Doxycycline: Contraindications, Properties And Benefits

Doxycycline is an antibiotic that belongs to the group of “tetracyclines” , which is responsible for preventing the growth and proliferation of bacteria, both from the group of ” Gram positive” and ” Gram negative” which are present in serious conditions , like, for example: pneumonia.

In short , Doxycycline is used to treat diseases of bacterial origin in the body; including pneumonia and the various diseases of the respiratory system, infections in the reproductive system, the eyes and the different diseases spread by external parasites such as ticks, lice and fleas.

It is also used to combat acne, since this is caused by the proliferation of bacteria of the order ” Propionibacterium Acnes” in the papules present on the skin, likewise, it can be used in the form of injection to prevent attacks of a biological order. , being applied to suspicious people.

On the other hand, it also serves as a substituent for Penicillin , for all those people who are allergic to said compound, especially when it comes to food poisoning or diseases such as malaria.

What is the group of “tetracyclines”?

The group of ” tetracyclines ” constitutes a family of both natural and semisynthetic products, which have a special activity to prevent microbial or microbacterial activity , thanks to the formation of a naphthalene ring and its “tetracyclic” nucleus, where it derives its Name.

The most curious thing about this complex group of compounds is that they come from a bacterium belonging to the order ” Actinomyces “. This group of antibiotics can be recognized if placed under the action of an ultraviolet light .

Their medical uses are very varied, since they have the ability to dissolve quickly in the digestive tract and therefore are absorbed much faster when they reach the small intestine, reaching their maximum concentration in the blood in a period of no more than 6 hours.

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The great advantage offered by this group of drugs is that the resistance of bacteria to these is very low , generally, these bacteria belong to the order of ” Plasmids” and are treated with drugs administered directly at the health center. .

How does doxycycline work?

The Doxycycline , inhibits synthesis of proteins absorbed by different microorganisms, so that paralyzes and prevents their multiplication and nutrition which causes the death of the bacteria . For this reason, it is recommended to eliminate large populations of bacteria or inhibit rapid reproduction.

This medicine not only works by eliminating the culture broths and colonies of bacteria, it also works as a mechanism for regulating inflammation and consequently disables the derivatives of fatty lipases that absorb the bacteria in the area where it is found.

Lately this drug is indicated for the control of severe and severe cases of acne; Unlike other medications, this is used for both cases of acne , that is, hormonal acne and acne vulgaris since it eliminates the rapid proliferation of the bacteria characteristic of this pathology.

How should doxycycline be administered?

The presentation of Doxycycline comes in capsules or coated tablets of slow release and in suspension or syrup for pediatric use, also with the same mechanism of action mentioned above.

Doxycycline is usually given every 12 hours, that is, 2 times a day. To ingest the tablets you should drink a glass of water and if you start to feel discomfort in the stomach you can take it with some food or milk.

Remember that by ingesting the medicine with some food, perhaps the absorption of the remedy is not done in a complete way , resulting in a slower mechanism of action than taking it with just water.

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You must take into account the recommendations of the treating doctor , about the indications to take the medicine, likewise, the professional should guide you on the adverse effects that this medicine contains. You must follow the steps and instructions indicated by the doctor, since the packaging or label on the back of the medicine instructions are very generalized.

Another way to ingest Doxycycline is to divide the tablet in half (only if it is very difficult to swallow whole). It is important to take special care when performing this action, since part of the tablet may be accidentally crushed, losing part of the active ingredient.

Effectiveness of Doxycycline

The effectiveness of Doxycycline is really good since it has the ability to eliminate the great variety of aerobic and anaerobic bacteria that cause chronic diseases or at risk of relapse, such as: pneumonia or canine or human ehrlichiosis .

Within the group of ” tetracyclines” , the most potent is Doxycycline for almost all bacteria, it also has the ability to inhibit bacteria in vitro , such as; the Staphylococcus aureus and coagulase negative and Meticilinos resistant character .

Rarely can cases of rejection or resistance to ” Doxycycline” be observed , but when they do occur, their origin lies directly in the biological condition of the person or in other circumstances, it can be acquired by excessive consumption of the drug.

