Identification and determination of the two principal metabolites of minocycline in humans

Tetracyclines and bone: Unclear actions with potentially lasting effects

Tetracyclines are a broad-spectrum class of antibiotics that have unclear actions with potentially lasting effects on bone metabolism. Initially isolated from Streptomyces, tetracycline proved to be an effective treatment for Gram +/- infections. The emergence of resistant bacterial strains commanded the development of later generation agents, including minocycline, doxycycline, tigecycline, sarecycline, omadacycline, and eravacycline. In 1957, it was realized that tetracyclines act as bone fluorochrome labels due to their high affinity for the bone mineral matrix. Over the course of the next decade, researchers discerned that these compounds are retained in the bone matrix at high levels after the termination of antibiotic therapy. Studies during this period provided evidence that tetracyclines could disrupt prenatal and early postnatal skeletal development. Currently, tetracyclines are most commonly prescribed as a long-term systemic therapy for the treatment of acne in healthy adolescents and young adults. Surprisingly, the impact of tetracyclines on physiologic bone modeling/remodeling is largely unknown. This article provides an overview of the pharmacology of tetracycline drugs, summarizes current knowledge about the impact of these agents on skeletal development and homeostasis, and reviews prior work targeting tetracyclines' effects on bone cell physiology. The need for future research to elucidate unclear effects of tetracyclines on the skeleton is addressed, including drug retention/release mechanisms from the bone matrix, signaling mechanisms at bone cells, the impact of newer third generation tetracycline antibiotics, and the role of the gut-bone axis.

Application of carbamyl in structural optimization

Carbamyl is considered a privileged structure in medicinal chemistry. It has a wide range of biological activities such as antimicrobial, anticancer, anti-epilepsy, for which the best evidence is a number of marketed carbamyl-containing drugs. Carbamyl is formed of primary amine and carbonyl moieties that act as hydrogen bond donors and hydrogen acceptors with residues of targets respectively, which are benefit for improving pharmacological activities. In other cases, the introduced carbamyl improves drug-like properties including oral bioavailability. In this review, we introduce the carbamyl-containing drugs and the application of carbamyl in structural optimization as a result of enhancing activities or/and drug-like properties.

Chronic oral administration of minocycline to sheep with ovine CLN6 neuronal ceroid lipofuscinosis maintains pharmacological concentrations in the brain but does not suppress neuroinflammation or disease progression

BACKGROUND

The neuronal ceroid lipofuscinoses (NCLs; or Batten disease) are fatal inherited human neurodegenerative diseases affecting an estimated 1:12,500 live births worldwide. They are caused by mutations in at least 11 different genes. Currently, there are no effective treatments. Progress into understanding pathogenesis and possible therapies depends on studying animal models. The most studied animals are the CLN6 South Hampshire sheep, in which the course of neuropathology closely follows that in affected children. Neurodegeneration, a hallmark of the disease, has been linked to neuroinflammation and is consequent to it. Activation of astrocytes and microglia begins prenatally, starting from specific foci associated with the later development of progressive cortical atrophy and the development of clinical symptoms, including the occipital cortex and blindness. Both neurodegeneration and neuroinflammation generalize and become more severe with increasing age and increasing clinical severity. The purpose of this study was to determine if chronic administration of an anti-inflammatory drug, minocycline, from an early age would halt or reverse the development of disease.

METHOD

Minocycline, a tetracycline family antibiotic with activity against neuroinflammation, was tested by chronic oral administration of 25 mg minocycline/kg/day to presymptomatic lambs affected with CLN6 NCL at 3 months of age to 14 months of age, when clinical symptoms are obvious, to determine if this would suppress neuroinflammation or disease progression.

RESULTS

Minocycline was absorbed without significant rumen biotransformation to maintain pharmacological concentrations of 1 μM in plasma and 400 nM in cerebrospinal fluid, but these did not result in inhibition of microglial activation or astrocytosis and did not change the neuronal loss or clinical course of the disease.

