Medical

Difference Between Amoxicillin and Doxycycline

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Main Difference

The main difference between Amoxicillin and Doxycycline is that Amoxicillin is a penicillin antibiotic, and Doxycycline is tetracycline antimicrobial.

Amoxicillin vs. Doxycycline

Amoxicillin is penicillin, and it is a bactericidal drug, and Doxycycline is a tetracycline, and it is a bacteriostatic drug. Amoxicillin shows its pharmacological action by inhibiting cell wall synthesis, and Doxycycline shows its pharmacological action by inhibiting protein synthesis.

Amoxicillin is effective against bacteria and those bacteria which have a cell wall and are rapidly dividing and Doxycycline is effective against a broad range of microbes. Amoxicillin is designed to give orally, although its parenteral preparations are available, and Doxycycline is equally effective orally and through intravenous injections.

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Amoxicillin is not distributed to CSF in ordinary conditions, but in inflammatory conditions of meninges, it can be distributed to CSF, and Doxycycline is distributed to CSF in normal conditions of meninges. Amoxicillin finds no use in the prophylaxis of malaria, and Doxycycline is used to prevent malaria although it finds no use in the treatment of malaria.

Amoxicillin can give with dairy products, and Doxycycline can not be given with dairy products because dairy products decrease their absorption, and similar products containing magnesium and aluminum decrease the absorption of Doxycycline.

Amoxicillin, when prescribed to patients with kidneys then its dose is adjusted and Doxycycline when prescribed to patients with kidneys then adjustment of dose is not so important. Amoxicillin is excreted via a secretory system of the kidney or by glomerular filtration Doxycycline is eliminated by bile in feces.

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Amoxicillin does not cause phototoxicity when exposed to sun or ultraviolet rays, and Doxycycline causes phototoxicity when exposed to sun or ultraviolet rays. Amoxicillin does not cause vestibular dysfunction, and Doxycycline causes vestibular dysfunction.

Amoxicillin can be used in children under 8 years of age, and Doxycycline cannot be used in children under 8 years of age. Amoxicillin can be taken on an empty stomach, and Doxycycline cannot be taken on an empty stomach.

Comparison Chart

AmoxicillinDoxycycline
Amoxicillin is a widely effective antibiotic and belongs to penicillins.Doxycycline is classified in antibiotics as a broad-spectrum drug belongs to tetracyclines.
Mechanism
Cell wall synthesis inhibitorProtein synthesis inhibitor
Route of Administration
ParentalOral
Effect on the absorption of food
No effectNo effect but dairy products decrease absorption
Distribution of body fluids
Does not distribute in CSFDistribute in CSF
Contraindications
Hypersensitivity reactionPregnant women

Breastfeeding women

Children under 8 years of age

What is Amoxicillin?

Amoxicillin is semi-synthetic penicillin and is a close relative of ampicillin chemically and pharmacologically. Amoxicillin is penicillinase-susceptible and is an acid-stable drug. Amoxicillin is designed for oral use.

The peak plasma concentration of the Amoxicillin is reached after 2hrs of administration of the drug. When a dose of 250mg of Amoxicillin is administered, the peak plasma concentration is 4µg/ml.

The presence of food in stomach does not affect the absorption of Amoxicillin. Amoxicillin acts of attaching to the cell wall of susceptible bacteria and leads to lysis of the cell wall hence, Amoxicillin is a bactericidal compound. 20% Amoxicillin is protein-bound in plasma.

Amoxicillin is effective against many bacterial infections, which include the infection caused by the pneumococci, Neisseria gonorrhoeae streptococci, enterococci, Haemophilus influenza, Proteus mirabilis, Escherichia coli, Helicobacter pylori Neisseria meningitides.

Amoxicillin finds its therapeutic use in infections of the middle ear, skin, and urinary tract and also treats sore throat and pneumonia. As Amoxicillin can be degraded by the beta-lactamase, so it is given in combination with clavulanic acid, which is a beta-lactamase inhibitor. Amoxicillin is also given in combination with gentamicin for severe infections in infants.

Amoxicillin causes a number of unwanted effects like rash and nausea and increases the risk of yeast infections. Some other side effects include diarrhea, increased vaginal discharge, headache, and black or hairy tongue.

