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Principen Prescribing Information

Principen is the brand name for a medication called ampicillin. Ampicillin is an antibiotic that belongs to the penicillin group of antibiotics. It is used to treat a variety of bacterial infections, including respiratory tract infections, urinary tract infections, skin and soft tissue infections, and certain types of gastrointestinal infections.

Ampicillin works by interfering with the formation of the bacterial cell wall, which ultimately leads to the death of the bacteria.

Principen capsules

Uses of Principen

Principen, also known by its generic name ampicillin, is an antibiotic medication. It is primarily used to treat bacterial infections caused by susceptible strains of bacteria. Here are some common uses:

  • Respiratory Tract Infections: Antibiotic can be used to treat infections of the respiratory system, such as bronchitis and pneumonia caused by susceptible bacteria.
  • Urinary Tract Infections (UTIs): It is effective against certain types of bacteria that cause urinary tract infections.
  • Skin and Soft Tissue Infections: Principen can be used to treat infections of the skin, as well as soft tissue infections like cellulitis.
  • Gastrointestinal Infections: It can be used to treat infections of the gastrointestinal tract, including those caused by bacteria like E. coli.
  • Ear, Nose, and Throat Infections: Medicine may be prescribed for infections of the ear, nose, and throat, such as otitis media (ear infection) and sinusitis.
  • Gynecological Infections: It can be used for certain infections of the female reproductive system, such as bacterial vaginosis.
  • Meningitis: In some cases, Principen may be used in the treatment of bacterial meningitis, particularly if the causative organism is susceptible to ampicillin.
  • Endocarditis: In combination with other antibiotics, it may be used to treat bacterial endocarditis, an infection of the lining of the heart chambers and valves.
  • Prophylaxis for Surgical Procedures: In some cases, Principen may be given before certain surgeries to prevent post-operative infections.

It's important to note that Principen is only effective against bacterial infections and will not work against viral infections like the common cold or flu.


The dosage of Principen can vary depending on the type and severity of the infection, as well as other individual factors such as your age, weight, and overall health. It's crucial to follow the dosing information on the prescription label. Here are some general guidelines for the typical dosages:

Adults and Adolescents (13 years and older):

  • For mild to moderate infections: 250 mg to 500 mg every 6 hours.
  • For more severe infections: 1 gram to 2 grams every 4 to 6 hours.

Children (under 13 years):

The dosage for children is usually based on their weight.

  • Infants: Infants typically receive lower dosages based on their weight and the severity of the infection.
  • Neonates: Neonates (newborns) may receive a different dosage, which is determined by their age and weight.

Remember to complete the full course of treatment, even if your symptoms improve before you finish the prescribed medication. Stopping antibiotics prematurely can lead to the survival of bacteria and a risk of recurrence or antibiotic resistance.

Additionally, if you miss a dose, take it as soon as you remember. If it's close to the time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double up on doses to make up for a missed one.

Side Effects of Principen

Principen is an antibiotic medication that can be effective in treating bacterial infections. However, like all medications, it can potentially cause side effects. Not everyone will experience these side effects, and some people may experience them to varying degrees of severity. Common side effects may include:

Gastrointestinal Distress: Ampicillin can often cause gastrointestinal side effects, including:

  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal pain or discomfort

Allergic Reactions: In some cases, individuals may be allergic to ampicillin, which can lead to more severe reactions, such as:

  • Skin rash or hives
  • Itching
  • Swelling of the face, lips, or tongue
  • Difficulty breathing or wheezing
  • Severe diarrhea (potentially indicating a severe intestinal condition known as pseudomembranous colitis, which can be caused by Clostridium difficile bacteria)

Superinfections: Ampicillin can disrupt the balance of normal bacteria in the body, which can lead to the overgrowth of other organisms. This may result in secondary infections, such as oral thrush or vaginal yeast infections.

Hypersensitivity Reactions: Some individuals may experience a hypersensitivity reaction that can cause symptoms such as fever, joint pain, and enlarged lymph nodes.

Blood Disorders: Rarely, ampicillin can affect blood cell counts, leading to conditions like leukopenia (a decrease in white blood cells) or thrombocytopenia (a decrease in platelets).

Kidney Problems: In rare cases, ampicillin may lead to kidney problems, including interstitial nephritis.

Liver Issues: Elevated liver enzymes have been reported in some cases.

Neurological Symptoms: High doses of ampicillin can rarely lead to neurologic symptoms such as confusion, agitation, and seizures.

It's essential to note that severe allergic reactions to ampicillin can be life-threatening and require immediate medical attention. If you experience symptoms of an allergic reaction, such as difficulty breathing or swelling of the face, seek emergency medical care.

