<PAGE>   1

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
   
                                    Form 10-Q/A
    

(Mark One)

[X]      QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
         SECURITIES EXCHANGE ACT OF 1934

         For the quarterly period ended July 31, 1997

[  ]     TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
         SECURITIES EXCHANGE ACT OF 1934

         For the transition period from ________________ to ________________

                          Commission File Number 1-8366
                                                 -------

                         POLYDEX PHARMACEUTICALS LIMITED
--------------------------------------------------------------------------------
             (Exact name of registrant as specified in its charter)

  Commonwealth of the Bahamas                                None
-------------------------------------                --------------------------
(State or other jurisdiction of                           (I.R.S. Employer
incorporation or organization)                            Identification No.)

             421 Comstock Road, Scarborough, Ontario, Canada M1L 2H5
--------------------------------------------------------------------------------
                    (Address of principal executive offices)

Registrant's telephone number, including area code (416) 755-2231
                                                   ---------------

         Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.

                           Yes   X      No
                               -----       -----

         Indicate the number of shares outstanding of each of the issuer's
classes of common shares, as of the latest practicable date.

Common Shares, $.0167 Par Value                     2,994,816
-------------------------------                --------------------
(Title of Class)                          (Outstanding at September 5, 1997)


                                   

<PAGE>   2
   
The Registrant hereby amends its quarterly report for the quarterly period
ended July 31, 1997, for the sole purpose of (i) adding, in Part I, Item 2 and
Part II, Item 2(c), disclosures regarding two unrelated transactions between
the Registrant and an unaffiliated third person and (ii) amending Part I, Item
1 and Exhibit 27 to reflect such transactions.
    




                                     -2-
<PAGE>   3



                         PART I - FINANCIAL INFORMATION
                         ------------------------------



Item 1.   Consolidated Financial Statements.


POLYDEX PHARMACEUTICALS LIMITED AND
SUBSIDIARIES


Consolidated Balance Sheets
(Expressed in United States dollars)

   
<TABLE>
<CAPTION>
                                                                         (Unaudited)
                                                                             July 31         January 31
                                                                                1997               1997
--------------------------------------------------------------------------------------------------------

<S>                                                                <C>                 <C>             
Assets

Current Assets:
       Cash                                                        $       1,443,352   $        603,491
       Trade accounts receivable, net of allowance                           936,152          1,107,829

       Inventories:
            Finished goods                                                   808,083            656,039
            Work in process                                                   57,559             89,640
            Raw materials                                                    534,765            533,601
            --------------------------------------------------------------------------------------------
                                                                           1,400,407          1,279,280

       Prepaid expenses and other current assets                              57,572             63,312
       -------------------------------------------------------------------------------------------------
                                                                           3,837,483          3,053,912

Property, plant and equipment, at cost
       Land and buildings                                                  2,814,065          2,796,935
       Machinery and equipment                                             5,104,066          5,077,720
       -------------------------------------------------------------------------------------------------
                                                                           7,918,131          7,874,655
       Less allowances for depreciation and amortization                  (4,139,957)        (4,017,353)
       -------------------------------------------------------------------------------------------------
                                                                           3,778,174          3,857,302

Patents and animal drug applications at cost, net of
       accumulated amortization                                              878,860            877,311
Due from Novadex Inc.                                                        770,818            765,209
Other assets                                                                  54,667             73,783

--------------------------------------------------------------------------------------------------------

                                                                   $       9,319,999   $      8,627,517
--------------------------------------------------------------------------------------------------------
</TABLE>
    


                                      -3-
<PAGE>   4


   
<TABLE>
<CAPTION>
                                                                         (Unaudited)
                                                                             July 31         January 31
                                                                                1997               1997
--------------------------------------------------------------------------------------------------------

<S>                                                                <C>                 <C>             
LIABILITIES AND SHAREHOLDERS' EQUITY

Current liabilities:
       Accounts payable and accrued liabilities                    $       1,356,226   $      1,511,698
       Current portion of long-term debt                                      58,487             60,185
       -------------------------------------------------------------------------------------------------
                                                                           1,414,713          1,571,883

