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Home » Laboratory Monitoring When Prescribing Psychotropics

Laboratory Monitoring When Prescribing Psychotropics

August 1, 2007
From The Carlat Psychiatry Report
Issue Links: Learning Objectives | Editorial Information | PDF of Issue
Daniel Carlat, MD

When you are planning to start a patient on medications, what labs should you order at baseline, and what should you order over time? This is quite a different question from whether to do a set of labs at the start of treatment to screen for disease etiology, and it’s an area where I believe we should be much more proactive.Note: Before you start any medication on a woman of child-bearing age, you should order a urine pregnancy test – just in case!

Antidepressants

Specific Serotonin Reuptake Inhibitors (SSRIs). No lab monitoring required. However, you may want to order the appropriate labs if patients experience any of these three recently reported medical complications of SSRIs.

1. Bleeding. Most commonly manifesting as GI bleeding (Meijer W. Arch Internal Medicine 2004;164:2367-2370), the bleeding risk of SSRIs is not thought to be caused by platelet dysfunction, but is probably a direct effect of serotonergic stimulation. This is such a rare side effect that routine monitoring of the hematocrit is not indicated, but order a CBC if a patient presents with symptoms suggestive of blood loss.

2. Hyponatremia. Significant SSRI-induced hyponatremia (below 130) is rare, and it is most likely to occur in patients over 65 within 30 days of starting the SSRI (Consult Pharm 2000;15:160-77. http://www.ascp.com/publications/tcp/2000/feb/cr_hypo.shtml). Again, it is too rare a side effect to merit routine Na monitoring, but consider ordering an electrolyte panel if an elderly patient recently started on SSRIs reports fatigue, dizziness, or cramping.

3. Osteoporosis. Two recent studies suggest that SSRI use decreases bone density in the elderly, placing them at greater risk for osteoporosis. The effect was not huge, but was large enough for the authors to recommend that elderly patients on SSRIs should have routine bone density screenings (see this month’s Research Updates for more details and references).

Effexor XR (venlafaxine XR). Patients should have their blood pressure checked periodically after starting or increasing the dose of Effexor XR. The risk of hypretension is dose-dependent, so monitoring should be more vigilant at doses of 225 mg or higher.

Cymbalta (duloxetine). Since Cymbalta causes elevation of alanine transaminase (ALT) in 1% of patients, check ALT at some point after the patient starts it.

Tricyclics. In patients with pre-existing cardiac disease, order an ECG both before starting a tricyclic and after reaching a therapeutic dose.  Some authorities recommend a screening ECG in any patient above 40 or 50, regardless of cardiac history. There is some evidence endorsing the value of monitoring the serum level of nortriptyline, with a therapeutic “window” of 50-150 ng/mL correlating with the best antidepressant results.

MAOIs. Phenelzine (Nardil) has been reported to cause liver failure in case reports (Gomez-Gil et al., Annals Internal Medicine 1996;124:692-693), so some clinicians recommend monitoring LFTs after starting it.

Antipsychotics
The importance of the metabolic syndrome has been pounded into our brains as a result of the marketing wars between the different makers of atypical antipsychotics. To review: Metabolic syndrome it is defined as a combination of abdominal obesity, elevated fasting plasma glucose levels, elevated triglyceride levels, low HDL cholesterol levels, and hypertension.

Several antipsychotics appear to cause the metabolic syndrome, though there is disagreement about which ones lead to significant risk. TCPR has had the displeasure of reviewing this very complicated literature in past issues, and based on this we divide up the commonly used antipsychotics into two categories: metabolically dirty vs. metabolically clean. Another good source of recommendations came from the Mt. Sinai group (Marder et al., Am J Psych 2004; 161:1334-1349).

Metabolically “dirty” antipsychotics include: Zyprexa (olanzapine), clozapine, Risperdal (risperidone), Seroquel (quetiapine), chlorpromazine, and thioridazine.

Metabolically “clean” (or at least cleaner) antipsychotics: Abilify (aripiprazole), Geodon (ziprasidone), haloperidol, Trilafon (perphenazine).

Here are our monitoring recommendations for these two different categories:

“Dirty” antipsychotics. Weight. Determine BMI (body mass index, defined as weight divided by height) at baseline, once a month for the first three months, then every three months. Glucose. 1. Baseline fasting glucose (below 100 is normal, 100-125 is pre-diabetes, above 126 is diabetes). If your patient can't manage to get to the lab before eating, order an HbA1c, which is a measure of long term glucose control.

