DYCILL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DYCILL (DYCILL).
Penicillin G benzathine is a slow-release parenteral formulation of penicillin G that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation, and activating autolytic enzymes.
| Metabolism | Penicillin G is metabolized by hydrolysis to penicilloic acid (inactive) via bacterial and possibly hepatic penicillinases. Approximately 60-90% of an IM dose is excreted unchanged in the urine within 24-48 hours. |
| Excretion | Renal: approx. 60-80% unchanged by glomerular filtration and tubular secretion. Biliary/fecal: minor (less than 10%). |
| Half-life | 0.5-1 hour; prolonged in renal impairment (up to 20 hours in severe cases). |
| Protein binding | 50-60% primarily to serum albumin. |
| Volume of Distribution | 0.3-0.4 L/kg; distributes into interstitial fluid, low CNS penetration. |
| Bioavailability | Oral: 25-40% (acid-labile, food reduces absorption). IM: nearly 100%. |
| Onset of Action | Oral: 30-60 min; IM: 15-30 min. Rapid bactericidal effect. |
| Duration of Action | 6-8 hours for oral; 12-24 hours after IM. Prolonged in renal failure. |
250 mg orally every 6 hours or 500 mg orally every 12 hours.
| Dosage form | CAPSULE |
| Renal impairment | CrCl 10-50 mL/min: 250 mg every 12-24 hours. CrCl <10 mL/min: 250 mg every 24-36 hours. |
| Liver impairment | No adjustment required for mild-moderate impairment. Severe (Child-Pugh C): consider 250 mg every 12 hours. |
| Pediatric use | Children >12 years: same as adult. Children 1-12 years: 15-25 mg/kg/day divided every 6-8 hours. |
| Geriatric use | Start at lower end of dosing range (250 mg every 12 hours) due to potential renal impairment; monitor renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DYCILL (DYCILL).
| Breastfeeding | Dicloxacillin is excreted into breast milk in small amounts (estimated M/P ratio approximately 0.1-0.2). The concentration is unlikely to cause adverse effects in the infant, but potential for gastrointestinal disturbance or sensitization exists. The American Academy of Pediatrics considers dicloxacillin compatible with breastfeeding. Use with caution in infants with history of penicillin allergy. |
| Teratogenic Risk | Dycill (dicloxacillin) is a penicillinase-resistant penicillin classified as Pregnancy Category B. Animal studies have not demonstrated fetal risk, and there are no adequate well-controlled studies in pregnant women. First trimester: No evidence of teratogenicity, but use only if clearly needed. Second and third trimesters: No documented fetal harm, but caution due to potential alteration of gut flora. Overall, risk is low, but idiosyncratic reactions cannot be excluded. |
■ FDA Black Box Warning
WARNING: Not for intravenous use. Inadvertent intravenous administration of penicillin G benzathine has resulted in cardiorespiratory arrest and death. Do not inject intravenously or admix with other intravenous solutions. Administer only by deep intramuscular injection.
| Serious Effects |
Hypersensitivity to penicillins or any component of the formulation; history of severe immediate hypersensitivity reaction (e.g., anaphylaxis) to other beta-lactam antibiotics (e.g., cephalosporins, carbapenems).
| Precautions | Severe hypersensitivity reactions (anaphylaxis) can occur; administer only if appropriate treatment for anaphylaxis is available. Use caution in renal impairment (dose adjustment needed for CrCl <10 mL/min). Caution in patients with history of asthma, allergies, or seizure disorders. Risk of Clostridioides difficile-associated diarrhea. Prolonged use may lead to superinfection. Periodic renal, hepatic, and hematologic monitoring recommended with high doses. |
| Food/Dietary | Avoid high-fat meals or large amounts of food within 1 hour before or 2 hours after dosing as they significantly reduce absorption. Acidic beverages (fruit juices) may also affect absorption. No specific dietary restrictions beyond timing of meals. |
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| Fetal Monitoring | Routine monitoring: No specific fetal monitoring required. For prolonged therapy or high doses, monitor maternal renal function and signs of superinfection. In the neonate, observe for diarrhea, rash, or candidiasis. No need for serum drug level monitoring in pregnancy. |
| Fertility Effects | No established effects on fertility in animal models. Dicloxacillin does not affect spermatogenesis or oogenesis. No known impact on conception or implantation. Use during fertility treatments is not contraindicated. |
| Clinical Pearls | DYCLL is a brand name for dicloxacillin, a penicillinase-resistant penicillin used for staphylococcal infections. Ensure adequate renal function as dose adjustment is needed in severe renal impairment (CrCl <10 mL/min). Administer on an empty stomach (1 hour before or 2 hours after meals) since food reduces absorption by up to 50%. Use with caution in patients with cephalosporin allergy due to possible cross-reactivity. Monitor for signs of hypersensitivity, especially skin rash and anaphylaxis. Not effective against methicillin-resistant Staphylococcus aureus (MRSA). |
| Patient Advice | Take dicloxacillin on an empty stomach, at least 1 hour before or 2 hours after meals, with a full glass of water. · Complete the full course of therapy even if you feel better; do not stop early. · Report any signs of allergic reaction immediately: rash, itching, swelling, severe dizziness, trouble breathing. · May cause diarrhea; if severe, persistent, or containing blood/mucus, contact your doctor. · Store capsules at room temperature away from moisture and heat. · Do not use for viral infections (like colds or flu) as it is ineffective. |