3
Introduction to the HADI
This handbook offers a quick guide to pos-
sible adverse effects of drug interactions,
with brief recommendations for precaution-
ary measures. Pairs of interacting drugs are
listed alphabetically, followed by the ad-
verse interaction, its mechanism (in paren-
theses), references and recommendations
for clinical management. These listings are
usually based on clinical reports. Interac-
tions listed for groups of drugs (such as
“cephalosporins” or “antidepressants, tricy-
clic”) may not have been reported for every
drug in the group; known exceptions to the
interaction are noted.
It is not possible to determine the frequency of
most interactions. When an interaction is docu-
mented by one or two case reports rather than
clinical studies or reports in many patients, the
year of each report is given as some indication
of frequency.
Reports of interactions between more than two
drugs have begun to appear in the medical lit-
erature. Where these have been documented,
they are noted as comments under interacting
pairs of drugs.
UNDOCUMENTED INTERACTIONS ––
New adverse interactions are continually being
reported; the absence of a listing in this book
does not necessarily mean that drugs will not
interact when given concurrently. Interactions
extrapolated from animal studies or interac-
tions reported with related drugs, frequently
mentioned in other sources, such as the
manufacturer’s package insert may not be in-
cluded here.
Interactions between general anesthetics and
drugs likely to be administered during surgery,
such as autonomic drugs and local anesthetics,
are not included. Interactions useful in therapy,
such as increased plasma concentration of
penicillin with concurrent use of probenecid,
are also not listed. Drug combinations should
be looked up under their components.
Common additive effects, such as occur with
use of two antihypertensive agents or two cen-
tral nervous system depressants, are generally
not listed. Effects expected from the mechanism
of a drug’s action, such as that of potassium on
digitalis glycosides or calcium on calcium-entry
blockers, and useful antagonist effects, such as
that between a poison and an antidote, are also
not included. Most interactions of drugs with
foods, beverages, or other nutrients are not
listed, but foods interacting with monoamine
oxidase inhibitors are included.
