Usage
Ampicillin + Dicloxacillin is a combination antibiotic medication primarily prescribed for bacterial infections. It falls under the pharmacological classification of beta-lactam antibiotics, specifically penicillins. This combination is effective against a broad spectrum of bacteria. It works by inhibiting bacterial cell wall synthesis, ultimately leading to bacterial cell death. It is particularly useful against penicillinase-producing staphylococci, thanks to the inclusion of dicloxacillin.
Alternate Names
While there isn’t a widely recognized international non-proprietary name (INN) for this specific combination, it is sometimes referred to simply as “Ampicillin/Dicloxacillin.” Brand names vary depending on the region and manufacturer. Some examples include Ampiclox, StayHappi Ampicillin + Dicloxacillin, amongst others.
How It Works
Pharmacodynamics: Ampicillin + Dicloxacillin exerts its bactericidal effect by disrupting the synthesis of peptidoglycans, essential components of bacterial cell walls. Both components bind to penicillin-binding proteins (PBPs) within the bacterial cell wall, inhibiting the transpeptidation and cross-linking reactions necessary for cell wall stability. This weakens the cell wall, causing bacterial lysis and death. Dicloxacillin’s presence extends the effectiveness to penicillinase-producing bacteria, which would otherwise inactivate ampicillin.
Pharmacokinetics: Ampicillin is well-absorbed orally, while dicloxacillin’s oral absorption is somewhat less reliable but improved when taken on an empty stomach. Both drugs are distributed widely throughout the body, achieving therapeutic concentrations in various tissues and fluids. Metabolism is minimal for both drugs. Elimination primarily occurs via renal excretion, requiring dose adjustments in patients with renal impairment.
Dosage
Standard Dosage
Adults:
The typical adult dose is 250 mg to 500 mg every six hours, administered orally. The dose and duration of therapy depend on the infection’s severity and the patient’s response.
Children:
Pediatric dosing is weight-based, typically ranging from 12.5 mg/kg to 25 mg/kg every six hours, administered orally. For children weighing 40 kg or more, the adult dose may be appropriate. Safety and efficacy in infants younger than one month have not been established.
Special Cases:
- Elderly Patients: Dosage adjustments may be necessary based on renal function.
- Patients with Renal Impairment: Dose reduction and/or increased dosing intervals are required.
- Patients with Hepatic Dysfunction: Caution is advised, and dose adjustment may be needed.
- Patients with Comorbid Conditions: Consider comorbid conditions like diabetes (may cause false-positive urine glucose tests) and gastrointestinal disease.
Clinical Use Cases
Dosage in specific clinical settings should be guided by culture and susceptibility testing, clinical response, and local guidelines. The standard dosage recommendations mentioned above usually suffice. Adjustments may be necessary in severe infections.
Dosage Adjustments
- Renal Impairment: Refer to specific renal dosing guidelines based on creatinine clearance.
- Hepatic Dysfunction: No specific dose adjustments are universally established, but caution is advised.
Side Effects
Common Side Effects:
- Diarrhea
- Nausea
- Vomiting
- Rash
- Urticaria
- Abdominal pain or discomfort
- Headache
Rare but Serious Side Effects:
- Allergic reactions (anaphylaxis)
- Pseudomembranous colitis
- Clostridium difficile-associated diarrhea
- Neutropenia
- Hepatic dysfunction
- Interstitial nephritis
- Seizures
Long-Term Effects:
Prolonged use can increase the risk of antibiotic resistance and secondary infections like C. difficile infection.
Contraindications
- Known hypersensitivity to penicillins or cephalosporins
- History of severe penicillin-induced reactions (anaphylaxis, Stevens-Johnson syndrome)
Drug Interactions
- Antibiotics: Tetracyclines may antagonize bactericidal effects. Aminoglycosides may have interactions
- Anticoagulants: May enhance the effect of warfarin.
- Uricosuric Agents: Probenecid may increase and prolong serum levels.
- Methotrexate: Ampicillin may increase methotrexate toxicity.
- Allopurinol: Concurrent use may increase the risk of skin rash.
- Food: Dicloxacillin absorption is reduced with food.
- Alcohol: While not strictly contraindicated, caution is advised.
Pregnancy and Breastfeeding
Ampicillin is classified as Pregnancy Category B by the FDA (animal studies have not shown fetal harm, but controlled human studies are lacking). Dicloxacillin’s safety during pregnancy hasn’t been definitively established. While both drugs are excreted in breast milk, they are generally considered compatible with breastfeeding in low doses. It’s crucial to weigh the potential benefits against the risks and discuss with the patient.
Drug Profile Summary
- Mechanism of Action: Inhibits bacterial cell wall synthesis.
- Side Effects: Diarrhea, nausea, rash, allergic reactions (rarely severe).
- Contraindications: Penicillin/cephalosporin hypersensitivity.
- Drug Interactions: Tetracyclines, warfarin, probenecid.
- Pregnancy & Breastfeeding: Generally considered safe but caution advised. Discuss with the patient.
- Dosage: Adults: 250-500 mg q6h orally. Pediatrics: Weight-based dosing.
- Monitoring Parameters: Renal and liver function, signs of superinfection (especially with prolonged use), complete blood count with differential.
Popular Combinations
There are no formally established “popular combinations” where other drugs are intentionally added to Ampicillin + Dicloxacillin. However, probiotics might be considered to mitigate antibiotic-associated diarrhea.
Precautions
- General Precautions: Assess for penicillin allergy, renal/hepatic function.
- Specific Populations: Refer to the sections on dosage adjustments and pregnancy/breastfeeding.
- Lifestyle Considerations: Moderate alcohol consumption is generally permissible; however, it is always best to check for patient specific advice. Driving restrictions are not typically necessary unless the patient experiences dizziness.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Ampicillin + Dicloxacillin?
A: Adults: 250-500 mg orally every six hours. Children: Weight-based dosing (12.5-25 mg/kg orally every six hours). Adjustments necessary for renal impairment.
Q2: What infections is Ampicillin + Dicloxacillin effective against?
A: It’s effective against a wide range of bacterial infections, including skin and soft tissue infections, respiratory tract infections, urinary tract infections, and infections caused by penicillinase-producing staphylococci.
Q3: What are the most common side effects?
A: Diarrhea, nausea, vomiting, rash, and abdominal discomfort are the most common.
Q4: Can a patient with a penicillin allergy take this medication?
A: No. Patients with a known penicillin allergy should not take this medication. Cross-reactivity with cephalosporins is also possible.
Q5: How should the dosage be adjusted for patients with kidney problems?
A: The dosage needs to be reduced and/or the dosing interval prolonged. Consult renal dosing guidelines based on creatinine clearance.
Q6: Is it safe to take this medication during pregnancy or while breastfeeding?
A: While generally considered safe, consult drug information resources and individual patient risk factors. Discuss with the patient and weigh benefits against potential risks.
Q7: What should I do if a patient experiences an allergic reaction?
A: Discontinue the medication immediately and provide appropriate medical care, including antihistamines, corticosteroids, and epinephrine, as needed.
Q8: Can this medication be taken with food?
A: Ampicillin can be taken with or without food, but dicloxacillin’s absorption is reduced with food. It’s best to take dicloxacillin on an empty stomach, one hour before or two hours after meals.
Q9: Can Ampicillin + Dicloxacillin be used to treat viral infections?
A: No. This medication is only effective against bacterial infections.
Q10: How long should the treatment course typically last?
A: The duration of treatment depends on the type and severity of the infection and typically ranges from 7 to 21 days. It is important to complete the full course prescribed, even if symptoms improve earlier.