Is there a difference between Doxycycline and other tetracyclines?

It is important to bear in mind that there is a difference, since Doxycycline among the tetracyclines group is the drug with the highest fat solubility. That is, the molecule will access more directly through the lipid membrane of infectious agents.

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What precautions or recommendations does doxycycline have?

  • The doctor should be informed before indicating this drug if you are allergic to its components and in the event of a suspected adverse effect, the doctor should indicate a series of tests to rule out any hypersensitivity.
  • You must take precautions with other types of drugs that may be being administered at the moment, in this way possible adverse reactions are prevented due to the presence of both active compounds in the body. The doses of the other medications may need to be changed .
  • All use of antacids, calcium supplements, iron products and laxatives containing Aluminum or Magnesium should be discontinued, because their components influence the reaction of Doxycycline being less effective .
  • If you are taking birth control pills, you should keep in mind that Doxycycline , can significantly lower the effect of the pill , for it is recommended to use dual protection or abstinence.
  • It is not recommended in children under 8 years of age unless necessary or ultimately. In children, Doxycycline can permanently stain teeth.
  • If you are going to use Doxycycline as a preventive measure for malaria, you can help the treatment by using mosquito nets, insect repellants and complete clothing that covers as much of the body as possible.

Side Effects of Doxycycline

The adverse effects that doxycycline can cause are very few since it is completely absorbed in the small intestine, the occurrences of diarrhea, nausea or vomiting are rare. However, among these side effects you can find symptoms that can be quite serious.

Among which we can highlight: hepatotoxicity , nausea, vomiting, anorexia and inflammatory lesions in the intestinal or digestive tract. All these symptoms can be caused by its oral consumption as well as through intramuscular administration.

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Regarding the dermatological area, it can cause some reactions that directly affect the skin such as: dermatitis, maculopapular and erythematous eruptions and exfoliative dermatitis. Photosensitivity was recently discussed by the medical and pharmaceutical community.

Interaction with other medications

Currently it has been shown that drugs belonging to ” tetracycline” decrease the activity of prothrombin in plasma, which is why patients who consume anticoagulants will require a lower dose , this in order to avoid the clash between active principles.

In addition, it is recommended not to ingest it together with penicillin since the antibacterial action of Doxycycline cancels the effects of Penicillin . This happens because Penicillin originates from bacteria. 

At the same time, if you use ointments indicated for some type of skin burns and Doxycycline is administered together , you should avoid exposing to sunlight as much as possible because it can cause photosensitivity and complication in the affected area.

Doxycycline and the interaction with medicinal plants

If you are used to ingesting herbal tea, you should be especially careful if you are taking Doxycycline at the same time , as it increases the risk of being affected by the drug and decreases its effectiveness in the body; due to an antagonistic action against the plant compounds and the drug.

The most common adverse effects that occur are directly related to the absorption, distribution and excretion of the drug, thus preventing the drug from having a rapid speed of action.

The main problem occurs due to the laxative and diuretic properties that some plants possess , which causes the Doxycycline to be expelled in a faster and more disorderly way. They can also change the pH of the digestive system, thus creating compounds that are not absorbable.

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Another point to consider is that they can divert the action of the drug in the blood to another point that is not expected or indicated, developing an addictive effect for the person, between the plant and the drug.

Special cases where doxycycline can be used

Now we will see in detail what are the special cases where Doxycycline can be used.


Doxycycline can be used in emergencies due to anthrax as a preventive method, in such a way as to avoid the spread of malignant anthrax or anthrax, which can lead to death.

It is said that the use of this drug is preventive because if an emergency of this type occurs, the authorized health agents who arrive in the area do not know precisely who has inhaled the anthrax, so doxycycline doses are met until It is determined through pertinent examinations who should continue the treatment.

The dose to which people who have inhaled or have been in the risk zone should be subjected is to take the medicine twice a day for a minimum of 60 days . Health personnel will give people at risk the dose corresponding to the first ten days after exposure to anthrax.

After the ten days have elapsed, it will be determined which group of people it is necessary to continue taking the medicine and how to get it, in addition to carrying out a strict monitoring of all cases.

