Evaluation of therapeutic drug monitoring of methotrexate in saliva of children with rheumatic diseases

Saliva as a Future Field in Psoriasis Research

Psoriasis is a skin inflammatory disease characterized by an increased body of comorbidities, including parodontopathy. Despite the visibility of skin lesions, prognostic biomarkers, related to disease monitoring and therapeutic effectiveness, are still missing. Although several markers have been studied, none of them has been identified as an independent prognostic factor. This concise review aims to summarize the current knowledge and results in saliva research applied to psoriasis. Combination of different markers could improve the prognostic prediction in patients with psoriasis. Future studies are needed to implement research on salivary biomarkers and their prognostic/therapeutic effects in the management of patients with psoriasis.

A validated LC-MS/MS method for rapid determination of methotrexate in human saliva and its application to an excretion evaluation study

A sensitive and simple method for the methotrexate quantification was developed using aminopterin as internal standard. Methotrexate is an anticancer agent that is widely used in a variety of human cancers including primary central nervous system lymphoma. The compound was quantified by liquid-chromatography coupled to electrospray ionization (positive ion-mode) low-energy collision dissociation-tandem mass spectrometry. Quantitative detection was by multiple reaction monitoring of the transitions of the [M+H]+ ion of MTX to its common product ion at m/z 308.4 and of aminopterin at m/z 441.2→m/z 294.0. The method demonstrated linearity over at least three orders of magnitude and had a detection limit of 1ng/ml for methotrexate. A run time of less than 8.0min for each sample made it possible to analyze a large number of human saliva samples per day. Application of this procedure was demonstrated to a saliva excretion study of methotrexate on the samples obtained after an intravenously administration of 1mg/kg/dose of methotrexate to six patients with acute lymphoblastic leukemia.

Oral effects of low-dose methotrexate treatment

Methotrexate is used increasingly in low-dose regimes for a variety of conditions, particularly rheumatoid arthritis. While certain adverse effects of low-dose methotrexate have been described in detail, oral complications have received little attention. This article includes a summary of the uses and pharmacology of low-dose methotrexate and the mechanisms that lead to general and oral toxicity. The literature relevant to potential oral adverse effects is discussed and 7 illustrative cases are presented. The oral effects noted range from nonhealing ulcers to lymphoma-like lesions. Dental practitioners should be aware of the possible oral effects of low-dose methotrexate that have so far been largely unrecognized.

Review: The physiology of saliva and transfer of drugs into saliva

Although saliva or oral fluid "lacks the drama of blood, the sincerity of sweat and the emotional appeal of tears", quoting Mandel in 1990 [I.D. Mandel, The diagnostic uses of saliva, J. Oral Pathol. Med. 19 (1990) 119-125], it is now meeting the demand for inexpensive, non-invasive and easy-to-use diagnostic aids for oral and systemic diseases, drug monitoring and detection of illicit use of drugs of abuse, including alcohol. As the salivary secretion is a reflex response controlled by both parasympathetic and sympathetic secretomotor nerves, it can be influenced by several stimuli. Moreover, patients taking medication which influences either the central nervous system or the peripheral nervous system, or medication which mimic the latter as a side effect, will have an altered salivary composition and salivary volume. Patients suffering from certain systemic diseases may present the same salivary alterations. The circadian rhythm determines both the volume of saliva that will and can be secreted and the salivary electrolyte concentrations. Dietary influences and the patient's age also have an impact on composition and volume of saliva. The latter implies a wide variation in composition both inter- and intra-individually. Sampling must therefore be performed under standardized conditions. The greatest advantage, when compared to blood sample collection, is that saliva is readily accessible and collectible. Consequently, it can be used in clinically difficult situations, such as in children, handicapped and anxious patients, where blood sampling could be a difficult act to perform.

Clinical utility of free drug monitoring

Most drugs are bound to serum proteins to a various degree. Only unbound or free drug is pharmacologically active. Usually total drug is measured for therapeutic monitoring because there is equilibrium between bound and free drugs, and concentration of free drug can be predicted from total drug concentration. However, under certain conditions this equilibrium is disturbed and the measured free drug concentration can be significantly higher than expected from total drug concentrations, especially for strongly protein-bound drugs. In such case a patient may experience drug toxicity even if the total drug concentration is within the therapeutic range. Conditions like uremia, liver disease and hypoalbuminemia can lead to significant increases in free drug concentration. Therefore, monitoring free phenytoin and free valproic acid is recommended in these patients. Drug-drug interactions can also lead to a disproportionate increase in free drug concentration. One strongly protein-bound drug can significantly displace another strongly protein-bound drug if both drugs share the same binding site. Several over-the-counter pain medications such as salicylate, naproxen, and ibuprofen can cause significant displacement of both phenytoin and valproic acid from albumin binding site. Interestingly, such interactions are absent in uremic patients. Elderly patients may have increased free phenytoin or valproic acid due to hypoalbuminemia. Elevated free phenytoin concentrations have also been reported in patients with AIDS. Although digoxin is 25% bound to protein, monitoring free digoxin is useful in patients with elevated endogenous digoxin-like immunoreactive substances or in patients overdosed with digoxin and being treated with digibind. Monitoring free digoxin can also eliminate interference of Chinese medicines Chan Su and Danshen in serum digoxin measurement by certain immunoassays. However, free drug monitoring is not a routine procedure in clinical laboratories due to technical difficulties and lack of established reference ranges for free drugs.

Methotrexate in the treatment of juvenile rheumatoid arthritis and other pediatric rheumatoid and nonrheumatic disorders

The goal of treatment for juvenile rheumatoid arthritis (JRA) and other pediatric rheumatic disorders is to minimize joint destruction, pain, and deformity and to maximize all aspects of growth and development. Oral and injectable methotrexate are now often given early in the treatment of JRA, childhood dermatomyositis, difficult-to-control arthritis in the pediatric spondyloarthropathies, SLE, sarcoidosis, several of the vasculopathies, and idiopathic iritis. Weekly low-dose MTX has become a mainstay of long-term improved control of these disorders, and is associated with strikingly few documented long-term side effects. Dosages, pharmacology, side effects, efficacy, and treatment strategies are discussed. Although formal studies are lacking, MTX for the pediatric rheumatic disorders seems to be associated with less frequent physician visits, lower total costs, improved function, and fewer late reconstructive surgeries.

Salivary measurement of deferiprone concentrations and correlation with serum levels

Deferiprone (L1) is the first clinically available oral iron chelator and it has been proven to be effective for the treatment of transfusional iron overload in thalassemic patients. Because many of these patients have impaired compliance with their medications, effective means of continuous monitoring of compliance are crucial. Saliva drug monitoring has the potential advantage of an easy, noninvasive approach, assuming that it represents serum levels. However, drugs have variable correlations between saliva and serum concentration. We compared serum and saliva levels of L1 at various time points after ingestion of a 75 mg/kg/day dose in nine thalassemic patients. A highly significant correlation between serum-free L1 and saliva levels (r = 0.97, p = 0.0003) was found. Pharmacokinetic profiles were similar using serum and saliva monitoring. We conclude that saliva can be substituted for serum in monitoring L1 levels.

Noninvasive methods for drug measurement in pediatrics

Infants and children present a special challenge to drug monitoring because the disposition of drugs differs from adults and because there are far fewer clinical studies designed for children than for adults. The excuse for this unfortunate situation is the imposition of severe technical and ethical constraints caused by blood sampling; however, in the past two decades, several new noninvasive methods to measure drugs have been tested and implemented in therapeutic drug monitoring. It is our hope that these new techniques will help advance the ability to diagnose and manage infants and young children.