Usage
Tetracycline is a broad-spectrum antibiotic prescribed for various bacterial infections, including those of the respiratory tract, skin, intestines, urinary tract, and sexually transmitted infections like syphilis, gonorrhea, and chlamydia. It is also used in the treatment of acne, rosacea, and some protozoal infections. Its pharmacological classification is an antibiotic, specifically a protein synthesis inhibitor. Tetracycline exerts its bacteriostatic effect by inhibiting protein synthesis within the bacterial ribosome, preventing the growth and spread of susceptible bacteria.
Alternate Names
While “tetracycline” is the generic name, several brand names exist, such as Sumycin, Panmycin, and Tetralan. There are also other tetracycline-class antibiotics with different chemical structures, like doxycycline and minocycline, which are sometimes referred to as tetracyclines.
How It Works
Pharmacodynamics: Tetracycline inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit, blocking the attachment of aminoacyl-tRNA to the mRNA-ribosome complex. This prevents the addition of amino acids to the growing polypeptide chain, ultimately halting bacterial protein synthesis and leading to bacteriostasis.
Pharmacokinetics:
- Absorption: Absorption occurs primarily in the stomach and upper small intestine. It is affected by food, especially dairy products, antacids, and iron supplements, which can reduce absorption.
- Distribution: Tetracycline is widely distributed throughout the body, including into tissues and organs, but penetration into the cerebrospinal fluid is poor. It can cross the placenta and is found in breast milk.
- Metabolism: Tetracycline undergoes minimal metabolism in the liver.
- Elimination: Primarily excreted unchanged in the urine through glomerular filtration and to a lesser extent in the feces via biliary excretion. Dose adjustment may be necessary in patients with renal impairment.
Dosage
Standard Dosage
Adults:
Standard dosage is 250 to 500 mg orally every 6 hours or 500mg to 1g every 12 hours. Dosage may need adjustments for severe infections.
Children:
For children older than 8 years, the usual dose is 25-50 mg/kg/day orally divided every 6 hours, not to exceed 3g/day. For children younger than 8 years old, tetracycline usage is generally contraindicated due to the increased risk of permanent teeth discoloration and potential bone growth impairment.
Special Cases:
- Elderly Patients: Standard adult doses are typically used, but careful monitoring for renal function is essential.
- Patients with Renal Impairment: Dose adjustments are needed for patients with renal dysfunction, usually by extending the dosing interval. Consultation with a nephrologist is recommended.
- Patients with Hepatic Dysfunction: Tetracycline is metabolized minimally in the liver; hence, significant dose adjustments are usually not necessary. Monitor liver function periodically.
- Patients with Comorbid Conditions: Caution should be observed for co-existing conditions such as diabetes, cardiovascular disease, and any history of gastrointestinal issues.
Clinical Use Cases
Tetracycline is not typically recommended as a first-line agent for clinical cases related to intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. Its role in these settings is usually reserved for rare cases where specific sensitivities dictate its use due to resistance to other antibiotics.
Dosage Adjustments
Renal dysfunction requires reducing the total dosage and/or increasing the interval between doses, in line with specific creatinine clearance measurements and clinical response.
Side Effects
Common Side Effects:
Nausea, vomiting, diarrhea, loss of appetite, mouth sores, black hairy tongue, sore throat, dizziness, headache, and rectal discomfort.
Rare but Serious Side Effects:
Nail discoloration, muscle pain, difficulty swallowing, signs of kidney problems, brown/gray tooth discoloration, numbness/tingling of hands/feet, unusual tiredness, new signs of infection, hearing changes, easy bruising/bleeding, signs of liver disease. Rarely, intracranial hypertension (IH) can occur.
Long-Term Effects:
Permanent teeth discoloration and enamel hypoplasia can occur with prolonged use, particularly in children under 8 years of age.
Adverse Drug Reactions (ADR):
Severe allergic reactions (anaphylaxis), angioedema, Stevens-Johnson syndrome, toxic epidermal necrolysis.
Contraindications
Hypersensitivity to tetracyclines, pregnancy (especially the second and third trimesters), breastfeeding, children under 8 years of age, severe renal impairment.
Drug Interactions
Tetracycline interacts with various medications, including:
- Antacids, iron supplements, calcium supplements: Reduce tetracycline absorption.
- Oral contraceptives: May reduce efficacy of oral contraceptives.
- Anticoagulants: May enhance anticoagulant effects.
- Retinoids (e.g., acitretin): Increased risk of intracranial hypertension.
- Methotrexate: Increased risk of methotrexate toxicity.
Pregnancy and Breastfeeding
Tetracycline is contraindicated in pregnancy due to the risk of permanent teeth discoloration and potential effects on bone growth in the developing fetus. Short-term use during breastfeeding might be acceptable in some situations, but alternative antibiotics are generally preferred to minimize potential risks to the infant.
Drug Profile Summary
- Mechanism of Action: Inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit.
- Side Effects: Nausea, vomiting, diarrhea, photosensitivity, tooth discoloration. Serious side effects: hepatotoxicity, intracranial hypertension.
- Contraindications: Pregnancy, breastfeeding, children under 8, hypersensitivity to tetracyclines.
- Drug Interactions: Antacids, iron, calcium, oral contraceptives, anticoagulants, retinoids.
- Pregnancy & Breastfeeding: Contraindicated.
- Dosage: Adults: 250-500 mg every 6 hours. Children (over 8 years): 25-50 mg/kg/day divided every 6 hours.
- Monitoring Parameters: Renal function, liver function, signs of infection, and clinical response.
Popular Combinations
Tetracycline is sometimes combined with other antibiotics for specific infections, but it is important to consider potential drug interactions and adverse effects.
Precautions
Assess for allergies, renal and hepatic function, and any history of photosensitivity. Caution patients about sun exposure and the need to use sun protection. Advise against concomitant use with antacids, iron, or calcium supplements.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Tetracycline?
A: Adults: 250-500 mg orally every 6 hours. Children (over 8 years): 25-50 mg/kg/day orally divided every 6 hours. Adjustments are necessary for renal impairment.
Q2: What are the common side effects?
A: Nausea, vomiting, diarrhea, abdominal pain, photosensitivity, and tooth discoloration.
Q3: Can Tetracycline be used during pregnancy?
A: No, Tetracycline is contraindicated during pregnancy due to the risk of adverse effects on fetal development.
Q4: How does Tetracycline work?
A: Tetracycline inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit.
Q5: What are the serious side effects to watch out for?
A: Severe allergic reactions, hepatotoxicity, intracranial hypertension, and superinfections.
Q6: What should patients avoid while taking Tetracycline?
A: Sun exposure, dairy products, antacids, iron supplements, and calcium supplements.
Q7: Is Tetracycline effective against viral infections?
A: No, tetracycline is only effective against bacterial infections.
Q8: What if a patient misses a dose?
A: Take the missed dose as soon as remembered, unless it is almost time for the next dose. Do not double the dose.
Q9: How long should Tetracycline treatment typically last?
A: Treatment duration depends on the type and severity of infection, usually ranging from 7 to 21 days or longer in specific cases like acne or rosacea.
Q10: What interactions exist between iron supplements and Tetracycline?
A: Iron reduces Tetracycline’s absorption and consequently reduces its efficacy. Separate the intake of both medications by a few hours.