Anthrax is a highly dangerous and very serious disease that can be lethal and its form of contagion is the inhalation of the bacteria of the same name that cause the disease.

They should be taken into account with a higher risk of having contracted the disease by inhalation of bacteria, in cases where it occurs: fever, chills, exhaustion or fatigue, headache and recurrent cough.

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These are the symptoms with which the disease can begin to manifest itself, a picture that rapidly worsens and produces marked respiratory distress, affecting the central nervous system causing confusion and nausea at the gastrointestinal level.

These symptoms can appear after seven days of exposure to anthrax or immediately in a very aggressive way, so it is recommended that, when any of the symptoms described above appear, you go to a doctor immediately.


The Food and Drug Administration or FDA approves the use of Doxycycline as a preventive method for emergencies with anthrax, and the confidence in the benefits that can be obtained from the drug is such that the drug can still be used When the expiration date has passed, this would not be a problem because the drug would exert its action.


The answer to this question is a resounding NO , because the risks are also serious and can lead to death. Therefore, the risk is greater than just suspicions of having inhaled the bacteria that cause anthrax.

That is why it is recommended to look for alternatives in other available medications that can be used as prevention in an emergency situation, such as the danger of anthrax.


In cases of children, they must weigh more than 76 pounds or 35 kilos and adults over 18 years of age must take a 100 mg doxycycline pill twice a day together or not with food or milk. Its absorption will not be significantly affected so it does not matter if dairy is consumed.

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If the tablets can not be swallowed, they can be chewed or crushed and diluted in a small portion of water and then swallowed without any inconvenience.

In children weighing less than the one described above, the dose is adjusted according to weight and both the liquid form of doxycycline and the tablet may be crushed or chewed. Two daily intakes should also be taken at twelve-hour intervals, every day for the time prescribed by the doctor.


Treatment should be continued even if symptoms such as nausea, vomiting, diarrhea, sensitivity to the sun with the presence of a mild or moderate burn are present, as well as if there is a yeast infection. Only such conditions should be informed to the doctor and in case of aggravation, the actions to be followed will be determined.

If the throat closes or a very marked difficulty in breathing , edema of the face, tongue and lips, redness of the skin and hives, stomach cramps, presence of liquid diarrhea with blood, fever, changes in skin color turning yellow with repercussions on the liver and bile due to the presence of dark or brown urine.

Presence of bruises without explanation or apparent reason, vision failures, headaches, among others , can cause the total suspension of taking the medicine.


A doctor should be consulted in cases where the person takes anticoagulants, anticonvulsants, oral contraceptives , since doxycycline interferes with the action of these medications, so their effectiveness decreases.

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In cases where vitamins or antacids are being taken that contain calcium, zinc or magnesium in their composition: doxycycline doses must be adjusted since an antagonistic effect occurs in the antibiotic as a result of the interaction with these drugs.


Osteoarthritis is a disease that directly affects the bones, causing deformations as a result of inflammation in the joints of the bone system, especially the joints with greater impact and are responsible for supporting the body, such as: the hip and knee joints , mainly.

There is a loss of cartilage in the joint, so the organism in its compensation system produces bone growth to fill that space and repairs the damage, but it is a situation that once implanted does not help to improve what it does. cause more discomfort and pain.


According to studies carried out, it has been scientifically proven that doxycycline can block the damage to the joints caused by the presence of this type of degenerative joint diseases such as arthritis.

In turn, it reduces inflammation due to its anti-inflammatory effect . For this reason, it is a good option to use it during this process to obtain pain relief and not lose mobility or function of the joint.

Doxycycline should only be taken in tablet form for the time established by the treating physician, strictly following the indications to obtain good results.


In 2017, the results of a study carried out in the journal Scientific Reports , which belongs to the “Nature” group, was published by Agencia FAPESP / Karina Toledo that Doxycycline can be used at low doses in the treatment and improvement of Parkinson’s.

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Parkinson’s is a disease that occurs in the Central Nervous System as a degenerative process that affects or leads to death to dopaminergic neurons, which generates noticeable reactions at the body level such as: tremors, slowness of voluntary movements, rigidity, lack of of facial expression and other characteristic signs of this affectation.

