44

THE PROSPECT OF AMANTADINE FOR PREVENTION OF INFLUENZA A2 I N HUMANS (EFFECTIVENESS OF AMANTADINE DURING INFLUENZA A2/HONG KONG

EPIDEMICS I N JANUARY-FEBRUARY , 1 9 6 9 I N LENINGRAD)

Anato l i A.Smorodintsev, George I .Karpuchin, Dimitry M.Zlydnikov, Anna M.Malysheva, Evgenya G.Shvetsova, Sergey A.Burov, L id ia M. Chramtsova, Yury A.Romanov, Ludmila Yu.Taros, Yury G.Ivannikov and Sergey D.Novoselov

All-Union Research I n s t i t u t e of Inf luenza USSR Minis t ry of Publ ic Health

Leningrad

INTRODUCTION

Inf luenza r ep resen t s one of t he few i n f e c t i o u s d i seases known t o cause short- term, explos ive mass outbreaks. In f lu - enza A epidemics occur r egu la r ly a t i n t e r v a l s of 2 t o 3 years and a f f e c t up t o 50% of t h e populat ion of a l l age groups. Hence, more genera l and s p e c i f i c measures a r e requi red t o c o n t r o l inf luenza,which i s a problem of s p e c i a l s c i e n t i f i c and p r a c t i c a l importance. I n r ecen t years a new promising drug , amantadine hydrochlor ide, was developed by E . I. du Pont de Nemours & Co. and used f o r t h e o r a l chemo- prophylaxis of in f luenza . l - l 2

Inves t iga t ions c a r r i e d out i n 1967 and 1968 by Smorodintsev, e t a 1 . , I 3 showed amantadine hydrochlor ide t o be an e f f e c t i v e prophylac t ic drug when adminis tered t o vol- un teers i n d a i l y doses of 1 0 0 o r 2 0 0 mg begun 2 4 hours before chal lenge wi th ae roso l s of l i v e in f luenza A2 v i r u s vaccines made up sepa ra t e ly of t he s t r a i n s A2/21/1965 , A2/133/1967, and A2/Hong Kong/1/1968. The medicat ions, e i t h e r placebo o r amantadine H C 1 a t a d a i l y dose of 1 0 0 or 200 mg', were con- t inued f o r 11 days.

I n t h e placebo group 80% o r more of t h e s u s c e p t i b l e s u b j e c t s responded t o t h e l i v e in f luenza vaccine cha l lenge wi th gene ra l c o n s t i t u t i o n a l and c a t a r r h a l c l i n i c a l symptoms of var ious i n t e n s i t y . Amantadine adminis tered a t a dose of 100 mg p e r day w a s found t o prevent c l i n i c a l i l l n e s s i n 55% of t h e volunteers . Furthermore, t he s e v e r i t y and du ra t ion of t h e symptoms i n t h e s u b j e c t s who became ill w e r e dimin- i shed i n t h e drug-dosed when compared t o those given placebo A sharp 2-fold decrease i n t h e frequency and i n t e n s i t y of t h e immune response t o the l i v e v i r u s inoculum was a l s o observed i n the drug group when compared t o t h e placebo group.

45

Figure 1 shows t h e incidence of more d i s t i n c t c l i n i c a l and a l s o immunological r eac t ions t o t h e l i v e v i r u s cha l lenges i n volunteers i n r e l a t i o n t o t h e i r i n i t i a l serum in f luenza A2 antibody l e v e l . Following chal lenge wi th inf luenza A2 v i r u s , t he placebo group with p r e e x i s t i n g low antibody l e v e l s of 0 t o 1:16 proved h ighly suscep t ib l e ; t h e middle group with antibody l e v e l s of 1:32 t o 1:64 moderately so, while t h e group with the h ighes t antibody l e v e l s responded even less.

INITIAL FEBRILE LEVELOF REACTIONS

AMTI BODIES ( 37.6O AND IN HI T€ST HlGHER)

0-l:16 An. 42 PI. 38

4 1:32 - 1:64 5 Am.84 Z PI. 98 8

CLINICAL REACTIONS

OF 3 1 DEGREE

SEROLOGICAL RESPONSE

~ 4- FOLO M I BODY RISE ANDYOREI

.... . . ....'.

Figure 1. Corre la t ion of t h e i n i t i a l l e v e l of serum antibody t o inf luenza A2 v i r u s with t h e i n t e n s i t y of the s e r o l o g i c a l response and t h e f e b r i l e and c l i n i c a l r eac t ions t o l i v e inf luenza A2 v i r u s vaccines i n volunteers r ece iv ing amanta- d ine HC1 o r placebo.

46

In t ens ive f e b r i l e and other c l i n i c a l r eac t ions were e f f ec - t i v e l y suppressed by amantadine i n a l l groups of s u b j e c t s , b u t e s p e c i a l l y i n t h e more immune groups. The s e r o l o g i c a l response was most markedly reduced i n t h e h ighly suscep t ib l e group. These observa t ions may exp la in a l s o t h e pronounced inc rease i n e f f i c a c y of amantadine when preceded by l i v e in f luenza v i r u s vacc ina t ion r ecen t ly found by t h e au thors .

