Drug interactions
Allopurinol inhibits xanthine oxidase, the enzyme that breaks down mercaptopurine. Those taking allopurinol (often used to prevent gout) are at risk for mercaptopurine toxicity. The dose should be reduced or allopurinol should be discontinued. Several published studies have demonstrated that the use of allopurinol in combination with low dose 6-MP helps reduce 6-MP levels, which are toxic to liver tissue, whilst increasing the therapeutic levels of 6-MP for some inflammatory conditions. Mechanisms of action
Official information from the package insert for purinethol:
Mercaptopurine is an antimetabolite antineoplastic, as such it interferes with normal metabolic processes within cells, typically by combining with enzymes, to disrupt DNA and RNA synthesis (cell-cycle S phase-specific) leading to death of rapidly proliferating cells, especially malignant ones. Specifically, Mercaptopurine is a purine antimetabolite or purine antagonist as such inhibits DNA synthesis by inhibiting the production of the purine containing nucleotides, adenine and guanine thus halting DNA synthesis. Mercaptopurine also acts as an immunomodulator by inhibiting of several pathways in nucleic acid biosynthesis preventing proliferation of cells involved in the determination and amplification of the immune response. Mercaptopurine (6-MP) competes with the purine derivatives hypoxanthine and guanine for the enzyme HGPRT and is itself converted to thio inosine monophosphate (TIMP). TIMP inhibits several chemical reactions involving inosinic acid (IMP), including the conversion of IMP to xanthylic acid (XMP) and the conversion of IMP to adenylic acid (AMP) via adenylosuccinate (SAMP). In addition, 6-methylthioinosinate (MTIMP) is formed by the methylation of TIMP.
Respiratory illness
Heart defects (e.g., pulmonary stenosis, VSD, ASD, coarctation of the aorta)
Hearing impairment
Vision abnormalities (e.g., ptosis, nystagmus, high myopia, hypertropia)
Partial joining of the second and third toes
Incurved 5th fingers (clinodactyly)
Gastroesophageal reflux
Gastrointestinal abnormalities
Musculoskeletal problems
Scoliosis
Social anxiety
Seizures
Cleft palate
Feeding problemsChildren with this syndrome are often found to have long eyelashes, bushy eyebrows and synophrys (joined eyebrows). Body hair can be excessive and affected individuals are often shorter than their immediate family members. They present a characteristic facial phenotype.Children with CdLS often have gastrointestinal tract difficulties, particularly gastroesophageal reflux. Vomiting, intermittent poor appetite, constipation, diarrhea or gaseous distention are known to be a regularity in cases where the GI tract problems are acute. Symptoms may range from mild to severe. People with CdLS may exhibit behaviours that have been described as "autistic-like," including self-stimulation, aggression, self-injury or strong preference to a structured routine. Behavior problems in CdLS are not inevitable. Many behaviour issues associated with CdLS are reactive (i.e., something happens within the persons body or environment to bring on the behavior) and cyclical (comes and goes). Often, an underlying medical issue, pain, social anxiety, environmental or caregiver stress can be associated with a change behaviour. If pain or a medical issue is the cause, once treated, the behaviour diminishes. There is evidence for some features of premature aging including the early development of Barrett’s esophagus, osteoporosis present in the teenage years, premature greying of hair and some changes to the skin of the face causing a more aged appearance compared to chronological age.