Amoxicillin must not be given to patients who are allergic to penicillin. Amoxicillin dose should be adjusted in kidney patients. Amoxicillin is safe to use in pregnancy and in breastfeeding mothers. Some children and adults develop a rash after 72hrs of taking Amoxicillin this rash is called the Amoxicillin rash this rash is sometimes also seen in the case of ampicillin.

What is Doxycycline?

Doxycycline belongs to tetracyclines and is used to treat infections caused by bacteria and parasites. Doxycycline, like other tetracyclines, has 4 fused rings with a system of conjugated double bonds. Doxycycline is bacteriostatic and inhibits further multiplication of bacteria by inhibiting protein synthesis.

Doxycycline is a broad-spectrum drug and attaches to the 30S ribosomal subunit, thus inhibiting protein synthesis. This ultimately causes the prevention of the addition of amino acids to the polypeptide chain.

So, the process of formation of the new proteins stopped. As multiplication of bacteria does not occur and new bacteria are not formed so this allows the immune system to remove bacteria. Doxycycline can be taken orally and through IV injections.

Doxycycline easily enters the cells because of its high lipophilic property. Doxycycline is absorbed easily when taken orally. The volume of distribution is large in case of Doxycycline . Doxycycline has long elimination half-life because due to lipophilic property it is reabsorbed both in the gastrointestinal tract and renal tubules.

In renal failure patients, Doxycycline is excreted in feces because of a compensatory mechanism hence it does not accumulate in kidneys in patients. Food does not affect its absorption. Acidic PH makes Doxycycline metal ion complexes unstable, so more drug enters the duodenum.

Doxycycline causes a number of unwanted effects like gastrointestinal upset. When taken orally, it causes pill esophagitis because of three reasons including less fluid intake with pill, difficult swallowing, and mobility problem.

Doxycycline when taken for malarial prophylaxis causes erythematous, which is a rash occuring in those parts of body which are exposed to sun. On discontinuation of Doxycycline therapy, the rash resolves.

Doxycycline has a number of therapeutic uses. Doxycycline is used in the treatment of early stages of Lyme disease, cholera, acne, bacterial pneumonia, syphilis, and chlamydia infections. Doxycycline prevents malaria and is used as antianthelmintic.

Key Differences

  1. Amoxicillin is penicillin whereas Doxycycline is tetracycline.
  2. Amoxicillin is cell wall synthesis inhibitor on the other hand Doxycycline is Protein synthesis inhibitor.
  3. Amoxicillin does not distributes in CSF Conversely, Doxycycline distributes in CSF.
  4. Amoxicillin is bactericidal on the flip side Doxycycline is bacteriostatic.
  5. Amoxicillin ineffective against organisms which do not have cell wall whereas Doxycycline effective against organisms which do not have or have a cell wall.
  6. Amoxicillin is ineffective against those bacteria which are not diving, on the other hand, Doxycycline is effective against such bacteria.
  7. Amoxicillin is not used in prophylaxis of the malaria on the flip side Doxycycline is used in prophylaxis of the malaria. Amoxicillin Doxycycline
  8. Amoxicillin can cause amoxicillin rash while Doxycycline can cause erythematous state when taken for prophylaxis of malaria.
  9. Amoxicillin is ineffective against parasites on the other hand Doxycycline is effective against parasites.
  10. Amoxicillin can be given to patients under 8 years of age on the flip side Doxycycline can not be given to patients under 8 years of age.
  11. Amoxicillin can be taken on the stomach is empty, whereas Doxycycline can not be taken on the stomach is empty.
  12. Amoxicillin is found to cause any burn when a patient on treatment is exposed to sun, or ultraviolet rays on the other hand Doxycycline causes phototoxicity when a patient on treatment is exposed to sun or ultraviolet rays.
  13. Amoxicillin does not interact with dairy foods or trivalent or tetravalent ions conversely Doxycycline interacts with dairy foods or trivalent or tetravalent ions as they lead to less absorption of Doxycycline.
  14. Amoxicillin can be taken by pregnant women on the flip side Doxycycline is contraindicated in pregnancy.

Conclusion

The conclusion of the above discussion is that both Amoxicillin and Doxycycline are antimicrobials and belong to two different groups of pharmacological classes and have different antimicrobial spectrum.

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Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White