> Western Medicines > Ampicillin


Used for: Bacterial meningitis, Urinary tract infections (UTIs), Susceptible infections, Gonorrhea, Sepsis, Endocarditis
Chinese name:

What is Ampicillin for?

Ampicillin belongs to a class of medications called penicillins. It kills bacteria by interrupting the integrity of bacterial cell walls. Ampicillin is used to treat various infections, including bacterial meningitis, urinary tract infections and systemic infections. Ampicillin does not work for virus or fungus infections.

How to use it?

Ampicillin is available as capsules and syrup, which are taken by mouth. Oral Ampicillin should be taken on an empty stomach (1 hour before or 2 hours after meal).


Susceptible infections (including bronchitis, urinary tract infections, otitis media, sinusitis, uncomplicated community-acquired pneumonia, salmonellosis)
Oral: 0.5-1 g every 4-6 hours.
Injections/infusions: 500 mg every 4-6 hours.

Child 12-17 years
Oral: 500 mg 4 times daily, increase if necessary to 1 g 4 times daily.

Child 5-11 years
Oral: 500 mg 4 times daily, increase if necessary up to 30 mg/kg body weight 4 times daily. Maximum 1 g per dose.

Child 1-4 years
Oral: 250 mg 4 times daily, increase if necessary up to 30 mg/kg body weight 4 times daily.

Child 1-11 months
Oral: 125 mg 4 times daily, increase if necessary up to 30 mg/kg body weight 4 times daily.


Urinary tract infections
Oral: 500 mg every 8 hours.

What are the side effects of Ampicillin?

Common side effects of Ampicillin include diarrhoea, nausea and vomiting, and allergic skin reactions.

Who should not take Ampicillin?

  • Anyone who has an allergy to Ampicillin or other penicillins.

Pharmacist Tips:

  • Antibiotics like Ampicillin may reduce the effectiveness of oral contraceptives. Consider using another form of contraception while taking Ampicillin.
  • You must complete the entire course of this antibiotic, or else, the infection will not be properly controlled.

Common dosing schedule:
Take Ampicillin on an empty stomach (1 hour before or 2 hours after meals) which enhances its absorption.


This schedule is for reference only, adjustments may be made according to individual needs.


Some common medications Ampicillin may interact with:

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Ampicillin in Hong Kong?

In Hong Kong, Ampicillin is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.


For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at https://www.drugoffice.gov.hk

Need more information?

For detailed information about the use of Ampicillin in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.

Brands in Hong Kong
Available dosage
  • 250mg / 500mg (Capsules)
  • 250mg/5ml (Syrup)
  • 500mg / 750mg / 1.5g (Injections)
Drug class
Sub class
Other drugs in same class
Used for: Dental infections, Other bacterial infections, Urinary tract infections (UTIs), Ear infections, Helicobacter pylori (H. pylori) eradication, Respiratory tract infections
Chinese name:
Used for: Susceptible bacterial infections
Chinese name:
Amoxicillin+Clavulanic acid
Used for: Urinary tract infections (UTIs), Other bacterial infections, Ear infections, Respiratory tract infections, Helicobacter pylori (H. pylori) eradication, Dental infections
Used for: Urinary tract infections (UTIs), Intra-abdominal infections, Gonorrhea, Skin and soft tissue infections, Respiratory tract infections, Bone and joint infections
Chinese name:
Used for: Gonorrhea, Bacterial infections, Prevention of surgical infections
Chinese name:
Used for: Skin and soft tissue infections, Intra-abdominal infections, Appendicitis, Urinary tract infections (UTIs), Pneumonia