Long-term debt                                                               493,104            524,656

Due to shareholders                                                          629,060            605,475

Due to affiliated companies                                                  425,420            425,420

Deferred gain                                                                675,221            776,564

Minority interest                                                               -                22,791

Shareholders' equity:
       Capital stock:
            Authorized:
                 100,000 A preferred shares of $0.10 each 
                 899,400 B preferred shares of $0.0167 each 
                 4,000,000 common shares of $0.0167 each
            Issued and outstanding:
                 899,400 B preferred shares                                   15,010             15,010
                 2,994,816 common shares (January 31,
                      1997 - 2,825,182) of which 8,240 are
                      held in treasury                                        49,786             46,959
       Contributed surplus                                                23,823,522         22,733,319
       Deficit                                                           (17,629,923)       (17,559,330)
       Currency translation adjustments                                     (575,914)          (535,230)
       -------------------------------------------------------------------------------------------------
                                                                           5,682,481          4,700,728

--------------------------------------------------------------------------------------------------------

                                                                   $       9,319,999   $      8,627,517
--------------------------------------------------------------------------------------------------------
</TABLE>
    

       See accompanying note to financial statements



                                      -4-
<PAGE>   5

POLYDEX PHARMACEUTICALS LIMITED AND
SUBSIDIARIES

Consolidated Statement of Operations (Unaudited)

(Expressed in United States dollars)


<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------------
                                                                                             (Restated - See Note)
                                                                                      ------------------------------------
                                                 Quarter Ended       Year to Date      Quarter Ended       Year to Date
                                                       July 31            July 31            July 31            July 31
                                                          1997               1997               1996               1996
--------------------------------------------------------------------------------------------------------------------------

<S>                                           <C>                <C>                <C>                <C>               
Sales                                         $      2,343,259   $      4,579,594   $      1,902,118   $      4,149,078
                                                                                                       
Cost of products sold, exclusive of                                                                    
      depreciation reported below                    1,660,309          3,245,214          1,477,652          3,154,405
------------------------------------------------------------------------------------------------------------------------
                                                       682,950          1,334,380            424,466            994,673
                                                                                                       
Expenses:                                                                                              
      Selling and promotion                             93,327            160,985             39,598             67,372
      General and administrative                       449,755            839,722            442,846            759,589
      Depreciation and amortization                    151,093            295,685            157,026            300,237
      Interest expense                                  29,017             58,035             38,657             77,826
      Research and development                          33,197             71,568             24,521             85,355
      ------------------------------------------------------------------------------------------------------------------
                                                       756,389          1,425,995            702,648          1,290,379
------------------------------------------------------------------------------------------------------------------------
                                                                                                       
Profit (loss) from operations                          (73,439)           (91,615)          (278,182)          (295,706)
                                                                                                       
Other income (expenses):                                                                               
      Interest and other                                 8,842             19,840             23,405             29,247
------------------------------------------------------------------------------------------------------------------------
                                                                                                       
Profit (loss) before the undernoted                    (64,597)           (71,775)          (254,777)          (266,459)
                                                                                                       
Provision for income taxes                                   -                  -                  -                  -
                                                                                                       
Minority interest in loss                                  480              1,182                  -                  -
------------------------------------------------------------------------------------------------------------------------
                                                                                                       
Profit (loss) for the period                  $        (64,117)  $        (70,593)  $       (254,777)  $       (266,459)
------------------------------------------------------------------------------------------------------------------------
                                                                                                       
                                                                                                       
Per share information, as restated (see                                                                
note below):                                                                                           
      Profit (loss) per common share:                                                                  
              For the period                  $          (0.02)  $          (0.02)  $          (0.09)  $          (0.09)
                                                                                                       
------------------------------------------------------------------------------------------------------------------------
</TABLE>

      Note to interim financial statements:
              On June 19, 1997, the shareholders of the Company passed a
              resolution authorizing a one-for-ten reverse share split. All
              comparative amounts have been restated to reflect the impact of
              this reverse share split on a retroactive basis.