The marked p r o t e c t i v e e f f e c t s of amantadine observed i n these c l i n i c a l t r i a l s on volunteers provided t h e bases* f o r f u r t h e r s t u d i e s of t h e epidemiological e f f e c t i v e n e s s of t he drug dur ing an ex tens ive outbreak of i n f luenza A2/Hong Kong i n January-February, 1 9 6 9 i n Leningrad.

MATERIALS AND METHODS

The experiments w e r e c a r r i e d o u t by t h e s t a f f s of t he Epidemiological and C l i n i c a l Departments of t h e All-Union Research I n s t i t u t e of Inf luenza wi th t h e p a r t i c i p a t i o n of s p e c i a l l y organized epidemiological teams.

S i x semi- i so la ted populat ions of a d u l t s u b j e c t s between the ages of 18 and 30 years w e r e s e l e c t e d t o p a r t i c i p a t e i n t h e study. The t o t a l s tudy populat ion cons i s t ed of 10053 sub jec t s . Ind iv idua l popula t ions ranged i n s i z e from 1 2 0 0 t o 2000 people. Thei r working and l i v i n g condi t ions were e s s e n t i a l l y the same. They w e r e r egu la r ly observed by q u a l i f i e d medical personnel , and those who developed i n f l u - enza during t h e s tudy i n January-February, 1 9 6 9 w e r e hosp i t a l i zed .

Each populat ion was d iv ided randomly i n t o two compar- a b l e groups of equal s i z e - t he experimental (amantadine- dosed) s tudy group and the c o n t r o l groups (Figure 2 ) . The s u b j e c t s i n t h e con t ro l groups rece ived placebo (placebo group) o r no medication ( t h e i n t e r n a l c o n t r o l g roup) , o r

"Further suppor t f o r t h e p r o b a b i l i t y t h a t amantadine H C 1 would be e f f e c t i v e a g a i n s t t h e causa t ive in f luenza A2 v i ruses of t h i s epidemic came from t h e labora tory s t u d i e s of C.E.Hoffmann, Ph.D., and h i s a s s o c i a t e s , a t t h e S t i n e Lab- o r a t o r i e s , E. I. du Pont de Nemours & Co., Newark, Delaware. Using l abora to ry models of i n f e c t i o n s with in f luenza A2/Hong Kong/8/68 and A2/Hong Kong/50/68, they w e r e ab l e t o show t h a t these v i ruses were s e n s i t i v e t o the a n t i v i r a l a c t i v i t y of amantadine HC1. Subsequent s i m i l a r l abora to ry s t u d i e s wi th i s o l a t e s from t h i s outbreak, A2/Leningrad/21/69 and A2/Leningrad/74/69, showed t h a t t hese v i ruses a l s o w e r e sen- s i t i v e t o amantadine HC1.

47

comprised a sepa ra t e group of s&]ects excluded from any medication and who p a r t i c i p a t e d i n t h e s tudy a s e x t e r n a l con t ro l s i d e n t i c a l i n a l l l i v i n g condi t ions wi th t h e o t h e r s tudy groups.

- AMANTADlNE GROUP

- PLACEBO 6RWP

- EXTERNAL CONTROL

0 - INTERNAL CONTROL

Figure 2 . The d i s t r i b u t i o n of t h e s tudy populat ions in - volved i n a c l i n i c a l t r i a l of t h e epidemiological e f f ec - t i veness of amantadine HC1 dur ing an outbreak of i n f luenza AZ/Hong Kong i n Leningrad dur ing January-February, 1969.

Of t h e 10053 observed unvaccinated ind iv idua l s , 50.7% received amantadine, and 31.6% placebo medicat ions; 10% of t h e t o t a l populat ion was involved a s the i n t e r n a l c o n t r o l and 7 .7% a s t h e e x t e r n a l c o n t r o l groups. The i n t e r n a l con- t r o l group d i f f e r e d from t h e amantadine and placebo groups, being less i s o l a t e d from t h e municipal populat ion while t h e e x t e r n a l c o n t r o l group was s i m i l a r t o amantadine o r placebo groups i n t h i s r e spec t .

The in f luenza A2/Hong Kong* epidemic occurred i n Leningrad a t the end of t h e f i r s t week of January, 1969 and reached its peak by the end of t h a t month. The populat ions i n t h e d i f f e r e n t i n s t i t u t i o n s were involved i n the l o c a l i z e d outbreaks a t d i f f e r e n t t i m e s . A morbidi ty r a t e t w i c e normal was an ind ica t ion f o r t h e s t a r t of s tudy medication. I n t h r e e groups, t h e i n i t i a t i o n of dosing coincided wi th t h e i n i t i a l s t a g e s of t h e development of t h e outbreaks, and i n th ree groups prophylaxis was begun j u s t before t h e peak of morbidity was reached.

