3
Introduction to the HADI
This handbook offers a quick guide o possible
adverse effec s of drug in erac ions, wi h brief
recommenda ions for precau ionary measures.
Pairs of in erac ing drugs are lis ed alphabe i-
cally, followed by he adverse in erac ion, i s
mechanism (in paren heses), references and
recommenda ions for clinical managemen .
These lis ings are usually based on clinical re-
por s. In erac ions lis ed for groups of drugs
(such as “cephalosporins” or “an idepressan s,
ricyclic”) may no have been repor ed for ev-
ery drug in he group; known excep ions o he
in erac ion are no ed.
I is no possible o de ermine he frequency of
mos in erac ions. When an in erac ion is docu-
men ed by one or wo case repor s ra her han
clinical s udies or repor s in many pa ien s, he
year of each repor is given as some indica ion of
frequency.
Repor s of in erac ions be ween more han wo
drugs have begun o appear in he medical li era-
ure. Where hese have been documen ed, hey
are no ed in he commen s under in erac ing pairs
of drugs.
CRITERIA FOR LISTING INTERAC-
TIONS –– New adverse in erac ions are con inu-
ally being repor ed; he absence of a lis ing in his
book does no necessarily mean ha drugs will
no in erac when given concurren ly. In erac ions
ex rapola ed from animal s udies or from in erac-
ions repor ed wi h rela ed drugs, may no be in-
cluded here.
In erac ions be ween general anes he ics and
drugs likely o be adminis ered during surgery,
such as au onomic drugs and local anes he ics, are
no included. In erac ions useful in herapy, such
as he increased plasma concen ra ion of penicil-
lin wi h concurren use of probenecid, are also no
lis ed. Drug combina ions should be looked up
under heir componen s.
Common addi ive effec s, such as occur wi h use
of wo an ihyper ensive agen s or wo cen ral-ner-
vous-sys em depressan s or wo drugs ha affec
blood clo ing, are generally no lis ed. Effec s ex-
pec ed from he mechanism of a drug’s ac ion,
such as ha of po assium on digi alis glycosides or
calcium on calcium-en ry blockers, and useful an-
agonis effec s, such as ha be ween a poison and
an an ido e, are also no included. Mos in erac-
ions of drugs wi h foods, beverages or o her nu ri-
en s are no lis ed, bu foods in erac ing wi h
monoamine oxidase inhibi ors are included.
MECHANISMS OF INTERACTIONS —
Gene ic differences can affec drug me abolism
and in erac ions. Some drugs can in erac by
changing he me abolism of o her drugs, ei her
hrough inhibi ion or induc ion of any of several
hepa ic enzyme ac ivi ies or hrough al era ions in
hepa ic blood flow. Many drugs are me abolized
by cy ochrome P450 isozymes. A reference able