Transcript PSYC650 Interactions and RxP

PSYC650
Psychopharmacology
Drug Interactions and
Prescriptive Authority for
Psychologists
I got a grip of drugs…
• 320 mg methadone (opiate; 40 mg/d max for opiate
dependence)
• 32 mg clonazepam (Klonopin; Benzo, 20 mg/d max for seizure
disorder)
• 160 mg temazepam (Restoril; Benzo, 30 mg for insomnia)
• 290 mg propranolol (Inderal; Beta Blocker, 640 mg/day max for
angina)
• 2 tablets of Vicodin of unknown dose (probably 500/5)
– Acetominophin and hydrocodone (max 8 tabs/24-h)
• 1.5 g “Kind Bud” (Good quality marijuana)
• 4 g “Mersh” (Poor quality marijuana)
• “Some 151” (Usually rum)
i told u i was hardcore
All Drug interactions are to
be avoided
Strongly Agree
Agree
Disagree
Strongly Disagree
100%
0%
Di
s
is
a
ag
re
e
gr
ee
gr
ee
0%
ly
St
ro
ng
St
ro
ng
ly
Ag
re
e
0%
D
What about naloxone or disulfiram?
A
1.
2.
3.
4.
25%
0%
0%
ag
re
e
gr
ee
Di
s
is
a
ly
A
gr
ee
D
St
ro
ng
ly
Ag
re
e
Careful dosing and timing
St
ro
ng
1.
2.
3.
4.
It’s sometimes okay to give/take
drugs that you know will have
negative interactions
Strongly Agree
75%
Agree
Disagree
Strongly Disagree
Most interactions are
immediate
1. True
2. False
100%
ls
e
Fa
Tr
ue
0%
Which of the following
impact the significance of a
drug interaction?
1. Dose
2. Route of
administration
3. Kidney function
4. Liver function
40% 40%
20%
0%
R
ou
te
ct
io
n
ve
rf
un
Li
ey
fu
n
ct
io
n
n
id
n
in
is
tr
at
io
K
of
ad
m
D
os
e
Actually, it’s all of the above…
To avoid drug interactions, use herbs
instead because they are safer and do
not interact with medications.
1. True
2. False
100%
ls
e
Fa
Tr
ue
0%
Herbal Interactions
• Black Cohosh
– Increased SSRI and TCA ADRs
• Ginko Biloba
– Potentially dangerous rise in trazodone efficacy (Desyrel;
SSRI)
• Milk Thistle
– Dangerous rise in efficacy and ADRs for “sedatives”
• St. John’s Wort
– Reduced efficacy in SSRIs
– Increased ADRs for TCAs
– Increaed ADRs for migraine meds
Dealing with ADRs
•
•
•
•
•
Get current and detailed drug histories
Give least possible number of adjuncts
Avoid changing pharmacotherapy
Be careful with narrow TIs
Monitor for interactions whenever changing
pharmacotherapy
• Keep in touch with prescribers
• Keep your patients informed!
Pharmacodynamic
Interactions
• Occur at the site of action
• Alcohol and barbiturates
• Anticholinergic compound with drug that has
anticholinergic ADRs
• Naloxone and Heroin
Pharmacokinetic
Interactions: Input
• Tetracycline is the classic example
– Don’t take with food: cations bind and decrease free drug
available
• L-DOPA increases absorption
• Nutrient
– BRAT diet
– pH changes
– Affect bile secretion
• Also goes the other way with foods
– Alcohol altering B6
– Anorectics or nausea-inducing drugs
– Constipation or diarrhea
Distribution
• Lithium and salts
• Phenytoin displaces warfarin
– Can also create greater concentrations in parts of
the body, thus promoting hemorrhage
Output
• Enzyme induction
– Increases hepatic metabolism
– Takes 2-3 weeks to take full effect
– Auto-induction (Tegretol & Trileptal)
• Enxyme inhibition
– MAOIs increase sympathomimetic amines (E, NE)
– Prozac occupies enzymes that break down 5-HT (competition for
enzymes)
– Disufiram and alcohol
• Kidney excretion
– Competes for renal tubular secretion
– Lithium and diuretics
• Increases renal salts, decreases Lithium excretion, increases Lithium levels
T’s and Blues
• Pentazocine (Talwin; mild
opiate) + tripelennamine
(antihistamine)
• Synergistic effect roughly
equivalent to Heroin
• Used when Heroin not
available
• Seizures and death
– More prevalent in crowded
living arrangements
Phen-Fen
• Fenfluramine
– 5-HT releaser
– Suppresses appetite
– Drowsiness
• Phentermine
– Dopamine agonist
– Suppresses appetite
– Combats drowsiness
Phen-Fen
• 1992 study demonstrated a loss of 30 lbs on average
for 121 obese patients
– Starting shot for the Phen-Fen craze
• No safety studies
–
–
–
–
Speeds up lungs
Increases gastric juices
Sped up heart rate
Irreversible and reversible pulmonary hypertension
• Pulled off the market in 1997
– 24 cases of heart valve damage noted in women who had
used Phen-Fen for 1 year
1.
2.
3.
4.
Common ADRs for
stimulant medications
include:
Weight gain
Apathy
Hallucinations
Insomnia
Your patient on Haldol appears sweaty, more
confused than usual, has a high fever, and is
experiencing painful muscle rigidity. What’s
going on?
1. Serotonin Syndrome
2. Serum Sickness
3. Neuroleptic
Malignant Syndrome
4. Extrapyramidal Side
Effects
al
Si
de
na
n
Ex
tr
ap
y
ra
m
id
M
al
ig
tic
ro
le
p
eu
E.
..
...
s
kn
es
Si
c
ru
m
Se
N
Se
ro
to
n
in
Sy
nd
ro
m
e
25% 25% 25% 25%
10
Strongly Agree
Agree
Disagree
Strongly Disagree
ag
re
e
gr
ee
Di
s
is
a
ly
St
ro
ng
A
gr
ee
D
ly
Ag
re
e
25% 25% 25% 25%
St
ro
ng
1.
2.
3.
4.
I feel that, with sufficient training,
Psychologists should be permitted the
authority to prescribe psychoactive
medications.