48

Amantadine hydrochlor ide, suppl ied by E . I . du Pont de Nemours & Co., was given i n capsules o r a s a syrup; corres- ponding placebos w e r e of i d e n t i c a l appearance.

The amantadine HC1 ( 1 0 0 mg) o r placebo capsules were adminis tered o r a l l y once d a i l y a f t e r t h e evening meal. Amantadine was a l s o success fu l ly adminis tered a s a syrup i n f r u i t j u i c e s i n t h e same dose of 1 0 0 mg once d a i l y . I n t h e major i ty of t h e groups dosing continued f o r 30 days; i n popula t ions 3 and 5 amantadine admin i s t r a t ion l a s t e d f o r 1 2 days.

Medications i n t h e var ious s tudy popula t ions w e r e randomly coded and adminis tered by a double-bl ind design. Co-ding was d i f f e r e n t f o r each populat ion. The drug code was broken only a f t e r a l l s t a t i s t i c a l ana lyses of t h e mor- b i d i t y f ind ings were completed.

Medication was d i s t r i b u t e d by t h e t r a i n e d s t a f f s of t h e epidemiological teams. Using s p e c i a l c h a r t s , t h e same teams k e p t accu ra t e records of t h e drug d i s t r i b u t i o n s . Medical personnel i n charge of t h e popula t ions observed and t h e s t a f f from t h e Inf luenza I n s t i t u t e cont inuously con- t r o l l e d t h e c o r r e c t d i s t r i b u t i o n s of medication.

Af t e r te rmina t ion of t h e prevent ive program, 1825 non- ill s u b j e c t s p a r t i c i p a t i n g i n t h e s tudy were randomly i n t e r - viewed by t h e s t a f f , who c o l l e c t e d and analysed t h e answers recorded i n s p e c i a l coded c h a r t s t o ensure double-blind eva lua t ions of s i d e e f f e c t s .

Since a l l s tudy groups w e r e under complete medical sup- e r v i s i o n , it was poss ib l e t o d e t e c t and t o h o s p i t a l i z e p a t i e n t s wi th c l i n i c a l l y diagnosed inf luenza . A case h i s - t o r y was recorded f o r each ill subject. The r e s u l t s of dosing were eva lua ted t ak ing i n t o cons ide ra t ion t h e du ra t ion and r e g u l a r i t y of dosing, any s i d e e f f e c t s , t h e gene ra l c l i n - i c a l p i c t u r e of t h e d i s e a s e , and s e r o l o g i c a l f i nd ings .

The e t io logy of t h e i l l n e s s was confirmed a s in f luenza A2 by us ing both the complement f i x a t i o n and hemagglutin-

*Inf luenza A-type v i r u s e s w e r e i s o l a t e d from t h e popula t ions and w e r e determined t o be a n t i g e n i c a l l y s i m i l a r t o in f luenza A2/Hong Kong/1968 s t r a i n s suppl ied by Dr.H.Pereira, WHO Inf luenza Surve i l l ance Laboratory, London, England. Isol- a t e s from t h e p re sen t s tudy outbreak have been i d e n t i f i e d a s i n f luenza A2/Leningrad/69.

49

a t i o n i n h i b i t i o n * s e r o l o g i c a l tests performed on pa i r ed heated s e r a . The acute specimens w e r e co l l ec t ed during t h e f i r s t days of i l l n e s s followed by t h e convalescent specimens 3 t o 4 weeks l a t e r .

The epidemiological e f f ec t iveness of amantadine was ca l cu la t ed i n comparisons o f t h e morbidi ty r a t e s among t h e subjects of t h e c o n t r o l and experimental groups and expressed as an index of e f f ec t iveness . The index of e f f e c t i v e n e s s ( I E ) and the index of p r o t e c t i v e e f f e c t ( I P E ) ( a l s o descr ibed a s c o e f f i c i e n t of e f f ec t iveness ) w e r e based on t h e incidences of c l i n i c a l i l l n e s s e s . The index of e f f ec t iveness was calcu- l a t e d a s fol lows:

p1

p 2

I E = _-_-__

where PI and P2 i n d i c a t e inf luenza o r acute r e s p i r a t o r y d i sease morbid i t ies i n t h e c o n t r o l and experimental groups r e spec t ive ly . When analysing t h e c l i n i c a l r e s u l t s supported by s e r o l o g i c a l f i nd ings , a co r rec t ed index of e f f e c t i v e n e s s w a s ca l cu la t ed by t h e equat ion:

where P1 and P2 a r e a s above; P i and P' a r e t h e frequences of in f luenza dlagnoses confirmed by l a i o r a t o r y tes ts i n t h e r e spec t ive groups.

The confidence l i m i t s f o r t h e ind ices of e f f ec t iveness were ca l cu la t ed by t h e equat ions:

where Pmin and Pmax a r e t h e minimal and maximal va lues of confidence i n t e r v a l s f o r t h e appropr i a t e p r o b a b i l i t i e s .

