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Pharmacotherapy Series

Psychotropic Medication
Part 2: Use During Lactation

Candace S. Brown, PharmD, BCPP, CFNP

The postpartum period represents a time of high risk for the onset or recurrence of psychiatric illness. Women are at highest risk of developing postpartum "blues," which is sometimes followed by postpartum depression or psychosis.

Postpartum blues, also known as "baby blues," affects 50% to 80% of women after delivery, and is manifested primarily by mood swings. Intervals of anxiety, irritability, or tearfulness alternate with periods of feeling well. Sleeping difficulties may also occur. Symptoms usually arise 3 to 4 days after delivery, and tend to resolve by day 12. Women should seek medical attention for symptoms lasting longer than 2 weeks, as approximately 20% of those with postpartum blues go on to develop postpartum depression.¹

According to the most recent Diagnostic and Statistical Manual of Mental Disorders, postpartum depression is defined as a major depressive episode occurring within 4 weeks of childbirth.² However, other sources report that symptoms may not occur until 6 to 12 weeks following delivery, and may last for 6 to 12 months after birth.3 In addition to symptoms seen in major depression, postpartum depression may also include excessive concern for the baby, feelings of failure as a mother, fear of losing control, lack of interest in the baby, fear of harming the baby, anxiety, and obsession.³

Postpartum psychosis is rare, affecting 0.1% to 0.2% of women after childbirth.⁴ Presentation is often dramatic, with onset as early as the first 48 to 72 hours postpartum. In most cases, symptoms develop within the first 2 weeks after delivery, and include restlessness, irritability, and sleep disturbance. Patients' emotional status then deteriorates rapidly, and is characterized by depressed or elated mood, disorganized behavior, mood lability, delusions, and hallucinations.⁵ In extreme cases, risks of suicide and/or infanticide are high; these women often require hospitalization.⁵

Part 1 of this series reviewed the spectrum of possible effects of psychotropic drug use during pregnancy, and provided guidelines for clinical management of this unique patient population. Part 2 discusses psychotropic drug use in lactating women.

LACTATION
Most psychotropic medications pass into breast milk to some degree, mostly through the process of passive diffusion.^6,7 However, a drug's protein binding, lipid solubility, degree of ionization, and molecular weight also influence the extent of passage, as well as the amount that remains in the breast milk. In general, the less protein-bound, more lipid-soluble, and more weakly basic the drug, the more likely it is to diffuse into breast milk. Many psychotropic medications are weak bases that are highly protein-bound and lipid-soluble, so they are fairly likely to do so. Also, most psychotropic drugs have molecular weights of less than 400, which means that they are small enough to diffuse passively into milk.⁶

Infant Physiology
Infants' abilities to absorb, metabolize, and eliminate drugs determine how these drugs will affect them. Compared with adults, infants have a higher gastric pH, causing basic compounds, which remain un-ionized, to have higher absorption rates than do acidic compounds. Infants also have lower levels of albumin, resulting in higher amounts of free/unbound (and therefore active) medication.⁸ Liver metabolic enzymes are immature in infants, decreasing the rate of degradation of medication. In addition, neonates' kidneys have a glomerular filtration rate that is 30% to 40% of that in adults.⁷ Finally, the blood-brain barrier in newborns is not fully developed, and central nervous system concentrations of some lipid-soluble compounds may reach levels that are 10 to 30 times those in serum.⁹ As a result of all of these factors, medications that reach the serum in neonates, as compared with those that reach the serum of adults or children older than 6 months, are more likely to be active, less likely to be metabolized and excreted, and more likely to cross into the brain.

Milk-to-Plasma Ratio
Medication concentration in milk is frequently compared with the concentration in maternal serum to quantify the extent of passage; this is known as the milk-to-plasma ratio (M/P). In general, compounds that are weakly protein-bound, highly lipid-soluble, weakly basic, and small in molecular size have higher M/P ratios.¹⁰ Ratios greater than 1 indicate that the medication is present in higher concentrations in breast milk than in maternal serum. The higher the M/P ratio, the greater the infant exposure to medication.

RECOMMENDATIONS
In 1983, the American Academy of Pediatrics (AAP) Committee on Drugs first published a list of drugs transferred into human milk. Revisions were published in 1989 and 1994.¹¹ The committee's task was to assist physicians in counseling women who wish to breast-feed their infants despite the fact that they have a medical condition requiring drug treatment. The committee placed drugs into categories ranging from those that are usually compatible with breast-feeding to those that are contraindicated in lactating women. Assignment of a drug to a particular category was based on data gathered from a search of the medical literature; the lists have included only those drugs with information about passage into human milk or their effect on an infant. Because of the lack of data regarding antidepressants, antipsychotics, and anxiolytics, the committee was unable to issue recommendations regarding these drugs in the 1994 publication; more information was available regarding mood stabilizers, however (Table 1). As methodologies used to quantitate drugs in milk continue to improve, this information is constantly being updated. The next revision, which is expected to include information on psychotropic drugs, is eagerly anticipated by all practitioners. Table 2 lists data accrued thus far regarding psychotropic use during breast-feeding according to drug class, number of case reports, and frequency and type of neonatal adverse events.^10,12-15

Antidepressants
All antidepressants listed by the AAP Committee on Drugs are considered to have an unknown effect on nursing infants and may be of concern.¹¹ Because breast-feeding may be warranted or strongly desired in some antidepressant-treated women, however, recommendations for use of specific agents are generally made by experts using the most recent data available.

