Doxycycline

Doxycycline is a broad-spectrum antibiotic belonging to the tetracycline class. It is used to treat a variety of infectious diseases, including respiratory infections, urinary tract infections, skin infections, and sexually transmitted diseases such as chlamydia and gonorrhea. Doxycycline is also used to prevent and treat malaria, as well as to prevent infections after tick bites.

Doxycycline works by inhibiting protein synthesis in microbial cells, which prevents their growth and reproduction. This antibiotic is taken orally and is known for its effectiveness and ability to act against a wide range of bacterial organisms.

However, like any antibiotic, doxycycline should be taken strictly as prescribed by your doctor to avoid the development of bacterial resistance to antibiotics and minimize the risk of side effects.

Indications Doxycycline

1. Respiratory infections: Treatment of bronchitis, pneumonia, and other respiratory tract infections.
2. Urinary tract infections: Treatment of cystitis, urethritis and other urinary tract infections.
3. Skin and soft tissue infections: Treatment of acne, rosacea, impetigo and other skin infections.
4. Sexually transmitted infections: Treatment of chlamydia, gonorrhea and syphilis.
5. Gastrointestinal infections: Treatment of some forms of diarrhea, including that caused by bacteria.
6. Malaria: Prevention and treatment of malaria in combination with other drugs.
7. Infection prevention: Prevention of infections after animal or tick bites.
8. Lyme disease: Treatment of early stages of Lyme disease.
9. Tropical infections: Treatment of tropical infections such as typhoid, brucellosis and others.

Release form

1. Capsules: One of the most common forms, usually containing 100 mg of active substance. The capsules are swallowed whole and washed down with water.
2. Tablets: Also a commonly used form, which may be preferable for those who have difficulty taking capsules.
3. Dissoluble tablets: These tablets are dissolved in water before use, which may be convenient for patients who have difficulty swallowing solid dosage forms.
4. Injection solution: Doxycycline is also available in injection form, which can be used in clinical settings, especially for severe infections.
5. Oral suspension: This form is suitable for children and adults who have difficulty taking tablets or capsules.

Pharmacodynamics

1. Inhibition of bacterial protein synthesis: Doxycycline binds to bacterial ribosomes and inhibits the functioning of the ribosomal system, which leads to disruption of protein synthesis and inhibition of bacterial growth and reproduction.
2. Bacteriostatic effect: This means that doxycycline stops the growth and reproduction of bacteria, but does not completely destroy them. The body has time to fight the infection.
3. Effects on intracellular parasites: Doxycycline is effective against intracellular bacteria, such as Chlamydia and Mycoplasma, due to its ability to penetrate and accumulate in cells.
4. Anti-inflammatory effect: In addition to its antibacterial effect, doxycycline has some anti-inflammatory effects, which may be useful in the treatment of infections accompanied by inflammation.
5. Long half-life: Doxycycline has a long half-life, which allows it to achieve effective concentrations of the drug in the body even when taken once a day.

Doxycycline has activity against a wide range of bacteria, including many gram-positive and gram-negative organisms:

• Staphylococci: Including Staphylococcus aureus, including methicillin-resistant strains (MRSA).
• Streptococci: Including Streptococcus pneumoniae and Streptococcus pyogenes (group A beta-hemolytic streptococci).
• Enterococcus faecalis: However, some strains of Enterococcus faecalis may be resistant to doxycycline.
• Neisseria gonorrhoeae: However, in recent years, resistance has emerged in some strains.
• Haemophilus influenzae: Including beta-lactamase-positive strains.
• Moraxella catarrhalis: Doxycycline may be effective against some strains.
• Mycoplasma and Chlamydia: These intracellular bacteria are usually sensitive to doxycycline.
• Rickettsia, Borrelia, and others: Doxycycline is also used to treat rickettsial diseases, borreliosis (including Lyme borreliosis), and other infections caused by anaerobic organisms.

Pharmacokinetics

1. Absorption: Doxycycline is usually administered orally as tablets or capsules. After taking the drug, it is quickly and almost completely absorbed from the gastrointestinal tract, although its absorption may be reduced when concomitantly ingesting food, especially one rich in calcium.
2. Distribution: Doxycycline is widely distributed in tissues and organs of the body, including skin, lungs, liver, kidneys, spleen, bones and others. It also crosses the placental barrier and is excreted into breast milk.
3. Metabolism: Doxycycline is slightly metabolized in the liver. It is mainly excreted unchanged from the body through the kidneys and, to a lesser extent, through the intestines.
4. Elimination: The plasma half-life of doxycycline is approximately 12-25 hours, allowing it to be administered as a single or once-daily dose for many infectious diseases.
5. Protein binding: Doxycycline binds to plasma proteins to a small extent, approximately 80-90%.

Dosing and administration

General recommendations:

1. Adults and children over 12 years of age:

   • For common infections, the usual starting dose is 200 mg on the first day of treatment (divided into two doses of 100 mg every 12 hours), followed by 100 mg daily for the duration of treatment. In some cases, the dose may remain 200 mg per day, depending on the doctor's recommendations.
   • For more severe infections, the dose may need to be increased to 200 mg per day throughout the course of treatment.

2. Children under 12 years old:

   • Doxycycline is not generally recommended for children under 12 years of age due to the potential for negative effects on tooth and bone development.

