Delays, therapeutic drug monitoring

Hydroxychloroquine lacks the myelosuppressive, hepatic, and renal tox-icities seen with some other DMARDs, which simplifies monitoring. Its onset may be delayed for up to 6 weeks, but the drug should not be considered a therapeutic failure until after 6 months of therapy with no... 

Increase the dosage by 5 to 10 mg/kg/wk to achieve optimal clinical response. Ordinarily, optimal clinical response is achieved at daily doses less than 60 mg/kg/day. If satisfactory clinical response has not been achieved, measure plasma levels to determine whether they are in the usually accepted therapeutic range (50 to 100 mcg/mL). Concomitant antiepilepsy drug (AED) dosage ordinarily can be reduced by about 25% every 2 weeks. This reduction may be started at initiation of therapy or delayed by 1 to 2 weeks if there is a concern that seizures are likely to occur. Monitor patients closely during this period for increased seizure frequency. 

For most antimicrobial agents, the relation between dose and therapeutic outcome is well established, and serum concentration monitoring is unnecessary for these drugs. To justify routine serum concentration monitoring, it should be established (1) that a direct relationship exists between drug concentrations and efficacy or toxicity (2) that substantial interpatient variability exists in serum concentrations on standard doses (3) that a small difference exists between therapeutic and toxic serum concentrations (4) that the clinical efficacy or toxicity of the drug is delayed or difficult to measure and (5) that an accurate assay is available. 

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