Tricyclic antidepressants (TCAs).—By tradition, TCAs have been the antidepressants of choice in postpartum disorders because of their proven efficacy and their long history of use. Although these drugs are effective in this regard, they may have troublesome side effects in mothers. Sedation may interfere with caregiving, and weight gain may reduce compliance. Most important, these drugs are lethal in overdose, and must be prescribed and monitored with care.

Fifteen studies involving 34 infants nursed by mothers using TCAs have been reported.¹² Dosages ranged from 25 to 300 mg daily in imipramine equivalents, and M/P ratios ranged from 0.5 to 3.7.¹² Only one adverse event was reported: reversible sedation and respiratory depression in an infant of a doxepin user.¹⁶ Studies on postnatal development are few, but reports on infants ingesting milk containing amitriptyline and imipramine showed normal development at 12 and 30 months, respectively.¹⁷

Amitriptyline, nortriptyline, desipramine, and clomipramine have not been found in infant serum in quantifiable amounts, and have produced no adverse effects in neonates.¹⁸ Among these TCAs, nortriptyline and desipramine are generally recommended because of their higher tolerability in the mother.¹ Given the adverse effects reported in the nursing infant of a doxepin-treated mother, women who use this TCA should probably refrain from breast-feeding until further information regarding its safety is available.

Selective serotonin reuptake inhibitors (SSRIs).—As well-tolerated, safe, and effective alternatives to TCAs, SSRIs are the antidepressants of choice in high-risk populations. Consequently, data are accumulating regarding their use during pregnancy and lactation.

The relationship between SSRI use and breast-feeding has been reported in 16 studies involving 61 infants.¹² Six of these studies evaluated 30 infants whose mothers were receiving fluoxetine. Maternal dosages ranged from 10 to 80 mg daily, M/P ratios ranged from 0.1 to 1.5, and infant plasma concentrations ranged from 28 to 340 ng per mL. Irritability was identified in two infants in separate case reports.^19,20 Cognitive/psychomotor development was normal in four infants exposed to fluoxetine for up to 13 months.¹²

Sertraline secretion in breast milk was evaluated in five reports involving 26 infants. In mothers receiving 25 to 200 mg daily, M/P ratios ranged from 1.9 to 4.0, and resulted in infant plasma concentrations of 0.5 to 64.4 ng per mL. In one study of 12 infants exposed to sertraline, no adverse events occurred, and normal development was observed at 12 months.²¹

Paroxetine was evaluated in two case reports.^12,22 No adverse events were reported in neonates of mothers receiving 20 mg daily (M/P ratio, 7.6). Similarly, no neonatal side effects were noted in two case reports of neonates whose mothers received fluvoxamine 100 to 200 mg daily (M/P ratio, 0.30).^23,24 One fluvoxamine-exposed infant showed normal development up to the age of 21 months.²³ One report on citalopram showed an M/P ratio similar to that of sertraline.²⁵

Based on the relatively large amount of data amassed on fluoxetine and sertraline, these drugs are considered the SSRIs of choice in nursing mothers. Even though the database is larger for these two agents than for any other antidepressants, information is still limited because of failure to report adverse events during lactation, and because drug manufacturers are not required to conduct extensive studies in this area. Sertraline may be preferred over fluoxetine because of its shorter half-life, less active metabolite, and lack of any adverse events reported in breast-feeding neonates to date. No evidence indicates that any of the other SSRIs are more or less suitable, however.

Other antidepressants.—Reports on venlafaxine, bupropion, trazodone, and nefazodone are scant. M/P ratios are frequently high, but with considerable variation; for example, they range from 2.5 to 8.6 for bupropion26 and 0.08 to 7.4 for nefazodone.²⁷ Illet et al studied three cases of breast-feeding women using venlafaxine, and reported M/P ratios of up to 4.7.28 One case report examined the passage of trazodone into breast milk following a single maternal dose.²⁹ The M/P ratio was low (0.14), but infant serum and clinical status were not reported. Given their high M/P ratios and the limited amount of information available on these antidepressants, they are not recommended in lactating women at this time.