*Inf luenza A2/Leningrad/69 and in f luenza A2/21/65 hemagglu- t i n i n w e r e used.

50

The confidence i n t e r v a l s f o r i l l n e s s p r o b a b i l i t y were made by approximation of binomial d i s t r i b u t i o n s using Poisson or Gaussian d i s t r i b u t i o n s . I f t h e confidence l i m i t s f o r morbidi ty were made with a confidence l e v e l of a, then t h e confidence l e v e l f o r t h e confidence i n t e r v a l of t h e index of e f f ec t iveness would be aka.

F i n a l l y , t he index of p r o t e c t i v e e f f e c t was determined by t h e equat ion:

RESULTS

dine some of t he s u b j e c t s missed r egu la r medication due t o t h e i r temporary absence from t h e groups. Considering it s i g n i f i c a n t t h a t amantadhe i s c l e a r e d from t h e organism i n approximately 3-5 days, t h e ana lyses d i s t ingu i shed between those on continuous o r i r r e g u l a r medication schedules . Those who took amantadine wi thout i n t e r r u p t i o n dur ing t h e e n t i r e per iod of s tudy comprised t h e major i ty of p a r t i c i p a n t s (84 .9%); 10.4% w e r e given medication i r r e g u l a r l y o r were absent from t h e s tudy f o r 1-7 days. m a n t a d i n e o r placebo dosing was not given f o r 8 or more days i n 4 . 7 % of t h e sub- jects; hence, they w e r e no t included i n the analyses of t h e r e s u l t s .

During t h e course of t h e prevent ive program wi th amanta-

The var ious analyses of t h e epidemiological e f f e c t i v e - nes s of amantadine are shown i n Tables 1 and 2.

Table 1 summarizes t h e r e s u l t s ob ta ined i n 4559 persons who r e g u l a r l y o r i r r e g u l a r l y received amantadine and of 2804 who rece ived placebo. The mean index of amantadine e f f ec - t i veness according t o t h e c l i n i c a l f ind ings was 1 .7 and w i t h t h e s e r o l o g i c a l co r rec t ion f o r confirmation of i n f luenza A2 i l l n e s s 2.19 (see equat ion B above) . The i l l n e s s e s i n one populat ion w e r e confirmed by complement f i x a t i o n s e r o l o g i c t e s t i n g a s i n f luenza A i n 32.0% of t h e amantadine group and i n 41.2% of t h e placebo group.

The f ind ings presented i n Table 2 sugges t t h a t t h e amantadine e f f e c t i v e n e s s i n t h e group which r egu la r ly received the drug was almost two t i m e s a s high a s i n t h e placebo group (1.95) and even more (2.15) wi th t h e se ro log i - c a l co r rec t ion . Among t h e s u b j e c t s i r r e g u l a r l y r ece iv ing amantadine e f f e c t i v e n e s s was lack ing (IE = 1.1).

51

STAT1 STlC A L PARTI TI ON I AYANTAOINE

Table 1 Epidemiological Effectiveness of Amantadine HC1

Among Subjects Regularly or Irregularly Receiving the Drug During an Influenza

A2/Hong Kong Epidemic in January-February,l969 in Leningrad

PLACEBO

9 a 8E IL

-I

n a 8 2 * x s w w

NO. OF SUBJECTS OBSERVED I 4 5 5 9 I 2804

NO. OBSERVED I28 119 POSITIVE 41 4 9

% 32 .O 41.2

” YEAN 2.19 LOWER 1.26 UPPER 4.27

YEAN S0.6 LOWER 54.34 UPPER 76.6

x W

p

g g

-

I 224 21 4 I [ NO.OFCASES

I) Index of effectivrrmr f flc , where P, 6 P, are the morbidity rates

2) Index of protective rffect(oh)= 9 .lo0

3) Corrected for serologic camfirmation of influenza A 2

PI of respiratory illnesses in the control and drug-dosed groups resprctivdy.

Tab

le 2

Epid

emio

logi

cal

Effe

ctiv

enes

s of

Aman

todin

e HC

I Am

ong

Subj

ects

Reg

ular

ly R

ecei

ving

the

Drug

Dur

ing

Influ

enza

A,

Outb

reak

sh L

enin

grad

in Ja

nuar

y- F

ebru

ary,

196

9

CLI

NIC

AL

FIN

DIN

GS

1

I)

Leve

l of e

ffec

liven

eu b

owd

on c

linic

al d

iagn

osis

onl

y.

1)

Leve

l of

effe

ctiv

enes

s co

rrec

ted

by s

erol

ogic

al re

sults

for

conf

irmal

ion

of in

fluen

za i

llnes

s w

Thew

fig

ures

are

der

ived

from

com

para

tive

data

on

mor

bidi

ty a

mon

g su

bjec

ts o

f ex

tern

al c

ontro

l gro

up N

o.6

(88

per

100)

. 4

) In

dex

of m

orbi

dity

for

mun

icip

al p

opul

atio

n w

as c

alcu

late

d du

rinq

lhe

perio

d of

obs

erva

tion

of t

he e

xper

imen

tal g

roup

.