              Subsequent to the release of the consolidated financial statements
              for the three and six months ended July 31, 1996, management
              re-examined the appropriate accounting for the gain on the
              disposition of shares in Novatek International Inc. taking into
              account the potential risks associated with a lawsuit filed
              against the Company. Management determined that it would be more
              appropriate to defer any gain associated with this disposition
              pending resolution of the lawsuit. This change has been accounted
              for on a retroactive basis in these consolidated financial
              statements.



                                      -5-
<PAGE>   6

POLYDEX PHARMACEUTICALS LIMITED AND
SUBSIDIARIES

Consolidated Statement of Shareholders' Equity (Unaudited)

(Expressed in United States dollars)

   
<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------
                                                                                          (Restated -
                                                                                             See Note)
                                                                     Year to Date        Year to Date
                                                                          July 31             July 31
                                                                             1997                1996
------------------------------------------------------------------------------------------------------

<S>                                                              <C>                <C>              
Preferred Shares:
         Balance, beginning of period                            $         15,010   $          15,010
         Private placement of preferred shares                                  -                   -
         ---------------------------------------------------------------------------------------------

         Balance, end of period                                  $         15,010   $          15,010
------------------------------------------------------------------------------------------------------

Common Shares:
         Balance, beginning of period                            $         46,959   $          46,625
         Exercise of options                                                   40                   -
         Private placement of common shares                                 2,787                 334
         ---------------------------------------------------------------------------------------------

         Balance, end of period                                  $         49,786   $          46,959
------------------------------------------------------------------------------------------------------

Contributed Surplus:
         Balance, beginning of period                            $     22,733,319   $      22,583,653
         Exercise of options                                               17,960                   -
         Private placement of common shares                             1,072,243             149,666
         ---------------------------------------------------------------------------------------------

         Balance, end of period                                  $     23,823,522   $      22,733,319
------------------------------------------------------------------------------------------------------

Deficit:
         Balance, beginning of period                            $    (17,559,330)  $     (17,681,720)
         Net income (loss) for the period                                 (70,593)           (266,459)
         ---------------------------------------------------------------------------------------------

         Balance, end of period                                  $    (17,629,923)  $     (17,948,179)
------------------------------------------------------------------------------------------------------

Currency translation adjustments:
         Balance, beginning of period                            $       (535,230)  $        (522,851)
         Currency translation adjustment for the period                   (40,684)              2,285
         ---------------------------------------------------------------------------------------------

         Balance, end of period                                  $       (575,914)  $        (520,566)
------------------------------------------------------------------------------------------------------
</TABLE>
    



                                      -6-
<PAGE>   7

POLYDEX PHARMACEUTICALS LIMITED AND
SUBSIDIARIES

Consolidated Statement of Cash Flows (Unaudited)

(Expressed in United States dollars)

   
<TABLE>
<CAPTION>
                                                                      Year to Date          Year to Date
                                                                           July 31               July 31
                                                                              1997                  1996
----------------------------------------------------------------------------------------------------------

<S>                                                               <C>                  <C>
Cash provided by (used in):

Operating activities:
      Profit (loss) for the period                                $        (70,593)    $       (266,459)
      Add (deduct) items not affecting cash:                                           
            Depreciation and amortization                                  295,685              300,237
            Legal expenses relating to deferred gain                      (101,343)                   -
            Minority interest                                               (1,182)                   -
            Expenses paid by issuance of common shares                      18,000                    -
      Change in non-cash operating working capital                         (93,796)            (101,465)
      --------------------------------------------------------------------------------------------------
                                                                            46,771              (67,687)
      --------------------------------------------------------------------------------------------------
                                                                                       
Investing activities:                                                                  
      Additions to property, plant and equipment                          (162,020)            (175,462)
      Proceeds from sale of investment in                                              
            Novatek International Inc.                                           -            1,278,412
      Additions to patents and animal drug applications                          -               (1,877)
      --------------------------------------------------------------------------------------------------
                                                                          (162,020)           1,101,073
      --------------------------------------------------------------------------------------------------
                                                                                       
