Doxycycline 100 Capsule

Q1: What infections does Doxycycline 100mg treat?

Doxycycline 100mg treats a wide range of infections including community-acquired pneumonia, bronchitis, sinusitis, moderate-to-severe acne vulgaris, chlamydia and non-gonococcal urethritis, pelvic inflammatory disease, Lyme disease (Borrelia), Rocky Mountain spotted fever, brucellosis, Q fever, and is used for malaria prophylaxis in high-risk travel zones.

Q2: How does Doxycycline work to kill bacteria?

Doxycycline binds to the 30S ribosomal subunit of bacteria, blocking attachment of aminoacyl-tRNA to the ribosomal acceptor site. This prevents addition of new amino acids to growing peptide chains, halting protein synthesis and stopping bacterial replication. It is bacteriostatic, meaning it relies on the host immune system to clear bacteria that can no longer replicate.

Q3: What is the correct dose and frequency for Doxycycline 100mg?

For most bacterial infections: 100mg twice daily for 7–14 days. For chlamydia: 100mg twice daily for 7 days. For Lyme disease (early stage): 100mg twice daily for 10–21 days. For acne: 100mg once daily for 3–6 months under physician supervision. For malaria prophylaxis: 100mg once daily starting 1–2 days before entry into endemic area, continuing throughout stay and for 4 weeks after return.

Q4: How long does Doxycycline 100mg take to work?

For acute bacterial infections such as pneumonia or chlamydia, clinical improvement is typically seen within 48–72 hours. For acne, noticeable reduction in inflammatory lesions usually takes 6–8 weeks of consistent daily use, with optimal skin improvement at 12 weeks. Malaria prophylaxis requires the drug to be established in the system before exposure.

Q5: Should I take Doxycycline with food?

Yes. Doxycycline 100mg should be taken with food or milk to significantly reduce the risk of nausea and oesophageal irritation. Unlike older tetracyclines, doxycycline absorption is not substantially reduced by food. However, avoid taking it simultaneously with dairy products, antacids, iron supplements, or calcium — these reduce absorption and should be taken 2+ hours apart.

Q6: Why do I need to stay upright after taking Doxycycline?

Doxycycline capsules can cause oesophageal ulceration if they dissolve in contact with the oesophageal lining rather than passing through to the stomach. Swallow each capsule with a full glass of water while sitting or standing upright, and remain upright for at least 30 minutes afterwards to ensure the capsule reaches the stomach.

Q7: Can Doxycycline make me sensitive to sunlight?

Yes. Photosensitivity is one of the most commonly reported side effects of doxycycline. Sun exposure while taking doxycycline can cause exaggerated sunburn reactions, skin reddening, and blistering even with relatively brief exposure. Use a broad-spectrum SPF 30+ sunscreen daily, wear protective clothing, and avoid prolonged sun or UV exposure throughout the entire treatment course.

Q8: What are the side effects of Doxycycline 100mg?

Common side effects include nausea, diarrhoea, oesophageal irritation or heartburn, headache, and photosensitivity. Less common effects include skin or nail discolouration and vaginal thrush in women. Serious but rare effects include benign intracranial hypertension, severe skin reactions (Stevens-Johnson Syndrome), hepatotoxicity, and Clostridioides difficile colitis.

Q9: Is Doxycycline 100mg safe for children?

Doxycycline is NOT recommended for children under 8 years of age. Like all tetracyclines, it binds to calcium in developing teeth, causing permanent grey-brown tooth discolouration, and can impair long-bone growth. In children aged 8 and older, doxycycline is used for specific indications such as Rocky Mountain spotted fever and Lyme disease under physician supervision.

Q10: Can pregnant women take Doxycycline 100mg?

Doxycycline is contraindicated in pregnancy (all trimesters) and during breastfeeding. Tetracyclines cross the placenta and can cause permanent tooth discolouration, enamel hypoplasia, and retardation of skeletal development in the fetus. A physician should prescribe an alternative safe antibiotic during pregnancy.

Q11: How should Doxycycline 100mg capsules be stored?

Store at room temperature between 15°C and 30°C, away from moisture and direct sunlight. Keep in the original blister packaging — humidity and light degrade doxycycline. Do not store in a bathroom cabinet due to humidity. Keep out of reach of children. Do not use after the expiry date.

Q12: Do I need a prescription for Doxycycline 100mg?

Yes. Doxycycline is a prescription-only antibiotic in most countries. A healthcare provider must confirm the bacterial infection or malaria prophylaxis indication before prescribing. For long-term use in acne, regular medical review is required to monitor efficacy, side effects, and the continued need for antibiotic therapy.