53

The r e s u l t s of t h e p r o t e c t i v e e f f e c t of amantadine a r e much more pronounced when comparisons a r e made of t h e mor- b i d i t y r a t e s among the s u b j e c t s of t h e amantadine and of t h e i n t e r n a l c o n t r o l groups wi th an index of e f f e c t i v e n e s s of 5.32 and a p r o t e c t i v e c o e f f i c i e n t of 81.2%. Comparisons with t h e e x t e r n a l group g ive an I E of 3.08 and p ro tec t ion of 6 7 . 6 % ; with t h e municipal c o n t r o l (an a d d i t i o n a l e x t e r n a l con t ro l ) an I E of 5.34 and p ro tec t ion of 81.3%.

The morbidity r a t e s i n t h e t o t a l s tudy popula t ions , i . e . , f o r t h e amantadine and placebo groups, were i n i t i a l l y s i m i l a r wi th t h e e x t e r n a l c o n t r o l group i n t h e beginning of t h e outbreak (Figure 3). Late r t h e dosed groups showed only an i n s i g n i f i c a n t rise i n morbidity a f t e r i n i t i a t i o n of t rea tment while a hiqher incidence of i l l n e s s was observed among the unmedicated sub jec t s i n the e x t e r n a l c o n t r o l group. The d i f f e rence (more than two-fold) i n t h e i n t e n s i t y of t h e development of t h e outbreaks i n these groups was statis- t i c a l l y s i g n i f i c a n t .

4 90

8 0 - I \ I \

70 I \ -

10 15 20 25 31 5 10 15 20 January February

Morbidity p l r 1000/5day$

Control (nu) 276.2 (axtarnel contnl l

Start of

edain ist r r t ion + rmantrd inr

I n # n of af f r c t i r m r r r 2.3

Figure 3 . Morbidity of in f luenza among s u b j e c t s of the experimental (dosed) and c o n t r o l groups dur ing t h e epidemic of in f luenza A2/Hong Kong i n Leningrad, January-February, 1 9 6 9 .

I t is noteworthy t h a t t h e l e v e l s and dura t ions of in f luenza morbidity w e r e d i f f e r e n t i n s tudy popula t ions i n

54

t h e groups r ece iv ing amantadine, placebo, o r no medication ( i n t e r n a l c o n t r o l ) . F igure 4 presen t s t h e morbidi ty curves i n one of t h e popula t ions observed p r i o r t o t h e i n i t i a t i o n of medication i n t h e experimental group (from 10th t o 20th January) and a l s o a f t e r t h e s tar t of t h e amantadine o r placebo program (from 2 1 s t January) . Af t e r t h e drug was s t a r t e d , t h e p a t t e r n s of t h e development of t h e outbreak changed i n these dosed-groups. Morbidity among t h e sub- jects of t h e placebo group cont inued to rise, whi le it dropped i n t h e amantadine group and remained a t t h e l o w e r l e v e l dur ing t h e e n t i r e per iod of t h e outbreak.

Figure 4 . Morbidity of in f luenza A2 among s u b j e c t s of t h r e e subgroups of Populat ion Group N o . 6 i n January- February, 1 9 6 9 .

The du ra t ion and i n t e n s i t y of t h e outbreak i n t h e i n t e r n a l c o n t r o l group no t given medication w e r e q u i t e d i f - f e r e n t from those observed i n t h e previous groups given amantadine or placebo. The rise i n morbidi ty occurred a t an ear l ie r t i m e and reached a higher peak than t h e l e v e l of morbidi ty seen i n t h e placebo group. I t seems l i k e l y t h a t persons from t h i s c o n t r o l group l i v i n g i n more i n t e n s i v e con tac t wi th t h e municipal populat ion w e r e r e spons ib l e f o r t h e in t roduc t ion of t h e in f luenza A 2 v i r u s i n t o t h e i r i n s t i - t u t i o n s . The t o t a l morbidi ty r a t e i n t h e i n t e r n a l c o n t r o l group was two t i m e s a s h igh a s i n t h e placebo group and ex- ceeded t h a t of t h e group p ro tec t ed by amantadine almost 3 times.

5 5

Of s p e c i a l i n t e r e s t is t h e in f luence of prophylac t ic amantadine t rea tment on t h e course of i n f luenza i n those p a t i e n t s who developed d i sease i n s p i t e of dosing.

The c l i n i c a l p i c t u r e s of t h e in f luenza which developed i n those s u b j e c t s rece iv ing amantadine o r placebo w e r e s tud ied by examinations of t h e c l i n i c a l symptoms and of t h e r e s u l t s of s e r o l o g i c a l assay of 400 i n f luenza cases s e l e c t e d a t random. Among them 200 p a t i e n t s rece ived amantadine and 200 placebo (Table 3 ) The s e v e r i t y of t h e symptoms i n t h e amantadine and placebo groups d i f f e r e d so t h a t 56% of t h e s u b j e c t s from t h e amantadine group and 38% of those from t h e placebo group developed mild symptoms (P<O.OOl). Severe symptoms w e r e observed i n 9% of t h e s u b j e c t s i n t h e amanta- d ine group and i n 1 9 % of t h e s u b j e c t s from t h e placebo group (PcO.01).

