The Navigation Model of Therapy: Why Awareness Changes Everything
November 16, 2025
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Brand Name :
Dimocillin / Metacillin
Synonyms :
Methicillin
Class :
Penicillinase Resistant Penicillin's
Brand Name :
Dimocillin / Metacillin
Synonyms :
Methicillin
Class :
Penicillinase Resistant Penicillin's
Dosage Forms & Strengths
SolutionÂ
500 mg/vialÂ
1 g (1000 mg)/vialÂ
5 g/vial Â
Adult dosingÂ
4–6 g/day IV or IM, divided into four to six doses (every 4–6 hours).Â
Severe infections
Up to 10–12 g/day IV in divided doses may be used, depending on severity and site of infection.Â
InfectionsÂ
Children >1 month
100–200 mg/kg/day IV or IM, divided every 4–6 hours.Â
Neonates (<1 month)
Limited data; generally 50–100 mg/kg/day, adjusted per weight, age, renal function.Â
Refer adult dosing
Action and Spectrum:
Methicillin is a type of antibiotic that belongs to the beta-lactam class of antibiotics. It works by inhibiting the synthesis of the bacterial cell wall, which leads to the death of susceptible bacteria.
The spectrum of methicillin is narrow and it is primarily effective against staphylococcal infections, particularly those caused by Staphylococcus aureus. It is not effective against other types of bacteria, such as gram-negative bacteria.
Methicillin is also known for its resistance to the beta-lactamase enzyme, which is produced by some bacteria to break down beta-lactam antibiotics like penicillin. This makes methicillin a useful antibiotic for treating infections caused by beta-lactamase-producing bacteria.
Frequency not defined
Seizures
Fever
Decreased WBC count
Black Box Warning:
methicillin is no longer commercially available and has been discontinued for clinical use. However, other antibiotics in the same class, such as penicillin, amoxicillin, and other beta-lactam antibiotics, may have similar black box warnings.
The black box warning for beta-lactam antibiotics is related to the risk of anaphylaxis, which is a severe allergic reaction.
Contraindication / Caution:
methicillin, like other antibiotics, has several contraindications and precautions that should be taken into consideration before administering it. These include:
Allergy to Methicillin or other beta-lactam antibiotics: Patients who are allergic to Methicillin or other beta-lactam antibiotics should not be given methicillin due to the risk of severe allergic reactions, such as anaphylaxis.
Liver Disease: Methicillin is metabolized in the liver, so patients with liver disease may require a lower dose of Methicillin. The use of methicillin in patients with severe liver disease should be done with caution.
Renal Impairment: Patients with impaired renal function may require a lower dose of Methicillin or a longer dosing interval. The use of methicillin in patients with severe renal impairment should be done with caution.
Blood Clotting Disorders: methicillin can interfere with blood clotting, so patients with blood clotting disorders or on anticoagulant therapy should be monitored closely for signs of bleeding.
Pregnancy and Breastfeeding: methicillin should be used with caution during pregnancy and breastfeeding. It should only be used if the potential benefits outweigh the risks to the fetus or infant.
Interactions with Other Medications: methicillin can interact with other medications, including anticoagulants, nonsteroidal anti-inflammatory drugs (NSAIDs), and some medications used to treat gout. Patients taking these medications should be monitored closely when receiving methicillin.
Pregnancy consideration:
Pregnancy category: N/A
Breastfeeding warnings: Excreted into the milk is known
Pregnancy category:
Category A: Satisfactory and well-controlled studies show no risk to the fetus in the first or later trimester.
Category B: No evidence of risk to the fetus is found in animal reproduction studies, and there are not enough studies on pregnant women.
Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for a human product; Pregnant women must take care of the potential risks.
Category D: There is adequate data with sufficient evidence of human fetal risk from various platforms. However, despite potential dangers may be used only in emergencies for potential benefits.
Category X: Drugs listed in this category outweigh the risks over benefits. The drug is not for pregnant women.
Pharmacology:
methicillin is a beta-lactam antibiotic that is structurally like penicillin. It works by inhibiting the synthesis of the bacterial cell wall, which leads to the death of susceptible bacteria. Methicillin is resistant to beta-lactamase, an enzyme produced by some bacteria that can break down beta-lactam antibiotics like penicillin.
Pharmacodynamics:
The pharmacodynamics of methicillin involve its ability to inhibit the synthesis of the bacterial cell wall. Methicillin binds to penicillin-binding proteins (PBPs) on the bacterial cell wall, which prevents the formation of peptidoglycan cross-links. This weakens the cell wall and ultimately leads to bacterial cell death.
Pharmacokinetics:
methicillin is administered intravenously and has a short half-life of around 30 minutes. It is primarily eliminated by the kidneys through glomerular filtration and tubular secretion.
Administration:
The administration of methicillin depends on the type and severity of the infection being treated. Methicillin can be given orally, intravenously (IV), or intramuscularly (IM). The dosage and duration of treatment will depend on factors such as the patient’s age, weight, and overall health, as well as the type and severity of the infection.
Patient information leaflet
Generic Name: Â methicillin
Pronunciation: meth-uh-SIL-inÂ
Why do we use methicillin?
methicillin is an antibiotic that is used to treat bacterial infections. Specifically, it is a type of penicillin antibiotic that is effective against certain strains of bacteria that are resistant to other types of penicillin antibiotics.
methicillin is primarily used to treat infections caused by the bacteria Staphylococcus aureus (S. aureus). This includes skin and soft tissue infections, bone infections, and pneumonia. Methicillin may also be used to treat endocarditis, which is an infection of the heart valves.
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