In "double tetracycline labeling", a second dose is given 11–14 days after the first dose, and the amount of bone formed during that interval can be calculated by measuring the distance between the two fluorescent labels.Tetracycline is also used as a biomarker in wildlife to detect consumption of medicine- or vaccine-containing baits. Side effects
Use of tetracycline antibiotics can:
Discolor permanent teeth (yellow-gray-brown), from prenatal period through childhood and adulthood. Children receiving long- or short-term therapy with a tetracycline or glycylcycline may develop permanent brown discoloration of the teeth. Be inactivated by calcium ions, so are not to be taken with milk, yogurt, and other dairy products
Be inactivated by aluminium, iron, and zinc ions, not to be taken at the same time as indigestion remedies (some common antacids and over-the-counter heartburn medicines)
Cause skin photosensitivity, so exposure to the sun or intense light is not recommended
Cause drug-induced lupus, and hepatitis
Cause microvesicular fatty liver
Cause tinnitus
Interfere with methotrexate by displacing it from the various protein-binding sites
Cause breathing complications, as well as anaphylactic shock, in some individuals
Affect bone growth of the fetus, so should be avoided during pregnancy
Fanconi syndrome may result from ingesting expired tetracyclines.Caution should be exercised in long-term use when breastfeeding. Short-term use is safe; bioavailability in milk is low to nil. According to the U.S. Food and Drug Administration (FDA),  cases of Stevens–Johnson syndrome, toxic epidermal necrolysis, and erythema multiforme associated with doxycycline use have been reported, but a causative role has not been established.
This was similar to an SMD of 0.26 for olanzapine/fluoxetine for TRD and lower than SMDs of 0.35 for aripiprazole and 0.40 for quetiapine as adjuncts for MDD. These drugs are less expensive than esketamine and may serve as more affordable alternatives to it for depression with similar effectiveness. Adverse effects
The most common adverse effects of esketamine for depression (≥5% incidence) include dissociation, dizziness, sedation, nausea, vomiting, vertigo, numbness, anxiety, lethargy, increased blood pressure, and feelings of drunkenness. Long-term use of esketamine has been associated with bladder disease. Pharmacology
Pharmacodynamics
Esketamine is approximately twice as potent an anesthetic as racemic ketamine.In mice, the rapid antidepressant effect of arketamine was greater and lasted longer than that of esketamine. The usefulness of arketamine over esketamine has been supported by other researchers.Esketamine inhibits dopamine transporters eight times more than arketamine. This increases dopamine activity in the brain. At doses causing the same intensity of effects, esketamine is generally considered to be more pleasant by patients. Patients also generally recover mental function more quickly after being treated with pure esketamine, which may be a result of the fact that it is cleared from their system more quickly. This is however in contradiction with arketamine being devoid of psychotomimetic side effects.Unlike arketamine, esketamine does not bind significantly to sigma receptors. Esketamine increases glucose metabolism in the frontal cortex, while arketamine decreases glucose metabolism in the brain. This difference may be responsible for the fact that esketamine generally has a more dissociative or hallucinogenic effect while arketamine is reportedly more relaxing.