Table 3 Sever i ty of t h e Symptoms i n Those Subjec ts

Who Becam I11 While on Amantadine HC1 o r Placebo

The f ind ings obtained 'suggest t h a t mi lder forms of i n f luenza developed i n t h e amantadine group compared t o those given placebo. Such symptoms a s c h i l l i n e s s , pa in i n t h e eyes, nausea, malaise , and some c a t a r r h a l symptoms ( r h i n i t i s , wet-cough, pha ryng i t i s ) were s i g n i f i c a n t l y less f requent i n the amantadine group (Table 4 ) . More seve re forms (+++ c o n s t i t u t i o n a l symptoms r a t i n g ) of i n f luenza d i sease were found i n 9% of t h e s u b j e c t s given amantadine and i n 1 9 % of those from t h e placebo group, a s i g n i f i c a n t d i f f e rence (P<O.Ol). While c a t a r r h a l symptoms w e r e l a c k i n g i n 19% of t h e amantadine group, t h i s was ev ident i n only 8% of t h e placebo group (PcO.001).

56

BRWP

Exprrimrntal

Control

t

P

Table 4 Seve r i ty Ratings of t h e Cons t i t u t iona l and Ca ta r rha l

Symptoms i n Those Subjec ts Who Became I11 While on Amantadine H C 1 (Experimental Group) o r Placebo(Contro1 Group)

110. CO(ISTITU1lONAL SWPl OF

CMLS 0 + u 200 30 33 28

200 7 36 38

6.2 0.6 2.1

<0.001 >0.05 (0.05

I S

9

19

2.8

~0.01

CAYARRHAL SYYPTOYS

. H ) o + t ) . H )

19 58 23 - 8 49 35 8

3.3 .l.8 2.6

*O.OOl a0.05 eO.01

Reductions of t h e genera l s igns and symptoms of i l l n e s s , a s w e l l a s of t h e c a t a r r h a l symptoms, a s soc ia t ed wi th pro- p h y l a c t i c amantadine admin i s t r a t ion can be r e l a t e d t o t h e i n i t i a l s e v e r i t y of t h e d i sease (Table 5 ) . Thus, t h e mean dura t ions of f eve r w e r e 2 .6 days i n t h e amantadine group and 3 . 2 days i n t h e placebo group. Mean dura t ions of t h e i n f l u - e n z a l syndrome w e r e 2.5 and 3.4 days and of t h e c a t a r r h a l syndrome 4 . 2 and 5 .7 days r e spec t ive ly f o r t h e drug- and placebo-dosed groups.

Random s e r o l o g i c a l examination of t h e p a t i e n t s wi th c l i n i c a l l y diagnosed in f luenza revea led t h a t a high propor- t i o n of erroneous c l i n i c a l diagnoses w e r e a s soc ia t ed wi th r e s p i r a t o r y i n f e c t i o n s of non-influenza etio1,ogy. 2 9 1 p a t i e n t s s t u d i e d , 1 2 had adenovirus , 9 - para in f luenza , 1 2 - r e sp i r a to ry - synoy t i a l , 3 - i n f luenza type B , 1 - myco- plasma, and 10 - mixed i n f e c t i o n s . Thus, 4 7 (16 .1%) of t h e 2 9 1 ill s u b j e c t s examined w e r e n o t involved with an in f luenza A2 i n f e c t i o n b u t had acute r e s p i r a t o r y d i seases of d i f f e r e n t e t i o l o g i e s which would no t be expected t o respond t o aman- t ad ine . I n t h i s contex t , it must be borne i n mind t h a t ’ t h e prevent ive e f f e c t i v e n e s s of amantadine, and i t s c l i n i c a l e f f e c t i v e n e s s i n the ill s u b j e c t s , w e r e eva lua ted i n popula- t i o n s and p a t i e n t s which inc luded cons iderable numbers of i n s t ances of r e s p i r a t o r y i l l n e s s e s i n which amantadine could n o t obviously prevent o r r e l i e v e symptoms.

