Pharmacology for Technicians PTCB Test Prep

Antibacterial Drugs to Know for the PTCB Exam!

Mar 3rd, 2020
antibacterial drugs

Antimicrobial Drugs

For the PTCB exam syllabus, the “Medications” category now carries a weighting of 40%. As a pharmacy technician, you should have the knowledge and experience to identify the most encountered antibacterial drugs.

Today we review the following five antibacterial drug classes:

  • Penicillins
  • Cephalosporins
  • Tetracyclines
  • Macrolides
  • Fluoroquinolones

Bear in mind that candidates are not required to understand the clinical details of each drug class. Instead, you must be able to identify an antibacterial drug and to have some knowledge of why it’s used in pharmacy.


Penicillins are some of the most widely used antibacterial drugs.

They are also among some of the oldest such drugs. Examples of penicillins commonly dispensed in pharmacies include:

  • Amoxicillin
  • Ampicillin
  • Flucloxacillin
  • Piperacillin

Note: all penicillins can be identified with the suffix -cillin.

As such, all penicillins have the same mechanism of action.

The mechanism of action of a drug refers to how the drug works to achieve its therapeutic effects. In the case of penicillins, they work by interfering with the bacterial cell wall. They weaken the wall, which allows water to enter bacteria and result in bursting (lysis) and the death of bacteria.

Penicillins are used to treat bacterial infections including tonsillitis, pneumonia (in combination with other drugs), skin and soft tissue infections, tetanus, and septicemia. This is not an exhaustive list of conditions.


There are now 5 generations of cephalosporins, with each generation containing its own cephalosporin drugs. For the purposes of the PTCB test, candidates are not required to know all cephalosporins and to which generation they belong.

Cephalosporins are structurally like penicillins. Both drug classes contain what is called a beta-lactam ring. This square-like, 4-membered ring in their chemical structure is what is responsible for their antimicrobial effects. For this reason, drugs such as penicillins and cephalosporins are often collectively referred to as beta-lactam antibacterial drugs.

As a result, they have the same mechanism of action – water entry, bursting and death of bacterial cells.

Cephalosporins are easily identified with their prefix – cefa, ceft, cefra etc.

Examples include:

  • Cefalexin
  • Cefazolin
  • Cefoxitin
  • Ceftazidime
  • Ceftriaxone

Whilst you do not need to memorize the entire list of cephalosporins, you should be able to identify a cephalosporin from a list of drugs and, by extension, know that it is used to treat bacterial infections.


Tetracyclines do not work like penicillins or cephalosporins.

Instead, tetracyclines work as protein synthesis inhibitors. In other words, bacteria produce proteins to ensure that they are correctly regulated. Drugs such as tetracyclines interfere with the synthesis of these proteins, which prevents polypeptide chains from forming.

Ultimately, this stops bacterial growth (bacteriostatic) but does not cause bacterial cell death (bacteriocidal). But by limiting bacterial growth, it means the body can step in and eliminate the remaining infection.

Tetracyclines can be easily identified, too. Here are some examples:

  • Tetracycline
  • Minocycline
  • Doxycycline

Note that tetracyclines always end in the suffix – cycline.

Tetracyclines are used in the treatment of acne, lower respiratory tract infections – including pneumonia, pelvic inflammatory disease, Lyme disease, and malaria.


Macrolides work like tetracyclines, as protein synthesis inhibitors.

However, though they have a similar mechanism of action, the site at which they interfere with protein synthesis is different.

Examples of macrolides include:

  • Erythromycin
  • Clarithromycin
  • Azithromycin

Though all macrolides end in the suffix -mycin, this is not sufficient to identify the drug as a macrolide. That’s because many other antibacterial drugs, which are not macrolides, also have the same suffix.

Nonetheless, by identifying -mycin within a medicine, you will know that it’s an antimicrobial drug. If you can, though, it would be beneficial to commit the above three drugs to memory.

Macrolides are used to treat respiratory infections, skin and soft tissue infections, severe pneumonia, and eradication of Helicobacter pylori infection alongside a penicillin and a proton-pump inhibitor (drugs used to prevent gastric acid production).


Finally, we arrive at the fluoroquinolones; the last of our antibacterial drugs.

Fluoroquinolones do not work as cell wall synthesis inhibitors (like penicillins or cephalosporins), nor do they work by interfering with protein synthesis (like tetracyclines and macrolides).

Instead, fluoroquinolones work as inhibitors of DNA synthesis. By inhibiting DNA synthesis, bacterial cells cannot replicate.

Fluoroquinolones are widely used antibacterial drugs and can be identified with the suffix -oxacin:

  • Moxifloxacin
  • Ciprofloxacin
  • Levofloxacin
  • Norfloxacin

These drugs are very effective against urinary tract infections (UTIs), severe gastrointestinal infections, lower respiratory tract infections (moxifloxacin, levofloxacin), whilst ciprofloxacin is also effective against Pseudomonas aeruginosa infections.

Final Thoughts

That concludes our study of antibacterial drugs.

We have covered the top 5 antibacterial drug classes you need to know for the PTCB exam. Of course, there are many other drug classes but, as the most common, this is the best place to start.

Candidates can expect PTCB questions on these drug classes, most likely questions on the ability to identify an antibacterial drug from a list of medicines, or to identify the active ingredient in some of the most widely used antibiotics.

If you would like to practice PTCB practice tests on antimicrobial drugs, take a few moments to create an account with PTCB Test Prep. In the meantime, check back to our PTCB Test Prep blog soon for more great content to help you pass the pharmacy technician exam!

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PTCB Test Prep Author


Elaine Walker

Elaine joined PTCB Test Prep in 2017, currently serving as the lead product development manager overseeing both course development and quality improvement. Mrs. Walker is a graduate of California State University and has worked as a pharmacy technician for over twenty years – with particular interests in pediatric pharmacy, extemporaneous compounding, and hospital pharmacy. Over the past 8-years, she has helped prepare thousands of students for the PTCB examination.