Valproic acid monitoring

A competitive fluorescence-polarization immunoassay method was described for the monitoring of 12 drugs including valproic acid [18]. Samples (serum or plasma) were deproteinated. Fluorescence from the fluorescein-labeled analyte used as tracer was excited at 488 nm and polarization of light emitted at 531 nm was measured. The calibration was stable for 4 weeks and the coefficient of variation was below 10%. A single measurement took 8-10 min. 

Of the mood stabilizers, valproic acid (Depakene, Depakote) is the most widely used. Like the other mood stabilizers, its onset of action can be delayed by several days. Valproic acid is a reasonably well tolerated mood stabilizer. It does occasionally cause tremor, and it can on rare occasion lower platelet counts or cause liver problems. For this reason, blood monitoring is required when starting this medication. In addition, valproic acid can irritate the stomach lining, but this problem is largely overcome by using the buffered form sodium divalproex (Depakote or Depakote ER). Finally, valproic acid can also cause hair loss or drowsiness. 

Unlike carbamazepine, valproic acid has few drug interactions, an added benefit for elderly patients. One interaction worthy of mention, however, is that aspirin can increase levels of valproic acid. For this reason, vascular dementia patients taking an aspirin a day may need a lower dose of valproic acid or at least more careful monitoring of blood levels when starting valproic acid. 

Carbamazepine is believed to be effective in BPD, though the data is far less robust than with valproic acid. It is prescribed at doses up to 1200mg/day. Like valproic acid, it can also canse birth defects and requires laboratory monitoring including serum levels. For more information on the use of carbamazepine, please refer to the discussion of bipolar disorder treatment in Chapter 3. 

Bismuth Subsalicylate (Pepto-Bismol) [Antidiarrheal/ Adsorbent] [OTC] Uses Indigestion, N, D combo for Rx of H. pylori Infxn Action Antisecretory anti-inflammatory E>o e Adults. 2 tabs or 30 mL PO PRN (max 8 doses/24 h) Feds. 3—6 y 1/3 tab or 5 mL PO PRN (max 8 doses/24 h) 5-9 y 2/3 tab or 10 mL PO PRN (max 8 doses/24 h) 9-72 y 1 tab or 15 mL PO PRN (max 8 doses/24 h) Caution [C, D (3rd tri), -] Avoid w/ renal failure Hx severe GI bleed Contra Influenza or chickenpox (T risk of Reye synd), ASA allergy (see Aspirin) Disp Chew tabs, caplets, Liq, susp SE May turn tongue stools black Interactions T Effects OF ASA, MTX, valproic acid effects OF tetracyclines i effects W/ corticosteroids, probenecid EMS Monitor for hypovolemia and electrolyte disturbances d/t D may darken tongue stool OD Similar to ASA OD V, tinnitus, metabolic acidosis activated charcoal may be effective... 

Vorinostat (Zolinza) [Histone Deacetylase Inhibitor] Uses Rx cutaneous manifestations in cutaneous T-cell lymphoma Action Histone deacetylase inhibitor Dose 400 mg PO daily w/ food if intolerant X 300 mg PO d for X 5 d each wk Caution [D /-] w/ warfarin (t INR) Disp Caps SE NA /D, dehydration, fatigue, anorexia, dysgeusia, DVT, PE, Xplt, anemia, hypoglycemia, QT prolongation Interactions t Risk of thrombocytopenia GI bleed W/HDAC inhibitors (valproic acid) EMS May t QT interval, monitor ECG may t glucose T risk of DVT has been r orted OD Sxs unknown... 

The Depakote form of valproic acid is approved for the acute phase of bipolar disorder. It is also commonly used on a long-term basis, although its prophylactic effects have not been as well established. Valproic acid is now frequently used as a first-line treatment for bipolar disorders, as well as in combination with lithium for patients refractory to lithium monotherapy and especially for patients with rapid cycling and mixed episodes. Oral loading can lead to rapid stabilization, and plasma levels must be monitored to keep drug levels within the therapeutic range. 

Serious drug interactions are uncommon with valproate. Approximately 25% of valproate metabolism is dependent on CYP isoenzymes. Valproic acid can cause severe liver damage during the first 6 months of treatment. Note interactions with aspirin and the need to monitor plasma free valproate levels. 

PLATINUM COMPOUNDS ANTIEPILEPTICS -CARBAMAZEPINE, PHENYTOIN, VALPROIC ACID l plasma concentrations of antiepileptic, which t risk of seizures Due to impaired absorption of antiepileptic Monitor closely for seizure activity and warn patients and carers. Need to adjust dosage using parameters such as blood levels to ensure therapeutic levels... 

Monitor valproic acid toxicity over time—if toxicity continues, consider decreasing dose... 

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