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Penicillins (Oral)

Drug Class: Commonly Known As: Category:
Penicillins (Oral)

Penicillins (Oral) - Side Effects, Precautions, and Contraindications

What side effects can Penicillins (Oral) cause?

Some common side effects include:

  • Diarrhoea
  • Nausea, vomiting
  • Stomach upset or discomfort

Although uncommon, you may develop a black, "hairy" tongue while taking Penicillin. This effect is harmless and usually goes away after treatment. Maintain good oral hygiene and brush your tongue with a soft toothbrush twice a day. If any of the side effects do not go away or are serious, please see your doctor.

Rare, but serious side effects include:

  • Vaginal itch or discharge, white spots on lips or in mouth
    o This may indicate a yeast infection which may need treatment.
  • Persistent diarrhoea, abdominal or stomach pain/cramp, blood/mucus in your stool
    o This could suggest a severe intestinal condition (pseudomembranous colitis). This condition may occur during the course of this medication or weeks after this medication has stopped. Do not use anti-diarrhoea products or narcotic pain medications if you have the symptoms because these products may make them worse.

The symptoms of a drug allergy include one or more of the following:      

  • Swollen face/eyes/lips/tongue      
  • Difficulty in breathing
  • Itchy skin rashes over your whole body       
  • Sores in the mouth, red painful eyes or blisters on the skin

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

Before taking Penicillins (Oral), what precautions must I follow?

Inform your healthcare professional if:

  • You had a previous allergic reaction to Amoxicillin, Cloxacillin, Cephalexin, Cefuroxime or other beta lactam antibiotics.
  • You are taking any other medications, including supplements, traditional medications and herbal remedies.
  • You have kidney problems.
  • You are pregnant, planning to become pregnant, or breastfeeding.

What food or medicine must I avoid when I take Penicillins (Oral)?

  • Space this medication 2 hours apart from probiotics.
  •  Inform your doctor if you are taking any other medications such as Methotrexate, antibiotics (e.g. Tetracyclines), blood thinners (e.g. Warfarin), Probenecid, and oral contraceptives.

Penicillins (Oral) - Additional Information

  • Updated on Friday, April 30, 2021
  • Article contributed by PSS National Medication Information Workgroup PSS National Medication Information Workgroup

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