancy care. For prolonged therapy, monitor maternal renal function and signs of hypersensitivity. If treating infections in pregnancy, clinical response should be assessed. No fetal monitoring indicated. |
| Fertility Effects | No known adverse effects on fertility in males or females based on animal studies and clinical data. Dicloxacillin does not impact reproductive hormones or gamete function. No fertility impairment reported. |
| Clinical Pearls | Dicloxacillin is acid-stable and penicillinase-resistant, making it first-line for methicillin-susceptible Staphylococcus aureus (MSSA) skin infections. Take on an empty stomach (1 hour before or 2 hours after meals) because food reduces absorption by up to 50%. Monitor liver function tests in prolonged therapy; can cause elevated transaminases or cholestatic hepatitis. Use with caution in renal impairment (CrCl <10 mL/min) due to risk of neurotoxicity (seizures) from accumulation. Not active against MRSA; consider vancomycin or other agents if MRSA suspected. |
| Patient Advice | Take dicloxacillin on an empty stomach: at least 1 hour before or 2 hours after meals. · Complete the full course of treatment even if you feel better to prevent antibiotic resistance. · Do not skip doses; if you miss a dose, take it as soon as possible but do not double up. · Common side effects include nausea, vomiting, diarrhea, and skin rash. Contact your doctor if you experience severe diarrhea, jaundice, or signs of an allergic reaction (hives, swelling, difficulty breathing). · This medication may cause false-positive results on urine glucose tests (if using Clinitest). Inform your doctor if you have diabetes. · Store at room temperature, away from moisture and heat. |