Doxycycline

Overview of Doxycycline

Doxycycline is a tetracycline antibiotic that fights bacteria in the body. It is used to treat many different bacterial infections, such as acne, urinary tract infections, intestinal infections, respiratory infections, eye infections, gonorrhea, chlamydia, syphilis, periodontitis (gum disease), and others. It is also used to prevent malaria and treat anthrax exposure or other conditions as determined by a healthcare provider.

Pharmacological Properties

Doxycycline works by inhibiting protein synthesis in susceptible bacteria, thereby stopping bacterial growth. This antibiotic is bacteriostatic, which means it doesn’t necessarily kill bacteria directly but prevents them from multiplying.

Dosage Forms and Strengths

Doxycycline is available in several forms, including immediate-release tablets, delayed-release tablets, capsules, and a liquid suspension. It is also available in various strengths, typically ranging from 20 mg to 100 mg for tablets and capsules. The intravenous form is also available for inpatient use in hospitals.

Indications for Use

Doxycycline is indicated for the treatment of various infections as mentioned earlier. It is particularly effective against infections caused by tetracycline-sensitive organisms and is frequently used for the management of acne vulgaris and rosacea.

Dosing Guidelines

The dosage of doxycycline depends on the severity and type of infection. For adults, the typical dose ranges from 100 mg to 200 mg per day, with the dosage divided into one or two daily doses. For children above eight years of age and weighing less than 45 kg, the recommended dose is 2.2 mg/kg given twice a day. Treatment duration varies based on infection and response to therapy.

Administration Instructions

Doxycycline should be taken with a full glass of water to prevent esophageal irritation or ulceration. It is advised to be taken while sitting up or standing. The drug can be taken with or without food, but absorption is reduced when taken with dairy products or antacids. Delayed-release tablets should be swallowed whole without chewing or crushing them.

Drug Interactions

Doxycycline can interact with other medications, potentially affecting the efficacy of either doxycycline or the other medications. Examples include antacids containing magnesium or calcium, iron supplements, laxatives containing magnesium, and calcium channel blockers. Barbiturates, carbamazepine, and phenytoin may decrease the half-life of doxycycline.

Pharmacokinetics

After oral administration, doxycycline is well absorbed and its absorption is minimally affected by the presence of food in the stomach. Its bioavailability is approximately 90-100%. Doxycycline has a large volume of distribution, indicating its widespread distribution in tissues. It is excreted primarily in the feces and has a half-life of about 16 to 22 hours based on normal renal function.

Use in Specific Populations

Pregnancy: Doxycycline is classified under FDA pregnancy category D. Usage is contraindicated as it may pose risks to the fetus when administered to pregnant women, particularly in the second and third trimesters.

Breastfeeding: Doxycycline can pass into breast milk and may affect bone and tooth development in a nursing infant. The use while nursing is discouraged unless the benefits of therapy are greater than the potential risks.

Pediatric use: Doxycycline should not be used in children under the age of 8 unless other appropriate drugs are ineffective or contraindicated, as doxycycline can cause permanent yellowing or graying of teeth in children.

Geriatric use: No adjustments to the standard adult dosage are generally necessary for elderly patients. However, particular attention should be given to renal function as this can be compromised with age.

Monitoring Parameters

Renal function, hepatic function, and complete blood counts should be monitored periodically in patients receiving long-term therapy to watch for potential adverse effects. For those using doxycycline for long periods, such as for the treatment of acne, monitoring for signs of candida overgrowth or photosensitivity is recommended.

Adverse Reactions

Common adverse reactions of doxycycline include nausea, vomiting, diarrhea, rash, and photosensitivity. Gastrointestinal side effects are more frequent with higher doses. In some cases, intracranial hypertension, autoimmune disorders like lupus-like syndrome, and hypersensitivity reactions including anaphylaxis and angioedema may occur.

Overdose Management

In the case of an overdose, symptomatic and supportive measures should be undertaken. Because doxycycline is not significantly removed by dialysis, treatment options are limited in overdose situations beyond general supportive measures such as maintaining oxygenation and hydration and monitoring renal function and vital signs.