Among t h e

57

TYPES

Febrile reaction

Inf luenza syndrome

Catarrhal

Table 5 Durations of t he F e b r i l e React ion, Inf luenza Syndrome

And Ca ta r rha l Symptoms i n t h e Amantadine o r Placebo Groups Related t o t h e Seve r i ty of t h e Disease

MEAN DURATION LDAYS)

OROUPL MILD MWERATE SEVERE DISEASE DISEASE DISEASE ""

Anantadine 20 3.4 3.7 2.6x Placebo 2.7 3.6 3.4 3.2

Amantadine 1.9 3. I 4.1 2.5' Placebo 2.7 3.6 4.6 3.4'

Amantadine 4.2 3.8 5.4 4.2 '

N 0. OF

PATIENTS EXAMINED

BROWS

107 Experimental

137 Control

symptoms I Placebo

I: k 0 0 5

I 5.2 I 5.5 I 7.2 I 5.7'

WITH 4-FOLD YEAN GEOMETRIC VALUE OF

MULTIPLICITY OF RISE IN

$:& Yo ACUTE CONVALESCENT ANTIBODIES

4 5 x 42.1 2.1 192. 4.71 1921

OR YORE MEAN GDMETRIC RISE IN TITERS OFSERUM ANTI - ANTI BODIES BODIES

1.52 : 1:4.0 : 1:26

2.06 58.4 3.71g2- 5.9102: -1:13.9 1 1:60

Sero log ica l f ind ings suggested involvement of i n f luenza A v i r u s i n 42.1% of t h e s u b j e c t s from t h e amantadine and i n 58 .4% from the placebo groups (Table 6 ) . However, a s has been repor ted previous ly ' I , t h e r e was a s i g n i f i c a n t d i f - ference i n t h e i n t e n s i t y of t h e immune responses between t h e groups dosed wi th amantadine o r placebo.

Table 6 S e r o l o g i c a l Findings Among S u b j e c t s of t h e

Experimental (Amantadine) and Cont ro l (Placebo) Groups

58

S i n c e s o m e a u t h o r s have r e p o r t e d amantadine t o produce s i d e e f f e c t s , ' 2 r ' 4 p a r t i c u l a r a t t e n t i o n was g iven t o t h i s area i n t h e c o u r s e of t h e s e s t u d i e s . 1825 s u b j e c t s from t h e amantadine or p lacebo groups who d i d n o t become ill w e r e asked t o f i l l o u t anonymous p a t i e n t check l i s ts . The r e s u l t s t h u s o b t a i n e d are p r e s e n t e d i n Table 7. The t o t a l number of subjects i n t h e amantadine group who r e g i s t e r e d complaints i n excess o f t h e p lacebo group w a s 1 . 9 % . Most r e l i a b l e w e r e t h e compla in ts of v a r i o u s s l e e p d i s t u r b a n c e s and of dyspeps ia d e s c r i b e d by 1 . 1 4 % and an e x c e s s of 1 . 7 % of t h e subjects i n t h e amantadine group r e s p e c t i v e l y . Other s i d e effects w e r e s t a t i s t i c a l l y n o n s i g n i f i c a n t .

Table 7 S i d e E f f e c t s of Amantadine Under Condi t ions of

P r o p h y l a c t i c Adminis t ra t ion w i t h Dai ly D o s e s of 1 0 0 mg

- s l i u E c n

Experimental

Control

lo. Io.occoI- c#mrmra OF:

n.Mm8 SLEEP DETERIpuT~- mm OF w c c n D Y S P E r n MALAISE aUm#*D TOTAL % TOTAL % TOTAL % TOTAL % TOTAL %

2 i 4 ~ ~ 1 0 0 1 0 1 I I t

1313 94 7.1 43 3.28 I5 1.14 27 206 9 058

112 26 5.2 8 I.% - - 14 2.74 4 0.78

DISCUSS I ON

Epidemiologica l and c l i n i c a l o b s e r v a t i o n s of t h e e f f e c - t i v e n e s s of amantadine H C 1 w e r e c a r r i e d o u t i n January- February, 1969 i n Leningrad d u r i n g i n t e n s i v e o u t b r e a k s of i n f l u e n z a due t o i n f l u e n z a A2 v i r u s e s r e l a t e d t o t h e A2/ Hong Kong/68 v a r i a n t s . O f t h e 1 6 4 v i r u s s t r a i n s i s o l a t e d from p a t i e n t s i n t h i s p e r i o d , about h a l f of whom belonged t o t h e p a t i e n t s i n c l u d e d i n t h i s s t u d y , a l l w e r e re la ted t o t h e i n f l u e n z a A2/Hong Kong/68 v i r u s e s accord ing t o t h e i r a n t i - g e n i c and b i o l o g i c a l p r o p e r t i e s . The same e t i o l o g y w a s confirmed by s e r o l o g i c a l examinat ions of p a i r e d h e a t e d sera i n hemagglu t ina t ion i n h i b i t i o n tests which showed a d i s t i n c t p reva lence of a n t i b o d i e s t h a t n e u t r a l i z e d AZ/Hong Kong/1968- 1969 s t r a i n s . T h i s w a s i n c o n t r a s t w i t h a lower l e v e l of an t ibody t o i n f l u e n z a A2/21/65,

D i f f e r m e n in ti n indicated incolums 6 ond 8 ore rtotisticolly sigm'fiwnt ( w i t r & i d w e low1 of 5% ond 1% respectively)

