The FDA recently cleared the AmpliChip CYP450 Test (Roche), which analyzes blood-derived DNA to detect genetic variations in the activity of cytochrome P450 (CYP) enzymes CYP2D6 and CYP2C19 and determines the metabolizer status of the patient. The test is intended to help guide clinicians in prescribing individualized drug therapy. About 25% of all drugs, including many antidepressants and antipsychotics, are substrates of either CYP2D6 or CYP2C19. The test is being promoted initially to psychiatrists.

Consensi (Coeptis/Burke), a fixed-dose combination of the calcium channel blocker amlodipine (Norvasc, and others) and the COX-2 selective NSAID celecoxib (Celebrex, and generics), has been approved by the FDA for treatment of patients who have hypertension and osteoarthritis.

Changes caused by one drug in the absorption, distribution, metabolism or excretion of another may lead to a pharmacokinetic adverse drug interaction (DN Juurlink et al, JAMA 2003; 289:1652). Additive drug interactions, such as vasodilation caused by both sildenafil (Viagra) and nitrates, can also have adverse effects.

The ability of grapefruit juice to increase serum concentrations of drugs was first discovered during a study of the effect of ethanol on felodipine (Plendil) pharmacokinetics. Double-strength grapefruit juice used to disguise the taste of ethanol resulted in higher than expected serum concentrations of felodipine (DG Bailey et al, Clin Invest Med 1989; 12:357).

In 2013 the FDA approved one new drug and a new combination of 2 old drugs as adjuncts to lifestyle changes for chronic weight management. Lorcaserin (lor-ca-SER-in; Belviq – Arena/Esai) is a selective serotonin 2C receptor agonist. Qsymia (Vivus) is a fixed-dose combination of the weight-loss drug phentermine and an extended-release (ER) formulation of topiramate. The new products are approved for use in obese patients (body mass index [BMI] of ≥30 kg/m2) and for patients who are overweight (BMI ≥27 kg/m2) and have one weight-related risk factor such as hypertension, dyslipidemia or...

An oral solution (Vituz – Hawthorne) containing two old drugs, the centrally-acting opioid hydrocodone bitartrate and the first-generation H1-antihistamine chlorpheniramine maleate, has been approved by the FDA for relief of cough and [other] symptoms associated with upper respiratory allergies or a common cold in adults. Several extended-release products containing hydrocodone and chlorpheniramine are available as capsules and suspensions and have been used for years for similar indications. Vituz is classified as a schedule III controlled substance, but the FDA has asked the DEA...

The FDA has approved vemurafenib (Zelboraf – Genentech), a kinase inhibitor, for treatment of unresectable or metastatic melanoma with the BRAF V600E mutation, which is found in 30-60% of melanomas. An FDA-approved test can detect the mutation in DNA from melanoma tissue.

Alzheimer's disease (AD) is the most common cause of dementia, but cognitive decline is also associated with other neurological conditions such as Parkinson's disease, dementia with Lewy bodies, vascular dementia, and frontotemporal dementia.

Many drugs can cause psychiatric symptoms, but a causal connection is often difficult to establish. Psychiatric symptoms that emerge during drug treatment could also be due to the underlying illness, previously unrecognized psychopathology, or psychosocial factors. The withdrawal of some drugs can cause symptoms such as anxiety, psychosis, delirium, agitation or depression.

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Testing for drug use has become increasingly common, not only in health care, but also in drug rehabilitation, in the military, at the workplace, after accidents and in the criminal justice system. Performance-enhancing drugs such as anabolic steroids, growth hormone (Genotropin, and others) and erythropoietin (Procrit, Epogen) are not discussed here.