2. Follow-up fasting glucose 4 months after starting med and then yearly, unless patients are gaining weight: if so, continue Q 4 mo. monitoring. Ask patients about polyuria or polydipsia to monitor for diabetes. Lipids. Baseline fasting lipid panel: total cholesterol, low-density lipoprotein (LDL) and HDL cholesterol, and triglyceride levels. Check lipids again 3 months later, then every 2 years; refer to PCP if LDL is higher than 130 mg/dl.

“Clean” antipsychotics. Weight. Baseline, 6 months, then yearly. Glucose. Baseline glucose (fasting not necessary); then yearly. Lipids. Baseline fasting lipid panel every 2 years.

ECG Monitoring
Mellaril (thioridazine), Serentil (mesoridazine, no longer available in U.S.), and Orap (pimozide) should not be prescribed for anyone with known heart disease. Geodon can be prescribed in patients with heart disease, but you should get a baseline ECG, and get follow-up ECG. In patients with no cardiac history, no screening ECG is required.

Prolactin
Patients on Risperdal and most first generation antipsychotics should be asked screening questions about symptoms of elevated prolactin. For women, ask about changes in menstruation or libido, and whether they have noticed a milk discharge from breasts. For men, ask about libido and sexual dysfunction. Order prolactin levels only if screening questions indicate possible hyperprolactinemia.

Mood Stabilizers
(See chart below)



General Comments: 1) In the ideal world, you would review baseline lab results before starting meds, but in the real world this is rarely feasible or necessary; 2) recommendations for one or two week follow-up labs are cautious, and many clinicians (including myself) will order such early follow-up labs only if there is a clinical clue of a lab abnormality.  

































































































Meds/Labs



Recommendations



Notes



Lithium  





Serum Level



 

 

After one week, then yearly or as indicated (dosage changes, clinical or compliance issues, or new side effects)



Li levels won’t change after they reach steady state levels, unless an outside factor intervenes



TSH



Baseline, two weeks, six months, then yearly



Thyroid issues typically arise 2 wks. to 6 mos. after starting Li



BUN/Creatinine



Baseline, two weeks, yearly






EKG



Not needed for most patients; those with cardiac history should receive cardiac follow-up with PCP



Small incidence of bradycardia due to sinus node dysfunction—requires more than an EKG for eval.



Depakote (valproic acid) 





  



Serum Level



After one week, then yearly or as indicated (dosage changes, clinical or compliance issues, or new side effects)



Depakote levels won’t change after they reach steady state levels, unless an outside factor intervenes



LFTs



Baseline, two weeks, then yearly, unless symptoms of hepatitis



Hepatotoxicity almost unheard of in patients over the age of 2; mild increased LFT’s more common, usually benign, reversible



CBC



After two weeks, then at six months, then yearly (unless easy bruisability)—more vigilance in elderly



Significant thrombocytopenia rare in large studies; elderly may be at more risk




Tegretol (carbamazepine)



   



Serum Level



At one week, one month, yearly (repeat with dosage changes, clinical or compliance issues, or new side effects)



Because of auto- induction, level at one month is useful, but no further induction expected after then



CBC



At one week, one month, three months, yearly



Occurrence of leukopenia rare, occurs within one month



Sodium



At one week, yearly



Uncommon side effect



LFTs



At two weeks, then yearly, unless symptoms of hepatitis



Actual hepatitis very rare



Lamictal (lamotrigine) 




No labs required; warn patients of rash risk





Trileptal (oxcarbazepine) 



Baseline Na, after one month, then as needed



Hyponatremia occurs in 3% of patients



Topamax (topiramate)





Baseline serum bicarbonate, after one month, then as needed



Metabolic acidosis (decreased bicarbonate) occurs in up to 50% of patients



Notes:


--Recommendations extracted from articles resulting from Pubmed searches of data pertaining to this topic and manufacturer’s information from the Physician’s Desk Reference. “B/l” = baseline; “LFT” = liver function tests; “TSH” = thyroid stimulating hormone


 

 
General Psychiatry
KEYWORDS laboratory_testing_in_psychiatry
www.thecarlatreport.com
Issue Date: August 1, 2007
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Table Of Contents
Screening Labs for New Patients: Are they Useful?
Laboratory Monitoring When Prescribing Psychotropics
Pharmacogenetic Testing in Psychiatry
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