Mood Stabilizers
Lithium.—The literature on lithium use during breast-feeding is sparse, involving only 10 infants. Maternal dosages of 600 to 1200 mg daily have resulted in M/P ratios of 0.3 to 0.8 and infant plasma concentrations of 0.03 to 1.4 mEq per L.¹³ In one case report, breast milk concentrations were approximately 50% of maternal serum concentrations.³⁰ Two adverse events have been reported. In the first case, a baby developed cyanosis, hypothermia, hypotonia, and a heart murmur within a few hours of birth but was completely normal by day 8.³¹ In the second case, a baby showed signs of lithium toxicity while suffering from an upper respiratory infection, but the baby recovered with discontinuation of breast-feeding.³² Because of the possibility of lithium toxicity in infants and limited information on its developmental effects, the AAP Committee on Drugs11 and most authorities advise against breast-feeding while using lithium.

If it is deemed necessary to use lithium, then infant serum concentrations and clinical status should be monitored carefully, with breast-feeding discontinued if adverse events are noted. Physical illness or infection in infants that results in dehydration can lead to a significant increase in serum lithium concentrations (the same process can occur in adults), thereby increasing the risk for lithium toxicity.13

Anticonvulsants—Valproic acid has generally been considered safe for breast-fed infants because it is highly protein bound and, thus, found in low concentrations in breast milk. Nine studies have reported on 34 infants who have been exposed to valproic acid.¹³ M/P ratios ranged from 0.01 to 0.^10,13,33,34 and infant serum concentrations ranged from 1.0 to 13.4 mg per mL.³⁴ One infant experienced adverse effects (thrombocytopenia and anemia), which reversed upon cessation of breast-feeding.¹³ It should be noted that children younger than 2 years who are exposed to valproic acid as a treatment, not via breast milk, are at risk for fatal hepatotoxicity. Although valproic acid is not risk-free, it appears to be relatively safe, and the AAP Committee on Drugs has classified it as compatible with breast-feeding.¹¹

The effect of carbamazepine has been examined in 50 breast-fed infants in 11 studies.¹³ Breast milk concentrations varied from 7% to 95% of maternal serum values,13 and a comparison between infant and maternal serum levels found them to be similar. Nine infants experienced adverse events, including drowsiness, irritability, and refusal to feed (n = 6);13 hepatotoxicity (n = 2);35,36 and seizure-like episodes (n = 1).³⁷ The AAP Committee on Drugs has classified carbamazepine as compatible with breast-feeding.¹¹

Given the possible hepatotoxic and hemopoietic effects of both valproic acid and carbamazepine, if either agent is used in nursing mothers, infant liver function, white blood cell count, and platelets should be monitored. Based on available data, both of these agents appear to be relatively safe in breast-feeding infants. Valproic acid, which is present in negligible concentrations, may be preferable to carbamazepine.

Antipsychotics
All antipsychotics listed by the AAP Committee on Drugs are considered to have an unknown effect on nursing infants and may be of concern.¹¹ Thus, if it is necessary to prescribe an antipsychotic agent for nursing mothers, clinicians should rely on the opinions of experts who have searched and evaluated the current literature.

Fourteen reports have described the effects of antipsychotics on 39 infants exposed during breast-feeding.¹⁴ Thirty-two of these infants were exposed to conventional antipsychotics, mainly chlorpromazine or haloperidol. Maternal dosages of chlorpromazine 50 to 1200 mg daily resulted in M/P ratios of 0.5 to 48 and infant plasma concentrations of 0.1 to 0.7 ng per mL. Maternal dosages of haloperidol 1.0 to 40.0 mg daily resulted in M/P ratios of 0.4 to 8.0 and infant plasma concentrations from 0.8 to 8.0 ng per mL. One report described drowsiness and lethargy in an infant exposed to chlorpromazine.³⁸ Another report described developmental delays in three of four infants exposed to both chlorpromazine and haloperidol at 1 to 4 months.¹⁴ Normal development was reported in two infants exposed to trifluoperazine at 11 and 30 months,¹⁴ and in one infant exposed to haloperidol from 6 to 12 months.³⁹

Most clinicians advise caution in mothers who are using haloperidol and chlorpromazine simultaneously or individually in high doses. Nevertheless, when antipsychotic treatment is necessary, low-dose haloperidol or chlorpromazine is recommended because of the more extensive data available on these agents and the relatively low incidence of adverse events.