Financing activities:                                                                  
      Private placement of common shares                                 1,000,000                    -
      Repayment of long-term debt                                          (33,250)             (39,042)
      Advances from (repayment to) shareholders                             23,585               85,704
      Advances from (repayment to) Novadex Inc.                             (5,609)                   -
      --------------------------------------------------------------------------------------------------
                                                                           984,726               46,662
                                                                                       
      Effect of exchange rate changes on cash                              (29,616)             (13,704)
--------------------------------------------------------------------------------------------------------
                                                                                       
Increase (decrease) in cash position                                       839,861            1,066,344
                                                                                       
Cash position, beginning of period                                         603,491               12,321
                                                                                       
--------------------------------------------------------------------------------------------------------
Cash position, end of period                                      $      1,443,352     $      1,078,665
--------------------------------------------------------------------------------------------------------
</TABLE>
    





                                      -7-
<PAGE>   8



Item 2.   Management's Discussion and Analysis of Financial Condition and 
          Results of Operations.


(A) RESULTS OF OPERATIONS

During the fiscal quarter ended July 31, 1997, the Registrant's pre-tax profit
from operations prior to research and development, interest charges,
depreciation and interest and other income amounted to $139,868, as compared to
a similarly calculated pre-tax loss of $57,978 for the same period last year.
This improvement in results is due to an increase in such profits at Dextran
Products Limited ("Dextran") of $98,930 and at Veterinary Laboratories Inc.
("Vet Labs") of $162,346, partially offset by increased expenses at the
corporate head office of $58,276. The Registrant's year to date pre-tax profit
from operations prior to research and development, interest charges,
depreciation and interest and other income amounted to $333,673, as compared to
a similarly calculated amount of $167,712 for last year. Consistent with the
quarterly changes, both Dextran and Vet Labs have achieved year to date
increases in such profits, while corporate head office expenses have increased.

Sales volume this quarter increased from the same period last year by $441,141.
This increase in sales volume is entirely attributable to sales at Vet Labs, as
the volume at Dextran was consistent with the same quarter the prior year. Sales
at Vet Labs increased relative to the same period last year as last year's sales
volumes in the second quarter were very low due to the severe drought
experienced by the midwestern region of the United States and the price war on
Iron Dextran injectibles. On a year to date basis, both Dextran and Vet Labs
have sales volume increases.

Gross margins increased from 22% in the second quarter last year to 29% this
quarter. Dextran's quarter over quarter gross margin increased from 37% to 45%
while Vet Labs' gross margin increased from -1% to 12%. The margin increase at
Dextran is due to a decline in the average Canadian dollar exchange rate, labour
efficiencies achieved and sales mix. The increase in margin at Vet Labs is
attributable to the return to normal sales volumes this year. The severe drop in
sales in the second quarter last year resulted in Vet Labs not covering their
fixed manufacturing costs. This trend in improved margin has carried over from
the first quarter.

Selling and promotion expenses in the quarter increased by $53,729 as compared
to the second quarter last year due to contracting the services of a marketing
company to begin promotion of new products. This continues the trend from first
quarter.



                                      -8-
<PAGE>   9


General and administrative expenses in the quarter are comparable to the same
period last year. The year to date increase is mainly a result of one-time
expenses incurred in the first quarter.

Interest expenses have decreased by $9,640 compared to the same quarter last
year due in part to the refinancing of the mortgage payable on Dextran's plant
in the amount of $167,000 which occurred on January 31, 1997. This continues the
trend from first quarter.

Research and development, in conjunction with the University of British
Columbia, involving the treatment of cystic fibrosis using a form of Dextran is
continuing. A clinical trial is expected to start in 1998. Research and
development, by the Rush Institute of the University of Chicago, relating to
Cellulose Sulphate gel is progressing. Clinical trials are expected to commence
in 1998.

Comparative amounts at July 31, 1996 have been restated to defer the gain on the
disposition of shares in Novatek International Inc. pending resolution of the
lawsuit filed against the Company. This change has been accounted for on a
retroactive basis.

Operating results for the three and six months ended July 31, 1997 are not
necessarily indicative of the results that may be expected for the year ended
January 31, 1998. For further information, refer to the consolidated statements
and footnotes thereto included in the Registrant's annual report on Form 10-K
for the year ended January 31, 1997.



