Further investigation

Is there anything else you would especially like to know about this patient?

What about his collaborating pediatrician and his findings?

• – A release of information is obtained

• – The pediatrician states that starting the fluoxetine SSRI clearly promoted secondary enuresis at the higher 20 mg per dose

• – It is not clear if the weight loss and growth retardation is from the SSRI, the multiple stimulant trials, his genetics, or normal, as he has not fallen off his growth curve yet

• – His height and weight trajectories have diminished but are not an imminent problem

• – The pediatrician suggests that psychotropics continue to be prescribed as his psychiatric symptoms are the most disruptive and problematic now

• – He will consider endocrine and developmental geneticist consultations if these adverse effects worsen and become a clinical dilemma

• – He confirms there are no cardiac concerns for this patient and approves use of stimulants. An EKG is not warranted

Is there any reason why he might be vulnerable to side effects from his low-dose psychotropics?

• – Fluoxetine (Prozac) is clearly known as a strong inhibitor of the CYP450 2D6 isoenzyme system in the liver

  • Psychopharmacologists often have to lower doses of other augmentation agents, such as aripiprazole, atomoxetine, desipramine, etc., when fluoxetine is part of the regimen

  • Amphetamine stimulants are a substrate for CYP450 2D6 and may need to be lowered when combined with fluoxetine in some patients, or they may experience stimulant intoxication or toxicity

  • Methylphenidate-based stimulants are unlikely to be subject to a drug–drug interaction involving his SSRI via CYP450 isoenzymes

Case outcome: first interim follow-up visit two months later

Between sessions, parents agree to increase lisdexamfetamine (Vyvanse) to 30mg/d and taper off fluoxetine (Prozac), as it is still thought to be the primary reason for weight loss

ADHD symptoms improve markedly at school

At home, there is still great difficulty in the mornings and late afternoons when the stimulant is not at peak plasma levels

Enuresis resolves with tapering off of fluoxetine and he has no acute side effects from lisdexamfetamine increased dosing

His pediatrician feels that annual monitoring is adequate for his height and weight

He is 51 in and 56 lbs and has not lost weight recently

All are happy with the patient’s continued lack of anxiety recurrence and ongoing moderate ADHD improvements

Question

The patient has morning and late afternoon breakthrough ADHD symptoms; what might you suggest?

Increase the stimulant in the morning

Wake the patient up briefly an hour before his usual waking time and administer his stimulant then to improve morning symptom control

Even though his stimulant is approved once daily, administer a smaller booster dose at lunch-time at school for better afternoon/evening symptom coverage

As his stimulant is considered long acting, augment with a shorter-acting, amphetamine-based stimulant (d/l-amphetamine [Adderall]) in the morning and/or afternoon for better symptom control

Augment his stimulant with a nonstimulant, longer-acting ADHD medication such as atomoxetine (Strattera), guanfacine-ER (Intuniv), or clonidine-ER (Kapvay)