doxycycline

Actions and Spectrum: 

doxycycline is a broad-spectrum antibiotic that belongs to the tetracycline class of antibiotics. It is used to treat a variety of bacterial infections, including respiratory tract infections, urinary tract infections, skin infections, and sexually transmitted infections. Here are some of the actions and spectrum of doxycycline: 

• Bacteriostatic action: doxycycline works by inhibiting the growth and reproduction of bacteria. It does this by binding to the bacterial ribosome, which is responsible for the production of proteins that the bacteria need to survive. 
• Broad-spectrum activity: doxycycline is effective against a wide range of bacteria, including gram-positive and gram-negative bacteria, as well as atypical bacteria and some protozoa. 
• Antimicrobial activity: doxycycline has antimicrobial activity against a variety of microorganisms, including Mycoplasma, Chlamydia, Rickettsia, and spirochetes. 
• Anti-inflammatory properties: doxycycline has anti-inflammatory properties that make it useful in the treatment of conditions such as acne and rosacea. 
• Long half-life: doxycycline has a long half-life, which means that it can be given once or twice daily, making it more convenient for patients. 

DRUG INTERACTION

Contraindicated  

Serious Use Alternative  

Monitor Closely  

Minor  

Frequency not defined:  

Esophageal ulcer 

Increased liver enzymes 

Visual disturbance 

Dysphagia 

Glossitis 

Nausea 

Vomiting 

Diarrhea 

Hepatotoxicity 

Reversible and more frequent photosensitivity reaction 

Dose-related diabetes insipidus  

Discoloration of teeth 

Superinfection, monilial 

None

Contraindication/Caution: 

doxycycline has several contraindications and cautions, including: 

• Hypersensitivity: doxycycline should not be used in patients with a known hypersensitivity to tetracyclines or any of the ingredients in the formulation. 
• Pregnancy and breastfeeding: doxycycline is contraindicated in pregnancy, particularly during the second and third trimesters, as it may harm the fetus or cause permanent discoloration of the teeth in the newborn. It should also be avoided during breastfeeding, as it can pass into breast milk and harm the nursing infant. 
• Children under 8 years of age: doxycycline can cause permanent discoloration of teeth and affect bone growth in children under 8 years of age. 
• Liver and kidney disease: Patients with liver or kidney disease may require a lower dose of doxycycline, as the drug is eliminated from the body through these organs. 
• Photosensitivity: doxycycline can increase the risk of sunburn and photosensitivity, and patients should avoid exposure to sunlight or tanning beds while taking the medication. 
• Drug interactions: doxycycline can interact with other medications, including antacids, iron supplements, and certain antibiotics, and may reduce their effectiveness or increase the risk of side effects. 
• Intracranial hypertension: doxycycline can cause an increase in intracranial pressure, particularly in women of childbearing age, which can lead to vision changes, headaches, and other neurological symptoms. 

Pregnancy considerations: doxycycline can be assigned under pregnancy category D. Avoid during pregnancy. 

Lactation: Doxycycline can be excreted in breast milk and may cause tooth discoloration in infants. Avoid use during breastfeeding.  

Pregnancy category: 

• Category A: Satisfactory and well-controlled studies show no evidence of risk to the fetus in the first trimester or the later trimester. 
• Category B: There is no evidence of risk to the fetus found in animal reproduction studies and there are not enough studies on pregnant women. 
• Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for an effect in humans, care must be taken for potential risks in pregnant women. 
• Category D: There is adequate data available with sufficient evidence of human fetal risk from various platforms, but despite potential risks may be used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh risks over benefits. These category drugs should be prohibited for pregnant women. 
• Category N: There is no data available for the drug under this category. 

