PTCB Guide to Tetracyclines!Jun 10th, 2023
PTCB Guide to Tetracyclines
Antibacterial drugs are among the most widely dispensed medicines.
Pharmacy technicians can expect to at least encounter some PTCB exam questions on this subject. It’s also a big subject, with many different antibacterial drug classes, mechanisms, side effects, and drug interactions.
Of course, technicians are not expected to have an in-depth knowledge of each drug class. Instead, you are expected to know the major details only. Here, we break those major details down – in the context of tetracyclines. Later in this PTCB guide to tetracyclines, we review major side effects and drug interactions.
What are Tetracyclines?
Tetracyclines are a widely used antibacterial drug class.
They are used in the treatment of many bacterial infections; and are therefore classified as having a broad-spectrum of activity. Among these infections include:
- Acne vulgaris.
- Lower respiratory tract infections (LRTIs).
- Chlamydial infection, including pelvic inflammatory disease.
- Other infections including typhoid, malaria, and Lyme disease.
Pharmacy technicians are sure to regularly dispense tetracyclines to patients, given that over 25 million prescriptions for these drugs are made each year.
Examples of tetracyclines and their common brands include:
How do tetracyclines work?
Common PTCB test questions ask about mechanisms of action – in other words, how the drug class works.
Tetracyclines work as protein synthesis inhibitors.
By inhibiting the production of new proteins inside bacterial cells, tetracyclines disrupt many of the fundamental processes that keep that bacterial cell alive – and so the bacteria are killed.
By slowing the rate of bacterial reproduction, it gives the immune system an opportunity to step in to battle and remove the bacteria from the body.
That said, many bacteria have developed the means to defend themselves against tetracyclines. Bacterial resistance to these drugs continues to rise. This makes tetracyclines less effective than when they were first introduced, but they still have significant clinical activity that warrants their continued use in medicine.
Tetracyclines are generally well-tolerated medicines.
Possible side effects include:
- Nausea and vomiting
- Hypersensitivity reactions, such as skin rash
- Esophageal irritation and ulceration
- Photosensitivity – an increased risk of sunburn
Tetracyclines can also cause tooth discoloration and tooth enamel hypoplasia (thin or absent enamel).
Tetracyclines are contraindicated in pregnancy (and children younger than 12-years) due to the risk of tetracyclines binding to teeth and bones.
Taking expired tetracyclines can cause Fanconi syndrome – a defect in the kidneys that causes poor absorption of electrolytes such as sodium and potassium.
Tetracyclines bind to multivalent ions, including:
- Magnesium ions
- Aluminum ions
- Zinc ions
- Calcium ions
- Iron ions
Therefore, taking foods or medicines – including antacids and dairy products – that contain any of these ions can disrupt the absorption of tetracyclines. These foods and medicines should be avoided within 2-hours of taking tetracycline antibacterial drugs.
Tetracyclines can also enhance the anticoagulant effects of warfarin. That’s because gut bacteria produce vitamin K, and this vitamin opposes the effects of warfarin. Tetracyclines kill gut bacteria, reducing vitamin K production – and so this increases the anticoagulant effects of warfarin.
Pharmacy technicians are expected to know the major facts about tetracyclines. Here, we have attempted to put together the must-know facts that always get tested.
In review, we have learned:
- Tetracyclines are an antibacterial drug class used to treat a broad-range of infections – from acne to pneumonia to malaria.
- Widely dispensed examples include doxycycline, minocycline, tetracycline, and demeclocycline.
- Tetracyclines work as protein synthesis inhibitors.
- Bacterial resistance continues to rise, but tetracyclines remain an effective antimicrobial drug class.
- They are well-tolerated drugs, but they can cause photosensitivity, tooth discoloration and enamel hypoplasia.
- Foods or medicines that contain multivalent ions – such as calcium or magnesium – can impair tetracycline absorption. This includes dairy products and antacids.
- Tetracyclines can enhance the anticoagulant effects of warfarin (increasing the risk of bleeding).
- Tetracyclines are avoided in pregnancy and children younger than 12-years due to the drug binding to teeth and bones.
Check back to our PTCB blog soon for even more rapid reviews of the drug classes and medicines you need to know. Tetracyclines are almost always tested in some capacity on the pharmacy technician exam and committing these facts to memory is sure to have you covered for this topic.
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