Interaction with other drugs

Principen can interact with other drugs, and these interactions may affect the effectiveness and safety of both Principen and the other medications involved. Here are some potential drug interactions:

  • Oral Contraceptives: Ampicillin may reduce the effectiveness of oral contraceptive pills. It is recommended to use an additional form of contraception, such as condoms, while taking ampicillin.
  • Anticoagulants (Blood Thinners): Ampicillin can increase the effects of blood-thinning medications like warfarin, potentially leading to an increased risk of bleeding. Monitoring and adjustment of the anticoagulant dose may be necessary.
  • Allopurinol: The combination of ampicillin and allopurinol can increase the risk of developing a skin rash.
  • Probenecid: Probenecid can delay the excretion of ampicillin from the body, leading to higher ampicillin levels in the bloodstream. This interaction may be utilized in certain situations to enhance the effectiveness of ampicillin.
  • Methotrexate: Ampicillin can increase the levels of methotrexate in the blood, potentially leading to methotrexate toxicity. Adjustments in methotrexate dosing and careful monitoring may be necessary if these drugs are used together.
  • Aminoglycoside Antibiotics: When used together with aminoglycoside antibiotics like gentamicin or tobramycin, ampicillin can enhance the antibacterial effects against certain infections.
  • Tetracycline Antibiotics: The effectiveness of both ampicillin and tetracycline antibiotics may be reduced when taken together. It's generally recommended to avoid concurrent use unless there are specific clinical reasons to use both antibiotics.
  • Proton Pump Inhibitors (PPIs): Some studies have suggested that PPIs like omeprazole may reduce the absorption of ampicillin. It's advisable to take ampicillin at least 2 hours before or after taking a PPI.
  • Methoxyflurane: Concurrent use of ampicillin and methoxyflurane may result in kidney damage. These drugs should not be used together.

What to avoid while on Principen

Here are some things to avoid or be cautious about while on Principen:

  • Alcohol: While there is no direct interaction between ampicillin and alcohol, it's generally advisable to limit or avoid alcohol consumption when you have an infection. Alcohol can weaken the immune system and potentially interfere with your body's ability to fight the infection. Moreover, alcohol may cause gastrointestinal irritation, which can compound any stomach upset caused by ampicillin.
  • Grapefruit and Grapefruit Juice: Some medications can interact with compounds found in grapefruit and grapefruit juice, affecting how they are metabolized in the body.
  • Antacids and Calcium Supplements: Avoid taking antacids or calcium supplements within two hours of taking ampicillin. These products can interfere with the absorption of ampicillin, making it less effective.
  • Birth Control Pills: Ampicillin can reduce the effectiveness of birth control pills (oral contraceptives). To prevent unwanted pregnancies, use an additional form of contraception, such as condoms, while taking ampicillin and for at least one week after finishing the course of antibiotics.
  • Certain Dairy Products: Calcium-rich dairy products, such as milk, cheese, and yogurt, may reduce the absorption of ampicillin. To maximize the effectiveness of the medication, it's best to take it on an empty stomach, about 1 hour before or 2 hours after meals.
  • Driving and Operating Machinery: Ampicillin is not known to cause significant drowsiness or impairment of motor skills. However, if you experience any unusual side effects, such as dizziness or confusion, while taking the medication, it's best to avoid activities that require alertness until you feel normal again.
  • Discontinuing Treatment Prematurely: Stopping antibiotics too soon can lead to the survival of bacteria and the potential for recurrence or antibiotic resistance.

Contraindications of Principen

Contraindications are conditions or situations in which a medication like Principen should not be used due to the potential for harm or adverse effects. Here are some contraindications and situations in which the use should be avoided:

  • Allergy to Penicillins or Beta-Lactam Antibiotics: If you have a known allergy to ampicillin, other penicillin antibiotics, or beta-lactam antibiotics, you should not take Principen. Allergic reactions to these medications can range from mild skin rashes to severe, life-threatening reactions.
  • Mononucleosis (Mono): Antibiotic is generally not recommended for the treatment of infections in individuals with mononucleosis. It can cause a skin rash known as a maculopapular rash in people with mono, which is not necessarily an allergic reaction but is more common in this population.
  • Severe Kidney Dysfunction: Ampicillin is primarily excreted through the kidneys, and reduced kidney function can lead to the accumulation of the drug in the body, potentially causing toxicity.
  • Certain Gastrointestinal Conditions: Principen should be used with caution in individuals with a history of gastrointestinal diseases, especially colitis. It can disrupt the balance of normal gut flora and potentially lead to the development of pseudomembranous colitis caused by Clostridium difficile bacteria.
  • Severe Liver Dysfunction: While ampicillin does not primarily affect the liver, severe liver dysfunction may require dose adjustments or alternative treatments.
  • Seizure Disorders: Ampicillin can occasionally lower the seizure threshold, which may be a concern for individuals with a history of seizure disorders.
  • Certain Hematologic Disorders: Drug can affect blood cell counts, so it should be used with caution in individuals with certain hematologic disorders, such as leukopenia (a decrease in white blood cells) or thrombocytopenia (a decrease in platelets).

Pregnancy and Principen

The use of Principen during pregnancy should be carefully considered. Here's some information about using this drug during pregnancy:

  • Safety Profile: Ampicillin is generally considered safe for use during pregnancy when the potential benefits outweigh the potential risks. It falls into Category B of the U.S. Food and Drug Administration's (FDA) pregnancy categories, which means that animal studies have not shown harm to the fetus, but there are limited human studies available. While there is no conclusive evidence of harm to human fetuses, the medication should be used during pregnancy only when clearly needed.
  • Infections During Pregnancy: In some cases, bacterial infections that occur during pregnancy may pose a greater risk to the health of both the mother and the developing fetus than the use of antibiotics like Principen. Untreated infections can potentially lead to complications.
  • Bacterial Infections: Principen may be prescribed during pregnancy to treat bacterial infections such as urinary tract infections, respiratory infections, or skin infections.
  • Dosage and Monitoring: The goal is to effectively treat the infection while minimizing potential risks to the developing fetus.
  • Allergic Reactions: Some individuals may be allergic to ampicillin, and allergic reactions can occur during pregnancy. Allergic reactions can be serious.
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