During the study it was determined that Doxycycline acts by reducing the toxicity of a protein called α-synuclein that covers (through aggregates) and affects the functioning of the cells of the Central Nervous System in conditions such as Parkinson’s.

Until today it has not been tested in humans, but the results obtained in mice are encouraging; It is hoped that this neuroprotective effect of doxycycline in patients suffering from Parkinson’s disease can soon be used and stopped.

The discovery of this scientific advance was made by chance , although therapeutic alternatives were being studied before Parkinson’s, by Mauricio Lazzarini and a former graduate student at the Max Planck Institute of Experimental Medicine, in Germany more than five years ago.

At that time, they needed to subject experimental mice to states where this disease was present (Parkinson’s), they selected forty mice and administered a neurotoxic one that causes the death of dopaminergic neurons, such as 6-hydroxydopamine (6-OHDA) .

During the study, only two mice developed the disease, this caused great controversy and the possible causes for this event to occur were investigated. It was at that moment that a laboratory technician noticed that the feed with which the mice had been fed contained a small dose of Doxycycline.

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For this reason, the investigation of the hypothesis carried out on the possible substance that could have caused this protective effect of dopaminergic neurons in mice is started.

To verify the results, the experiment had to be repeated, but this time, using Doxycycline in two different presentations, a group of mice received it in food as powder, and the other group of mice received parenteral injections into the peritoneum of the same. medication and low doses.

The result was amazing, a total success in both presentations of the drug, so in 2013 the result was published in the journal Glia, explaining the benefits at the neuronal level in low doses, producing a protective and anti-inflammatory effect of dopaminergic neurons. of the Central Nervous System.

At present, research by recognized scientists continues, trying to achieve the same results in terms of protection of dopaminergic neurons through Doxycycline in human cells.

The results of the study in human cells have not yet been published, so it is estimated that they will soon give answers on how to improve the conditions of these patients suffering from Parkinson’s, with the action of low doses of Doxycycline.

The results in animals are surprising , this represents a great advance for science and medicine, as well as a great benefit not only for patients who suffer or are prone to the onset of Parkinson’s, but also, in patients who develop other degenerative pathologies of the Central Nervous System.

By only acting on the Central Nervous System Doxycycline decreasing the release of cytoxins and aggregates such as α-synuclein can protect not only dopaminergic neurons, but also other cells such as astocytes and the rest of Glia cells, so it would stop diseases such as Lewy body dementia that go hand in hand with Parkinson’s.

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Sexually Transmitted Diseases (STIs)

Regarding sexually transmitted diseases (STIs) and the effects of Doxycycline, we can see them right away.


If taken within the first 72 hours after exposure or sexual activity not protected by any barrier contraceptive method, sexually transmitted infections can be prevented.

Due to the high worldwide incidence of STIs, according to studies carried out, despite pre-exposure prophylaxis, there has been a need to investigate new methods that allow greater protection.

Therefore, the study of Doxycycline begins, as it has great results in Lyme disease and Leptospirosis . A sub-study of a randomized clinical trial called ANRS IPERGAY is carried out, with the use of Doxycycline, testing its effectiveness.

The study had a total of 232 HIV negative men (transgender women) with men 18 years of age or older, having sex, the population chosen for the study was the one at risk.

The results were variable according to the type of sexually transmitted disease faced during the study, so it is estimated that there was a significant reduction of 70% in cases of chlamydia infection.

In the case of Syphilis, there was a 73% reduction in risk for this disease, this result exceeds expectations regarding the prophylaxis obtained by the drug against STIs.

In this case, we can conclude, given such a result, that there must be an incorporation of this drug that, by making a synergism with other drugs, can reduce the high incidence of sexually transmitted diseases at present, in susceptible users of the population.

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Kathie Sand always saw the world of beauty as the terrain on which to build her professional career, a goal that was clear to her when she was only 15 years old. Her great concern to expand knowledge led her to settle in Paris where she studied hand in hand with the best beauty professionals and with the most advanced techniques for skin care.

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