Specific conditions:

• Malaria prevention: Doxycycline is used at a dose of 100 mg per day, starting 1-2 days before entering a malarial region, throughout the stay and continuing for 4 weeks after departure.
• Treatment of acne: The usual dose is 100 mg per day, the course of treatment may vary in duration depending on the doctor's recommendations.
• Atypical infections such as chlamydia or mycoplasma: Longer treatment with doxycycline 100 mg twice daily may be required.

Admission tips:

• Doxycycline should be taken with plenty of water to avoid esophageal irritation.
• It is best to take the medication with or immediately after a meal to reduce stomach irritation, but avoid taking it with dairy products as calcium may interact with doxycycline, reducing its effectiveness.
• Do not take doxycycline immediately before bed.

Use Doxycycline during pregnancy

The use of doxycycline during pregnancy is not traditionally recommended due to the potential risks to fetal development associated with other tetracyclines, such as impaired bone formation and tooth staining. However, recent research is beginning to reconsider this position:

1. A 2016 review article highlights that doxycycline has significant bioavailability and a broad therapeutic spectrum, and its benefits may outweigh potential risks, especially in the treatment of diseases such as typhus and murine typhus, which can seriously affect pregnancy outcomes in the Southeast. Asia. This study did not find a direct link between doxycycline use and teratogenic effects or tooth staining in children, which makes it different from other tetracyclines (Cross et al., 2016).
2. Another study from 2022 used the FDA's adverse effects database to describe cases of doxycycline use during pregnancy. The results show limited data on the safety of doxycycline for rickettsial infections during pregnancy, but support the need for additional research to more accurately assess its safety (Kaundinnyayana & Kamath, 2022).

Thus, although doxycycline has traditionally been considered contraindicated during pregnancy due to potential risks to the fetus, new evidence suggests that its use may be justified in certain clinical situations where the benefits outweigh the potential risks. Always consult your doctor before starting treatment with doxycycline during pregnancy.

Contraindications

1. Allergy to doxycycline or other tetracyclines. Reactions may include skin rash, itching, angioedema, and in rare cases, anaphylactic shock.
2. Pregnancy, especially in the second and third trimesters. Doxycycline can affect the development of fetal bones and teeth, which can cause teeth to be permanently discolored yellow-gray or brown and slow bone growth.
3. Breastfeeding period. Doxycycline can pass into breast milk and may adversely affect the growth and development of teeth and bones in infants.
4. Children up to 8 years old. Just as in pregnant women, doxycycline use in children can cause permanent teeth staining and problems with bone development.

Doxycycline should also be used with extreme caution in the presence of conditions such as:

• Liver failure. Impaired liver function may affect the metabolism of doxycycline, requiring dosage adjustment.
• Mycoses (fungal infections). Doxycycline may worsen these conditions by suppressing normal microflora.

Side effects Doxycycline

1. Gastrointestinal disorders: Nausea, vomiting, diarrhea and heartburn are common side effects. These symptoms may be relieved by taking the medication with food.
2. Photosensitivity: Doxycycline may increase skin sensitivity to sunlight, causing mild sunburn even with short-term sun exposure.
3. Fungal infections: Like other antibiotics, doxycycline can disrupt the body's normal flora, promoting the development of candidiasis (thrush), especially in women.
4. Changes in tooth color: Long-term use of doxycycline may cause tooth staining, especially in children.
5. Allergic reactions: Skin rashes, itching, angioedema (swelling of the deep layers of the skin, sometimes accompanied by difficulty breathing) and other serious allergic reactions are possible.
6. Increased intracranial pressure: This is a less common but serious side effect that can cause headaches, visual disturbances, and even optic nerve impingement.
7. Effects on the liver: In rare cases, doxycycline may cause elevated liver enzymes, indicating liver strain or damage.

Overdose

1. Gastrointestinal Disorders: An increased dose of doxycycline may increase gastrointestinal side effects such as nausea, vomiting, diarrhea, and abdominal discomfort.
2. Hepatotoxicity: Possible development of liver failure, especially in the presence of pre-existing liver problems.
3. Photosensitivity: Hypersensitivity to sunlight may cause severe burns if exposed to skin for long periods of time.
4. Effects on the kidneys: Overdose may have a negative effect on kidney function, especially in people with pre-existing kidney problems.
5. Hypertoxic effects: Serious side effects such as intracerebral hypertensive crises or cardiac arrhythmias may develop.
6. Dysbacteriosis: An overdose can disrupt the intestinal microflora, causing dysbiosis and increasing the risk of developing intestinal infections.

Interactions with other drugs

1. Antacids, drugs containing calcium, magnesium, iron or aluminum: These drugs may reduce the absorption of doxycycline from the gastrointestinal tract. Therefore, they should be taken at least 2 hours before or after taking doxycycline.
2. Medicines containing vitamins, minerals or other trace elements: Similar to antacids, drugs containing these elements may interfere with the absorption of doxycycline.
3. Medicines that affect blood formation (anticoagulants): Doxycycline may increase the effect of anticoagulants, which may lead to an increased risk of bleeding. In such cases, dose adjustment of the anticoagulant may be necessary.
4. Drugs that increase photosensitivity: Doxycycline may increase the photosensitivity of the skin when used simultaneously with drugs such as retinoids, tetracyclines, and others. This may lead to an increased risk of sunburn and skin reactions.
5. Drugs that affect the liver: Doxycycline may increase the hepatotoxicity of some drugs that affect the liver. Therefore, you need to be careful when using these drugs simultaneously.
6. Drugs that affect the central nervous system: Doxycycline may increase the sedative effects of other drugs that affect the central nervous system, such as benzodiazepines, hypnotics, or alcohol.