STAPHCILLIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for STAPHCILLIN (STAPHCILLIN).

How it works

Semisynthetic penicillin; inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation, and activating autolytic enzymes.

What the body does with it

Metabolism	Hepatic and renal; primarily excreted unchanged in urine via tubular secretion; minor metabolism to inactive metabolites.
Excretion	Primarily renal (70-90% as unchanged drug via glomerular filtration and tubular secretion); minor biliary excretion (<5%) and fecal elimination (<1%).
Half-life	0.5-1 hour in adults with normal renal function; prolonged to 2-4 hours in renal impairment. Infants: 1-2 hours.
Protein binding	~20-30%, primarily to serum albumin.
Volume of Distribution	0.1-0.3 L/kg; indicates distribution primarily into extracellular fluid, with limited CNS penetration unless meninges inflamed.
Bioavailability	IM: 70-80%; oral: not available (acid-labile, must be parenteral).
Onset of Action	IM: 30-60 min; IV: immediate (peak after IV bolus).
Duration of Action	4-6 hours; may be extended in renal dysfunction. Bactericidal effect persists as long as serum concentrations exceed MIC.

Classification & Brands

Dosing & administration

1-2 g IV every 4-6 hours.

Dosage form	INJECTABLE
Renal impairment	CrCl 10-50 mL/min: 1-2 g every 6-8 hours; CrCl <10 mL/min: 1-2 g every 8-12 hours.
Liver impairment	No dosage adjustment required for mild to moderate hepatic impairment; severe impairment (Child-Pugh class C) use with caution.
Pediatric use	Infants and children: 25-50 mg/kg IV every 6 hours.
Geriatric use	Start at lower end of dosing range; monitor renal function and adjust based on CrCl.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for STAPHCILLIN (STAPHCILLIN).

Breastfeeding	Methicillin is excreted into breast milk in low concentrations. M/P ratio is unknown. It is considered compatible with breastfeeding, but monitor infant for potential gastrointestinal disturbances and allergic reactions.
Teratogenic Risk	Methicillin (STAPHCILLIN) is a penicillinase-resistant penicillin. No adequate and well-controlled studies in pregnant women. Animal studies have not demonstrated teratogenicity. However, potential risks include alteration of gut flora and rare hypersensitivity reactions. Use only if clearly needed.

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Serious Effects

Absolute Contraindications

["History of hypersensitivity to any penicillin","Neonates (controversial due to potential for kernicterus from bilirubin displacement)"]

Clinical Precautions

Precautions

["Serious hypersensitivity reactions including anaphylaxis","Clostridioides difficile-associated diarrhea","Superinfection with non-susceptible organisms","Use caution in renal impairment","Neurologic adverse effects with high doses"]

Clinical Tips & Counseling

Drug interactions

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STAPHCILLIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for STAPHCILLIN (STAPHCILLIN).

How it works

Semisynthetic penicillin; inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation, and activating autolytic enzymes.

What the body does with it

Metabolism	Hepatic and renal; primarily excreted unchanged in urine via tubular secretion; minor metabolism to inactive metabolites.
Excretion	Primarily renal (70-90% as unchanged drug via glomerular filtration and tubular secretion); minor biliary excretion (<5%) and fecal elimination (<1%).
Half-life	0.5-1 hour in adults with normal renal function; prolonged to 2-4 hours in renal impairment. Infants: 1-2 hours.
Protein binding	~20-30%, primarily to serum albumin.
Volume of Distribution	0.1-0.3 L/kg; indicates distribution primarily into extracellular fluid, with limited CNS penetration unless meninges inflamed.
Bioavailability	IM: 70-80%; oral: not available (acid-labile, must be parenteral).
Onset of Action	IM: 30-60 min; IV: immediate (peak after IV bolus).
Duration of Action	4-6 hours; may be extended in renal dysfunction. Bactericidal effect persists as long as serum concentrations exceed MIC.

Classification & Brands

Dosing & administration

1-2 g IV every 4-6 hours.

Dosage form	INJECTABLE
Renal impairment	CrCl 10-50 mL/min: 1-2 g every 6-8 hours; CrCl <10 mL/min: 1-2 g every 8-12 hours.
Liver impairment	No dosage adjustment required for mild to moderate hepatic impairment; severe impairment (Child-Pugh class C) use with caution.
Pediatric use	Infants and children: 25-50 mg/kg IV every 6 hours.
Geriatric use	Start at lower end of dosing range; monitor renal function and adjust based on CrCl.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for STAPHCILLIN (STAPHCILLIN).

Breastfeeding	Methicillin is excreted into breast milk in low concentrations. M/P ratio is unknown. It is considered compatible with breastfeeding, but monitor infant for potential gastrointestinal disturbances and allergic reactions.
Teratogenic Risk	Methicillin (STAPHCILLIN) is a penicillinase-resistant penicillin. No adequate and well-controlled studies in pregnant women. Animal studies have not demonstrated teratogenicity. However, potential risks include alteration of gut flora and rare hypersensitivity reactions. Use only if clearly needed.

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Serious Effects

Absolute Contraindications

["History of hypersensitivity to any penicillin","Neonates (controversial due to potential for kernicterus from bilirubin displacement)"]