Pharmacology: 

doxycycline is a broad-spectrum antibiotic that belongs to the tetracycline class of drugs. It works by inhibiting bacterial protein synthesis by binding to the 30S ribosomal subunit, preventing the attachment of aminoacyl-tRNA molecules to the mRNA-ribosome complex, and thereby blocking the elongation phase of protein synthesis. This ultimately leads to inhibition of bacterial growth and proliferation. 

doxycycline has a long half-life of approximately 18-22 hours, which allows for less frequent dosing compared to other antibiotics. It is well absorbed after oral administration and reaches peak concentrations within 2-4 hours. It can also be administered intravenously in severe infections. 

doxycycline has broad-spectrum activity against both Gram-positive and Gram-negative bacteria, as well as against certain protozoa. It is commonly used to treat a wide range of infections, including respiratory tract infections, urinary tract infections, sexually transmitted infections, skin and soft tissue infections, and certain types of bacterial diarrhea. 

Pharmacodynamics 

The pharmacodynamics of doxycycline involve its ability to inhibit bacterial protein synthesis. doxycycline binds to the 30S ribosomal subunit of bacteria, preventing the attachment of aminoacyl-tRNA molecules to the mRNA-ribosome complex, and thereby blocking the elongation phase of protein synthesis. This ultimately leads to inhibition of bacterial growth and proliferation. 

doxycycline has broad-spectrum activity against both Gram-positive and Gram-negative bacteria, as well as against certain protozoa. Its bacteriostatic effect is concentration-dependent, meaning that higher concentrations of the drug are required to achieve a bactericidal effect. doxycycline is also effective against bacteria that are resistant to other antibiotics, including beta-lactam antibiotics. 

In addition to its antibacterial activity, doxycycline has been shown to have anti-inflammatory and immunomodulatory effects. It has been suggested that doxycycline inhibits the production of pro-inflammatory cytokines and chemokines and may also modulate the activity of immune cells such as macrophages and T cells. These effects may contribute to its efficacy in the treatment of certain inflammatory conditions such as acne and rosacea. 

Pharmacokinetics 

Absorption 

Completely absorbed orally, is reduced when taken with food or milk 

The peak serum concentration is achieved in 1.5-4 hr 

The bioavailability is reduced at high pH 

Distribution 

Protein-bound is 90% 

Metabolism 

It is metabolised in liver 

Elimination and excretion 

The half-life is achieved in 15-25 hours 

The drug is excreted 23%in urine and 30% in feces 

Administration: 

doxycycline is an antibiotic that can be administered in several ways, depending on the intended use and severity of the infection: 

• Oral tablets or capsules: doxycycline is available in oral tablets or capsules that can be taken with a full glass of water. The dosage and administration schedule may vary depending on the specific condition being treated, the patient’s age and weight, and other individual factors. It is important to take the medication as directed by the healthcare provider or on the medication label. 
• Intravenous (IV) infusion: doxycycline can be administered intravenously for severe infections or when oral administration is not possible. This is usually done in a hospital or clinic setting under the supervision of a healthcare provider. 
• Topical application: doxycycline can also be used topically in the form of creams, gels, or ointments for the treatment of certain skin infections. 

Patient information leaflet 

Generic Name: doxycycline 

Pronunciation: DOX-i-SYE-kleen 

Why do we use doxycycline? 

doxycycline is a broad-spectrum antibiotic that is commonly used to treat bacterial infections, including sexually transmitted infections (STIs). The reason why doxycycline is often used for STIs is because it is effective against a variety of bacteria that can cause these infections, such as chlamydia, gonorrhea, and syphilis. 

Chlamydia and gonorrhea are two of the most common STIs and are caused by bacterial infections. doxycycline is often used to treat these infections because it can target the bacteria responsible for the infections and stop them from replicating and spreading. Syphilis, another bacterial STI, can also be treated with doxycycline, especially in cases where penicillin (the preferred treatment) is not an option. 

In addition to its effectiveness against bacterial STIs, doxycycline is also preferred because it is relatively safe, well-tolerated, and can be taken orally. It is also relatively affordable and widely available, making it a practical choice for treating STIs in many regions of the world.