DYNAPEN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DYNAPEN (DYNAPEN).
Dynapen (dicloxacillin) is a penicillinase-resistant penicillin that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death.
| Metabolism | Hepatic metabolism to active and inactive metabolites; primarily excreted via renal tubular secretion and glomerular filtration. |
| Excretion | Renal: 60-80% as unchanged drug via glomerular filtration and tubular secretion; biliary/fecal: <10%. |
| Half-life | 0.5-1 hour in normal renal function; prolonged to 7-10 hours in anuria. |
| Protein binding | 80% primarily to serum albumin. |
| Volume of Distribution | 0.12-0.18 L/kg, indicating distribution primarily into extracellular fluid. |
| Bioavailability | Intramuscular: 70-80%; oral: not available. |
| Onset of Action | Intravenous: immediate (within minutes); intramuscular: 30-60 minutes. |
| Duration of Action | Intravenous: 2-4 hours; intramuscular: 4-6 hours. |
| Molecular Weight | 422.37 |
250-500 mg orally every 6 hours for skin and soft tissue infections; up to 500 mg every 6 hours for respiratory tract infections.
| Dosage form | FOR SUSPENSION |
| Renal impairment | CrCl 10-50 mL/min: administer every 8-12 hours; CrCl < 10 mL/min: administer every 12-18 hours. Hemodialysis: dose after dialysis. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment. Not studied in severe impairment; use with caution. |
| Pediatric use | Children >12 years: 250-500 mg orally every 6 hours; children <12 years: 12.5-25 mg/kg/day in divided doses every 6 hours. |
| Geriatric use | No specific adjustment for age alone. Monitor renal function; dose based on creatinine clearance. |
| 1st trimester | Avoid due to potential teratogenic effects (neural tube defects, congenital heart defects) based on animal studies and limited human data. |
| 2nd trimester | Use only if clearly needed, as there is no well-controlled human data; risk of nephrotoxicity and ototoxicity in fetus cannot be ruled out. |
| 3rd trimester | Use only if clearly needed; may cause neonatal hypotension, respiratory depression, or electrolyte disturbances if given near term. |
Clinical note
Comprehensive clinical and safety monograph for DYNAPEN (DYNAPEN).
| Placental transfer | Crosses placenta; achieves therapeutic levels in fetal serum and amniotic fluid. |
| Breastfeeding | Excreted into breast milk in low amounts; however, potential for infant renal toxicity and alteration of gut flora. Use with caution, especially in neonates or preterm infants. Monitor infant for diarrhea or rash. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to dicloxacillin or any penicillinHistory of allergic reaction to cephalosporins (cross-sensitivity)
| Precautions | Serious hypersensitivity reactions (anaphylaxis) can occur, especially in patients with a history of penicillin allergy., Patients with a history of cephalosporin allergy may cross-react., Clostridium difficile-associated diarrhea (CDAD) can occur., Use with caution in patients with renal impairment; dose adjustment may be necessary., Superinfection with resistant organisms may occur. |
| Food/Dietary | Food decreases the absorption of dicloxacillin. Avoid taking with meals; take on an empty stomach. No specific food restrictions otherwise. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but no adequate human studies. Generally considered low risk; however, use only if clearly needed. No known teratogenic effects in first, second, or third trimester. |
| Fetal Monitoring | No specific maternal-fetal monitoring required. Standard prenatal care. Monitor for maternal allergic reactions. |
| Fertility Effects | No known adverse effects on fertility. No impairment of fertility observed in animal studies. |
| Clinical Pearls | Dynapen (dicloxacillin) is a penicillinase-resistant penicillin indicated for infections caused by beta-lactamase-producing staphylococci. It is not effective against methicillin-resistant Staphylococcus aureus (MRSA). Administer on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption. Monitor for hypersensitivity reactions, especially in patients with penicillin allergy. Use with caution in patients with renal impairment; dose adjustment may be needed. |
| Patient Advice | Take this medication on an empty stomach, at least 1 hour before or 2 hours after a meal. · Complete the full course of treatment even if you feel better. · Inform your doctor if you have a history of penicillin allergy or allergic reactions. · Report any signs of allergic reaction: rash, itching, swelling, difficulty breathing. · Avoid alcohol while taking this medication. |