Ampicillin – Dose, ROA, MOA, PK, PD, Indications & More

Dose and Dosage: The dosage of Ampicillin varies depending on the type and severity of the infection, as well as the patient’s age, weight, and renal function. For adults, the typical dosage for most infections is 250 to 500 mg orally every 6 hours or 1 to 2 grams intravenously (IV) every 4 to 6 hours. The dosage for pediatric patients is typically calculated based on body weight and administered orally or intravenously every 6 hours.

Frequency: The frequency of Ampicillin administration depends on the type and severity of the infection being treated. In general, it is administered every 6 hours orally or intravenously. The frequency may be adjusted by a healthcare professional based on the patient’s response to treatment and the presence of any adverse effects.

Route of Administration (ROA): Ampicillin is administered orally as capsules or suspension, or intravenously as a solution for injection. The route of administration may vary depending on the patient’s condition, the type of infection, and the severity of symptoms.

Mechanism of Action (MOA): Ampicillin is a broad-spectrum penicillin antibiotic that works by inhibiting the synthesis of bacterial cell walls. It achieves this by interfering with the transpeptidation reaction, which is essential for cross-linking of peptidoglycan chains in bacterial cell walls. This leads to bacterial cell lysis and death.

Pharmacokinetics (PK): After oral administration, Ampicillin is rapidly absorbed from the gastrointestinal tract and reaches peak plasma concentrations within 1 to 2 hours. It is widely distributed throughout the body and penetrates into various tissues and fluids, including the cerebrospinal fluid (CSF) in the presence of inflammation. Ampicillin is primarily excreted unchanged in the urine via renal filtration and tubular secretion.

Pharmacodynamics (PD): The pharmacodynamic effects of Ampicillin include its bactericidal activity against a wide range of gram-positive and gram-negative bacteria. It acts by disrupting bacterial cell wall synthesis, leading to cell lysis and death. The time-dependent killing activity of Ampicillin is enhanced by maintaining plasma concentrations above the minimum inhibitory concentration (MIC) for the target bacteria.

Pathophysiology: Ampicillin is indicated for the treatment of various bacterial infections caused by susceptible organisms, including respiratory tract infections, urinary tract infections, skin and soft tissue infections, gastrointestinal infections, and certain sexually transmitted infections.

Indications: Ampicillin is indicated for the treatment of bacterial infections caused by susceptible organisms. It is commonly used to treat respiratory tract infections, urinary tract infections, skin and soft tissue infections, gastrointestinal infections, and certain sexually transmitted infections.

Contraindications: Ampicillin is contraindicated in patients with a known allergy to penicillin antibiotics or any of the components of the medication. It should also be used with caution in patients with a history of allergic reactions to cephalosporin antibiotics or other beta-lactam antibiotics.

Drug Interactions: Ampicillin may interact with certain medications, including oral contraceptives, probenecid, allopurinol, and aminoglycoside antibiotics. Concurrent use of Ampicillin with these medications may alter their pharmacokinetics or efficacy. It is essential to inform your healthcare provider about all medications you are taking, including over-the-counter and herbal supplements, to avoid potential interactions.

Monitoring and Laboratory Tests: Before initiating treatment with Ampicillin, healthcare providers may perform baseline assessments, including physical examination, laboratory tests (such as complete blood count and renal function tests), and microbial cultures as needed. During treatment, regular monitoring of clinical symptoms, laboratory parameters, and treatment response is essential to assess efficacy and detect any potential adverse effects or complications.

Always consult with a healthcare professional for personalized medical advice and recommendations regarding the use of Ampicillin or any other medications.


Why is this medication prescribed?
Ampicillin is prescribed to treat a wide variety of bacterial infections caused by susceptible organisms. It is commonly used to treat respiratory tract infections, urinary tract infections, skin and soft tissue infections, gastrointestinal infections, and certain sexually transmitted infections.

How should this medicine be used?
Ampicillin is typically taken orally as capsules or suspension, or administered intravenously as a solution for injection. The dosage and duration of treatment depend on the type and severity of the infection, as well as the patient’s age, weight, and renal function. It is essential to follow the dosing instructions provided by your healthcare provider.

Other uses for this medicine
In addition to its primary use in treating bacterial infections, Ampicillin may also be used off-label for certain other conditions, as determined by a healthcare provider. However, such usage should be under the guidance of a healthcare professional.

What special precautions should I follow?
Before taking Ampicillin, inform your healthcare provider about any allergies you have, especially to penicillin antibiotics or any of the components of the medication. Also, let your doctor know about any medical conditions you have, particularly kidney disease or a history of gastrointestinal problems. Ampicillin should be used with caution in patients with a history of allergic reactions to cephalosporin antibiotics or other beta-lactam antibiotics.

What special dietary instructions should I follow?
There are no specific dietary restrictions associated with Ampicillin use. However, it’s essential to maintain a balanced diet and stay hydrated while taking the medication to support your overall health and aid in the treatment of the bacterial infection.

What should I do if I forget a dose?
If you miss a dose of Ampicillin, take it as soon as you remember, unless it’s almost time for your next dose. In that case, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to make up for the missed one.

What side effects can this medication cause?
Common side effects of Ampicillin may include nausea, vomiting, diarrhea, abdominal pain, rash, itching, and allergic reactions such as hives or difficulty breathing. More severe side effects may include severe diarrhea, fungal infections, or anaphylaxis. Contact your healthcare provider if you experience any unusual or severe side effects while taking Ampicillin.

What should I know about storage and disposal of this medication?
Store Ampicillin capsules or suspension at room temperature away from moisture and heat. Keep the medication out of reach of children and pets. Ampicillin solutions for injection should be stored according to the manufacturer’s instructions and disposed of properly after use. Do not use Ampicillin if it has expired or if the capsules or suspension have changed color or have particles in them.

In case of emergency/overdose
If you suspect an overdose of Ampicillin or experience symptoms such as severe nausea, vomiting, or diarrhea, seek immediate medical attention or contact a poison control center right away.

Always follow the instructions of your healthcare provider and pharmacist regarding the use, storage, and disposal of Ampicillin. If you have any questions or concerns about Ampicillin or its use, don’t hesitate to discuss them with your healthcare provider.