Although case reports on the newer atypical antipsychotics have been published, they contain significantly fewer data than do reports on conventional antipsychotics. One case study of risperidone reported an M/P ratio of 0.42.⁴⁰ Olanzapine M/P ratios in five women ranged from 0.2 to 0.84.⁴1 M/P ratios for clozapine varied between 2.8 and 4.3 in one patient.⁴² Given the degree of clozapine passage into breast milk and the potential risk of fatal agranulocytosis from any clozapine dose,¹⁴ breast-feeding during maternal clozapine treatment should probably be avoided. Early reports on olanzapine and risperidone are promising because of the low M/P ratios, but additional studies are required before clinicians can be more confident of their safety. Even though atypical antipsychotics are being prescribed more widely, they are not recommended over traditional antipsychotics during breast-feeding because of the paucity of available data.

Anxiolytics
The AAP Committee on Drugs lists all anxiolytics as of concern in breast-feeding women because of their unknown effects in nursing infants.¹¹ In situations where maternal anxiolytic treatment is necessary, clinicians should rely on experts' opinions formulated from recent, evidence-based data.

Reports have described 36 infants exposed to benzodiazepines (eg, diazepam, temazepam, alprazolam, lorazepam, clonazepam).¹⁵ Maternal dosages of diazepam 30 to 190 mg daily produced an M/P ratio of 0.1 and infant serum concentrations of 31 to 243 ng per mL.¹² Clinical status was reported in 18 of the 36 infants exposed to benzodiazepines; 14 showed no ill effects. Adverse reactions that did occur involved infants whose mothers were using benzodiazepines with long half-lives. Among 10 infants exposed to diazepam, two were sedated, with one baby also losing weight. Among two infants exposed to clonazepam both in utero and postpartum, one had low Apgar scores at birth but was well at 5 months. One infant exposed to alprazolam experienced a withdrawal syndrome at 1 week postpartum when breast-feeding ceased. None of the 10 infants exposed to temazepam had any adverse effects. Studies on the long-term effects of benzodiazepines on breast-fed infants have not been conducted.

These data suggest that benzodiazepines with long half-lives and active metabolites (eg, diazepam, clonazepam) should probably be avoided. Shorter-acting benzodiazepines without active metabolites (eg, temazepam, lorazepam, alprazolam) are favored, but weaning should be very gradual to avoid withdrawal symptoms. Infants should be monitored for sedation or poor feeding. Clinicians might want to consider using a low-dose, sedating TCA instead of a benzodiazepine in lactating mothers who require prolonged anxiolytic or sedative/hypnotic medication.

TREATMENT GUIDELINES
Use of nonpharmacologic interventions, an increase in support systems, and a reduction of stressors may be sufficient in cases of mild depression or anxiety, and should be implemented in all women as an adjunct to medication. For more severe postpartum depression or postpartum psychosis, electroconvulsive therapy may be an option.

Decisions should be collaborative between physician and patient whenever possible, and the risk/benefit ratio should be discussed with the mother and her partner. Invariably, the decision is based on a calculated risk. For example, if a woman has a history of relapse when unmedicated or if a past depressive episode was severe, the direct benefits for the mother and the indirect benefits for the infant would outweigh any potential risks to the infant. Table 3 summarizes general treatment guidelines for use of psychotropics during breast-feeding.¹⁰

Infant Assessment
Before exposure to a psychotropic agent, infants should receive a thorough clinical assessment by a pediatrician, providing a baseline for future comparison. Use of an agent with a low M/P ratio can help to minimize infant exposure. Only infants who are both at term and do not suffer from any organ dysfunction that may impair drug clearance should be exposed to medication. Use of the minimum effective dose is always advisable, and monotherapy should be chosen if possible.

Risk Factor Evaluation
Although data collected thus far are very limited, they provide some guidance regarding the use of psychotropic agents in nursing mothers. Women who require an antidepressant are best treated with TCAs such as nortriptyline or desipramine, or with SSRIs such as sertraline or fluoxetine. Valproic acid and carbamazepine are the agents of choice in those requiring mood stabilization. Psychotic episodes are best treated with low doses of haloperidol or chlorpromazine. Anxiety symptoms should be managed with a short-acting benzodiazepine such as lorazepam, alprazolam, or temazepam.

Monitoring
Infant serum concentrations of medication and metabolites should be monitored; breast-feeding can be discontinued if levels are higher than negligible. Infants should be followed regularly for any change in clinical status. Cessation of breast-feeding should be considered if symptoms arise.

Timing
Breast-feeding should be timed to occur when drug levels in breast milk are lowest. Mothers should breast-feed before, not after, taking the drug. Short-acting medications are preferable to long-acting ones, and should be taken as a single dose immediately after breast-feeding if possible, as this may decrease infant exposure. Mothers can store breast milk from non-peak periods to use during peak periods.

CONCLUSION
Methodologically rigorous data on the effects of maternal psychotropic drug use on breast-fed infants are only beginning to emerge. These small, mainly uncontrolled, short-term studies highlight the need for systematic, longer-term follow-up studies. More sensitive and reliable assay methods will also be required to measure infant plasma levels, thereby enabling a more accurate estimation of exposure.

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