Limited information indicates that maternal doses of trihexyphenidyl up to 4 mg daily together with haloperidol or risperidone did not produce any adverse effects in breastfed infants. Long-term use of trihexyphenidyl might reduce milk production or milk letdown, but a single dose is not likely to interfere with breastfeeding. The prolactin elevating effect of concurrent antipsychotic agents might counteract any prolactin lowering effect of trihexyphenidyl. During long-term use, observe for signs of decreased lactation (e.g., infant insatiety and poor weight gain).