59

The s i g n i f i c a n t xeduction of morbidi ty rates among persons given a d a i l y dose of 1 0 0 mg of amantadine when compared wi th t h e placebo group, as w e l l a s wi th a d d i t i o n a l i n t e r n a l and e x t e r n a l c o n t r o l groups, showed t h a t t h e causa- t i v e v i ruses r e l a t e d t o t h e A2/Hong Kong/68 v a r i a n t s were s e n s i t i v e to amantadine n o t only i n t h e labora tory o r i n volunteers b u t a l s o t h a t t h e medication w a s e f f e c t i v e aga ins t t h e n a t u r a l d i sease caused by t h i s v i rus . The e f f e c t of t h e amantadine prevent ive a c t i o n was s t a t i s t i c a l l y d i s t i n c t i n analyses involv ing a l l 6 s tudy popula t ions and became ev iden t immediately a f t e r o r a l adminis t ra t ion s t a r t e d .

The reduct ion i n t h e incidence of i n f luenza i l l n e s s observed i n a l l s i x groups determined i n comparisons of t h e amantadine and placebo groups became even more pro- nounced when e f f ec t iveness is judged i n comparisons of t h e amantadine-dosed groups wi th t h e i n t e r n a l o r e x t e r n a l con- t r o l s . w e r e involved side-by-side i n t h e var ious s tudy populat ions. The observed lesser incidence i n the placebo-dosed ind i - v idua l s than i n t h e i n t e r n a l con t ro l s and i n p a r t i c u l a r , i n t h e e x t e r n a l c o n t r o l s , may be t h e r e s u l t of a decrease i n the amount of environmental v i r u s conten t a s a r e s u l t of a decrease i n t h e amount of environmental v i r u s conten t as a r e s u l t of dosing wi th the drug. This degree of epidemi- o log ic b e n e f i t i s s u f f i c i e n t t o j u s t i f y t h e mass amantadine use f o r e f f e c t i v e c o n t r o l of in f luenza A-type epidemics.

The placebo-dosed and amantadine-dosed s tudy s u b j e c t s

The pronounced rise of amantadine e f f e c t i v e n e s s i n people wi th p reex i s t ing an t ibod ie s demonstrated i n t h e a r t i f i c i a l l y induced inf luenza d i sease i n volunteers has been confirmed by t h e au thors i n observa t ions on previous ly vaccinated groups r ece iv ing amantadine dur ing t h e 1969 out- break (da t a not included i n t h i s pape r ) . These d a t a form t h e bases f o r recommending a combined prevent ive program which would involve t h e mass immunization of a d u l t and ch i ld ren populat ions with l i v e o r k i l l e d in f luenza vaccines i n September-November and subsequent enhancement of t h e prevent ive e f f e c t by use of amantadine i n t h e same groups a t t h e t i m e of outbreaks due t o in f luenza A-type v i ruses .

Considering t h e importance of continuous d a i l y appl i - ca t ion of t h e drug f o r i t s b e s t e f f i c a c y , w e suggest t h a t it would be e s p e c i a l l y d e s i r a b l e t o s t i m u l a t e t h e gene ra l p r a c t i c a l use of amantadine among high in f luenza - r i sk groups (o ld people, p a t i e n t s wi th card iovascular d i s tu rb - ances, and preschool c h i l d r e n ) , a s w e l l a s i n o t h e r popu- l a t i o n s where the r egu la r admin i s t r a t ion of amantadine can be supervised (army, schools , hea l th personnel , e tc . ) .

60

Incorporation of amantadine in fruit juices and other drinks can be recommended as a method to assure its regular use.

CONCLUSIONS

viruses related to influenza A2/Hong Kong/1968 variants the prophylactic effectiveness of amantadine HC1 was studiea under conditions of double-blind, inert pLacebo-controlled tests involving adults in six similar institutions. In all, 10,053 persons participated in the study.

1) During an epidemic of influenza due to influenza

2) According to the summarized clinical findings the index of amantadine effectiveness in the total group was 1.7. When only those subjects are considered who received aman- tadine regularly, the index of effectiveness based on clini- cal diagnosis was increased to 1.95. When the clinical diagnoses are corrected by serological confirmatory tests, the index of effectiveness rises to 2.15. A comparison of the drug-treated group with the nonmedicated internal con- trol group showed an index of effectiveness of 5.32.

3) Preventive treatment with amantadine resulted in the reduction of influenza A2 morbidity not only in the drug group, but also in the side-by-side placebo-dosed controls.

4) Clinical examination of patients -continuously receiving amantadine or placebo beginning prior to the influenza attack showed that regular administration of amantadine at a daily dose of 100 mg reduced not only the incidence of influenza infection, but also the severity and duration of symptoms in those subjects who became ill.

5) Administration of amantadine to healthy young subjects at a daily dose of 100 mg after a meal was associ- ated with a 1.14% increase in the number of complaints of various sleep disturbances with no interference with work- ing capacity. This quite insignificant difference in the amantadine group cannot be considered a contraindication to the wide general application of the drug.

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