An experiment on healthy young adults found that a single 200 mg oral dose of the antibiotic doxycycline slightly improved declarative learning and memory consolidation. It also very slightly reduced motor learning while improving long-term motor memory. The paper was published in European Neuropsychopharmacology.
Doxycycline is a broad-spectrum antibiotic in the tetracycline class, commonly used to treat bacterial infections. It is effective against a wide range of conditions, including respiratory tract infections, skin infections, sexually transmitted diseases, and certain types of acne.
Doxycycline is also used to treat and prevent malaria, as well as infections caused by tick-borne diseases such as Lyme disease and Rocky Mountain spotted fever. It works by inhibiting bacterial protein synthesis, thereby preventing the growth and spread of bacteria. This medication is usually taken orally and is generally well-tolerated, though it can cause side effects such as nausea, photosensitivity, and gastrointestinal discomfort.
More recently, tetracyclines like doxycycline and minocycline have been studied for their potential neuroprotective effects as treatments for neurodegenerative diseases, including Alzheimer’s disease, multiple sclerosis, and Parkinson’s disease. Neurodegenerative diseases are characterized by the gradual loss of neuronal function or death, which ultimately results in cognitive decline.
Study author Jelena M. Wehrli and her colleagues sought to explore whether a single oral dose of doxycycline negatively affects declarative memory consolidation. Declarative memory is a type of long-term memory that involves the conscious recall of facts, events, and knowledge, such as remembering names, dates, or specific experiences. The researchers reanalyzed data from three experiments investigating the effects of doxycycline on fear memory consolidation and reconsolidation.
The study participants, whose data came from the three experiments, were 261 healthy young adults recruited from the general population. They were all fluent in German and aged between 18 and 40 years, with a mean age of approximately 24 years.
Participants were randomly assigned to receive either a dose of doxycycline (Vibramycin®, 200 mg) or an identical placebo (mannitol). They were not informed whether they received doxycycline or the placebo. The 200 mg dose is the smallest amount recommended by the manufacturer. The participants completed three study visits in total, though the data analyzed in this study came from only two of these visits.
On the day of the treatment, participants first took their assigned capsule. Three-and-a-half to four-and-a-half hours later, they completed a series of neuropsychological tests, including tests of declarative verbal and visual memory, procedural motor skill learning, and sustained attention. Seven days later, during another study visit, their delayed recall of the materials learned during the earlier cognitive test battery was assessed.
The results showed no detrimental effects of doxycycline on declarative memory. Instead, a single dose of doxycycline slightly improved declarative learning and memory consolidation. The treatment very slightly reduced motor learning but subtly strengthened long-term motor memory.
“These results suggest that doxycycline can improve declarative learning and memory without having long term negative effects on other cognitive domains in healthy humans. Our results give hope to further investigate doxycycline in neuroprotective treatment applications,” the study authors concluded.
The study contributes to the scientific understanding of doxycycline’s effects on cognitive performance in healthy young adults. However, the observed effects were very weak and were noted only in the context of cognitive tests. Additionally, the participants were young individuals; the effects on older populations might differ.
The paper, “Forget me not: The effect of doxycycline on human declarative memory,” was authored by Jelena M Wehrli, Yanfang Xia, Laura Meister, Sarrina Tursunova, Birgit Kleim, Dominik R Bach, and Boris B Quednow.