CONCLUSION

Oral administration is an effective route for drug delivery to the central nervous system in large animals, and model studies in these animals should precede highly speculative procedures in humans. Minocycline does not inhibit a critical step in the neuroinflammatory cascade in this form of Batten disease. Identification of the critical steps in the neuroinflammatory cascade in neurodegenerative diseases, and targeting of specific drugs to them, will greatly increase the likelihood of success.

Analysis of a second-generation tetracycline antibiotic minocycline in human plasma by LC-MS/MS

A simple, selective and sensitive LC-MS/MS assay has been developed for the determination of minocycline in human plasma. Plasma samples were prepared by protein precipitation, followed by chromatographic separation on a HyPURITY™ C8 (100 mm × 4.6 mm, 5 µm) column under isocratic conditions. The LOD and LLOQ of the method were 0.50 and 20.0 ng/ml, respectively. The intra-batch and inter-batch precision (% coefficient of variation) across quality control levels was less than 8.0%. For a set of incurred samples the percentage change in concentration was within ± 9.0%. The method was successfully applied to a bioequivalence study of 135 mg minocycline tablet formulation in 14 healthy Indian males. The reproducibility in the measurement of study data was demonstrated by incurred sample reanalysis.

Minocycline: a neuroprotective agent for hypoxic-ischemic brain injury in the neonate?

Minocycline is a second-generation tetracycline and a potential neuroprotective intervention following brain injury. However, despite the recognized beneficial effects of minocycline in a multitude of adult disease states, the clinical application of minocycline in neonates is contentious. Tetracyclines, as a class, are not usually administered to neonates, but there is compelling evidence that minocycline reduces brain injury after neonatal hypoxic-ischemic brain injury. This Review focuses on the evidence for minocycline use in neonates by considering aspects of pharmacology, drug regimens, functional outcomes, and mechanisms of action.

Metabolism, excretion, and pharmacokinetics of [14C]tigecycline, a first-in-class glycylcycline antibiotic, after intravenous infusion to healthy male subjects

Tigecycline, a novel, first-in-class glycylcycline antibiotic, has been approved for the treatment of complicated intra-abdominal infections and complicated skin and skin structure infections. The pharmacokinetics, metabolism, and excretion of [(14)C]tigecycline were examined in healthy male volunteers. Tigecycline has been shown to bind to bone; thus, to minimize the amount of radioactivity binding to bone and to maximize the recovery of radioactivity, tigecycline was administered intravenously (30-min infusion) as a single 100-mg dose, followed by six 50-mg doses, every 12 h, with the last dose being [(14)C]tigecycline (50 microCi). After the final dose, the pharmacokinetics of tigecycline in serum showed a long half-life (55.8 h) and a large volume of distribution (21.0 l/kg), whereas radioactivity in serum had a shorter half-life (6.9 h) and a smaller volume of distribution (3.3 l/kg). The major route of elimination was feces, containing 59% of the radioactive dose, whereas urine contained 32%. Unchanged tigecycline was the predominant drug-related compound in serum, urine, and feces. The major metabolic pathways identified were glucuronidation of tigecycline and amide hydrolysis followed by N-acetylation to form N-acetyl-9-aminominocycline. The glucuronide metabolites accounted for 5 to 20% of serum radioactivity, and approximately 9% of the dose was excreted as glucuronide conjugates within 48 h. Concentrations of N-acetyl-9-aminominocycline were approximately 6.5% and 11% of the tigecycline concentrations in serum and urine, respectively. Excretion of unchanged tigecycline into feces was the primary route of elimination, and the secondary elimination pathways were renal excretion of unchanged drug and metabolism to glucuronide conjugates and N-acetyl-9-aminominocycline.

