Principen - How to use | Interactions

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Principen is a beta-lactam antibiotic and it has bactericidal effect (killing bacteria). It contains active substance called amoxicillin. It is used to treat infections caused by microorganisms susceptible to Principen. Mostly, this medicine is effective against Gram positive bacteria. Some studies have shown that it is also effective against Escherichia coli.1

It is one of the most commonly used antibiotics nowadays in the treatment of the following conditions:

  • Inflammation of the sinuses
  • Inflammation of the ear
  • Urinary tract infections such as: glomerulonephritis, cystitis and others.
  • Gonorrhea. Pilkevich and all shown that Principen is very effective in these patients even if they were previously treated with other antibiotics. Most of patients started feeling improvement after the first day of treatment.2
  • Infant fever. Use of this medicine to treat infant fever is justified even in 1-month old newborns.3
  • Upper respiratory tract infections (tonsillitis, bronchitis and pneumonia).
  • Antibiotic prophylaxis in dental practice.


Although most of experts claim that amoxicillin reduces effectiveness of oral contraceptives, some studies have shown that most woman taking ethyniloestradiol or levonorgestrel (birth control pills) do not need to use alternative contraception method. However, this study has also shown that concentrations of these medicines in the blood were lower in two women (13 woman was studied). So we can conclude that this medicine decrease effectiveness of birth control pills.4

Since Principen can cause asthma and asthmatic status, it should be avoided in these patients.5,6

It also should be avoided in patients allergic to penicillin antibiotics, such as:

  • amoxicillin,
  • penicillin,
  • cefapan,
  • cefdinir,
  • cefixime,
  • cefadroxil,
  • cefopodoxime,
  • cefepime,
  • ceftazidime,
  • ceftibuten and others.

There is an increased incidence of skin rash in patients with leukemia taking Principen.

People often believe that this medicine will help them in the treatment of colds and flu (viral infections). However, Principen is not effective against viral infections.

Take this medicine only under medical supervision.

Use of Principen during pregnancy and breastfeeding

One teratologic study has shown that active ingredient of Principen (ampicillin) may cause only cleft palate but warns that further research are necessary. Talk to your doctor before you start using Principen during breastfeeding.7

Small amounts of this medicine passes into breast milk. Avoid breastfeeding while taking this medicine.

How to use

To see recommended dosage regimens, check this article: Ampicillin

Use with other medicines (Interactions)

Principen should be avoided in combination with following medicines:

  • Medicine used to treat malaria: Quinine. This medicine may decrease effectiveness of Principen.8
  • Atenolol (medicine used to treat heart diseases). Concomitant use of Principen with this medicine, may cause decrease in concentration of Atenolol in the blood which reduce its effectiveness. This interaction is possible only if high doses of Principen are prescribed.9
  • Levonorgestrel and other oral contraceptives.
  • Chloramphenicol.
  • Ciprofloxacin.
  • Gentamicin
  • Garlic extract

Before you start taking this medicine, you should tell your doctor about all medicines you are taking.

Side effects

To see what are the possible side effects of this medicine, visit: Ampicillin.


  1. I.P.Thonus, P Fontijne and MF Michael. Ampicillin susceptibility and ampicillin-induced killing rate of Escherichia coli.  Antimicrob Agents Chemother. 1982: 22 (3): 386-390.
  2. Pilkevich RN, Gulitskaia NI, Iagovdik NZ and others. Ampicillin treatment trial in gonorrhea recurrences. Antibiotiki. 1979: 24 (10): 777-9.
  3. Brown JC, Burns JL, Cummings P. Ampicillin use in infant fever: a systematic review. Arch Pediatr Adolesc Med. 2002: 156 (1): 27 - 32.
  4.  DJ Back, AM Breckenridge, M Maclver, and others. The effects of ampicillin oral contraceptive steroids in women. Br J Clin Pharmacol.1982: 14 (1): 43-48.
  5. Wuthrich B, Hartmann Al. Occupation-related bronchial asthma caused by ampicillin. Diagnostic significance of occupation-specific inhalation provocation tests. Scheweiz Med Wochenschr. 1982: 112 (29): 1046-8.
  6. Gomez Orosco L. Asthmatic status caused by ampicillin. Alergia. 1976: 23 (1): 23-8.
  7. Czeizel AE, Rockenbauer M, Sorensen HT and others. A population-based case-control teratologic study of ampicillin treatment during pregnancy. Am J Obstet Gynecol. 2001: 185 (1: 140-7.)
  8. Falad OB, Falusi AG, Olaniyi AA and others. Significant Pharmacokinetic Interactions Between  Quinine and Ampicillin-Cloxacillin Combination. Drugs RD. 2016: 16 (2): 193-203.
  9. AJ McLean, A. Tonkin, P. McCarthy and others. Dose-dependence of atenolol-ampicillin interaction. Br J Clin Pharmacol. 1984: 18 (6): 969-971.

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