(B) LIQUIDITY AND CAPITAL RESOURCES

The Registrant has generated a year to date positive cash flow from operations
of $46,771 compared to the prior year negative cash flow from operations of
$67,687, which is primarily attributable to the improved year to date results.

Accounts receivable at Dextran decreased from $563,041 at the previous year end
to $527,460, while Vet Labs' receivable balance decreased from $560,139 at the
previous year end to $408,692. The decrease in the receivable balances are
primarily due to the collection of year end accounts receivable.

The inventory levels have increased by $121,127 from the previous year end. The
majority of this increase is at Dextran to provide as contingency in case there
are any production interruptions during the anticipated plant refurbishment
later this year.

During July, 1997, the Chairman, Dr. Alec Keith, purchased 159,680 shares at
$6.2625 per share for aggregate proceeds of $1,000,000 through a private
placement. Management intends to use these share proceeds to fund the
anticipated expansion and refurbishment of the plant and equipment at Dextran.

   
During July 1997, the Registrant bought out the 10% minority interest in its
subsidiary, Novadex International Inc.  The Registrant issued 7,500 of its
common shares as consideration for this purchase.  The shares were valued at
$10 per share.  Since this was a non-cash transaction, it has not been
reflected in the statement of cash flows.
    





                                      -9-
<PAGE>   10


Positive operational cash flows are expected to continue in the future, but
should the need for further cash infusions arise, the Registrant believes that
continued loans and/or capital contributions from principal shareholders will
meet these requirements.



The accompanying unaudited condensed consolidated financial statements have been
prepared in accordance with generally accepted accounting principles for interim
financial information and with the instructions to Form 10-Q and Article 10 of
Regulation S-X. Accordingly, they do not include all of the information and
footnotes required by generally accepted accounting principles for complete
financial statements. In the opinion of management, all adjustments (consisting
of normally recurring accruals) considered necessary for a fair presentation
have been included.


                                      -10-
<PAGE>   11
                          PART II - OTHER INFORMATION
                          ---------------------------

Item 2. Changes in Securities.

   
    

         (c) On July 2, 1997, the Company sold 159,680 Common Shares to Dr. Alec
Keith, Chairman of the Board, for $1,000,000 in cash in a private placement. The
shares were sold pursuant to a subscription agreement (the "Subscription
Agreement") between Dr. Keith and the Company. Such shares were issued in
reliance upon the exemption from registration provided in Section 4(2) of the
Securities Act of 1933, as amended (the "Securities Act"). Pursuant to the
Subscription Agreement, Dr. Keith represented his intention to acquire the
shares for investment only and not with a view to or for sale in connection with
any distribution thereof, and appropriate legends were affixed to the share
certificates issued in such transaction.

   
         On July 14, 1997, the Company issued 2,404 Common Shares to Mr. Martin
Lipper, a non-affiliate, pursuant to the exercise of stock options.  Such
options were granted outside of any plan and had an exercise price of $7.50 per
share.  The Company did not receive a cash payment from Mr. Lipper in   
connection with the exercise of the options.  Instead, the shares were issued   
in exchange for past services rendered by Mr. Lipper, valued at $18,000.        
On that same date, in an unrelated transaction, the Company also issued 7,500   
Common Shares to Mr. Lipper in exchange for the 10% minority interest he held   
in a subsidiary of Registrant, Novadex International Inc. ("Novadex"). The      
Company now owns 100% of Novadex. All shares issued to Mr. Lipper were issued   
in reliance upon the exemption from registration provided in Section 4(2) of
the Securities Act.  Appropriate legends were affixed to the share certificates
issued in both transactions. 


    



                                      -11-
<PAGE>   12



                                   SIGNATURES


         Pursuant to the requirements of the Securities Exchange Act of 1934,
the Registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

   
Date:    December 15, 1997
    

                        POLYDEX PHARMACEUTICALS LIMITED
                        (Registrant)

                        By  /s/ George G. Usher
                           ------------------------------------------
                                George G. Usher, President and Chief
                                Executive Officer
                                (Principal Executive Officer)

   
    



                                      -12-