Correlação entre dose/concentração plasmática e avaliação de alterações hepáticas e renais em ratos Wistar tratados com o esquema ROM

A hanseníase, doença crônica, granulomatosa, infecto-contagiosa, transmitida pelo Mycobacterium leprae, ainda se mantém prevalente nos dias atuais, principalmente em países subdesenvolvidos e a sua forma paucibacilar com lesão única, vem sendo tratada através da administração de rifampicina (600mg), ofloxacina (400mg) e minociclina (100mg), em dose única (esquema ROM). Assim, o objetivo deste trabalho foi investigar a correlação dose/concentração plasmática versus alterações bioquímicas na administração da rifampicina, ofloxacina e minociclina a ratos machos Wistar, em regime de dose única em mono e politerapia. Concluímos que a rifampicina e a ofloxacina sofreram um aumento na concentração plasmática quando administrados em politerapia, enquanto que a minociclina sofreu uma redução, provavelmente por interferências na biotransformação e excreção. Constatamos através das análises bioquímicas que a rifampicina provavelmente é a responsável por alterações hepáticas e renais, e que as interações medicamentosas envolvendo o fármaco exigem estudos individualizados principalmente quando o fármaco é usado associado a ofloxacina e minociclina.

Determination of minocycline in human plasma by high-performance liquid chromatography coupled to tandem mass spectrometry: application to bioequivalence study

Minocycline was determined in human plasma by HPLC-MS-MS using clarithromycin as an internal standard. The method is fast (single liquid extraction and run time of <3 min) and sensitive (5 ng/ml) and it was employed in a bioequivalence study of two 100 mg tablet formulations in 24 healthy volunteers. The 90% confidence interval of the individual ratio geometric mean for both AUC(0-96 h) and Cmax were 99.2-111.1% and 95.6-117.5%, respectively. Thus, Minoderm was considered bioequivalent to Minomax according to both the rate and extent of absorption. No food interaction was observed with either formulation.

Chromatographic analysis of tetracycline antibiotics in foods

Tetracycline antibiotics (TCs), such as oxytetracycline, tetracycline, chlortetracycline, and doxycycline, have for decades continued to play an important role in veterinary medicine and feed additives because of the broad spectrum antibiotics and their economical advantages. Many analysis methods of TCs, therefore, have been reported to monitor their residues in foods. We review the recent developments in chromatographic analysis methods for TCs in foods. This review involves the following techniques: thin layer chromatography, capillary electrophoresis, high-performance liquid chromatography, and sample preparation including extraction and clean up procedures.

High-performance liquid chromatographic assay for minocycline in human plasma and parotid saliva

A sensitive and specific high-performance liquid chromatographic (HPLC) method with UV detection was developed for the determination of minocycline in human plasma and parotid saliva samples. Samples were extracted using an Oasis HLB cartridge and were injected into a C8 Nucleosil column. The HPLC eluent contained acetonitrile-methanol-distilled water-0.1% trifluoroacetic acid (25:2:72.9:0.1, v/v). Demeclocycline was used as internal standard. The assay showed linearity in the tested range of 0.1-25 microg/ml. The limit of quantitation was 100 ng/ml. Recovery from plasma or parotid saliva averaged 95%. Precision expressed as %CV was in the range 0.2-17% (limit of quantitation). Accuracy ranged from 93 to 111%. In the two matrices studied at 20 and 4 degrees C, rapid degradation of the drug occurred. Frozen at -30 degrees C, this drug was stable for at least 2 months, the percent recovery averaged 90%. The method's ability to quantify minocycline with precision, accuracy and sensitivity makes it useful in pharmacokinetic studies.

Determination of minocycline in human plasma by high-performance liquid chromatography with UV detection after liquid-liquid extraction

A sensitive and specific high-performance liquid chromatographic method was developed and validated for the determination of minocycline in human plasma. The method uses liquid-liquid extraction, reextraction and HPLC with UV detection. The assay shows linearity in the tested range of 28-3533 ng/ml with a limit of quantification of 30 ng/ml. The inter-day precision was found to be +/-3.84 to +/-6.57% (R.S.D.) in the range of 148 to 2743 ng/ml. The method was successfully applied to pharmacokinetic studies.