Bidvest said in a statement it now holds 32.03 percent of Adcock, South Africa's second-largest pharmaceutical company, and confirming a Reuters’ report it had bought the bulk of the record 39 million Adcock shares traded on Thursday.
Chilean firm CFR Pharmaceuticals has offered 12.8 billion rand in cash and shares for Adcock a deal that requires approval from shareholders with 75 percent of Adcock at a meeting next month.
Shares of Adcock fell 1.4 percent to 69 rand at 0826 GMT, just below Bidvest's cash offer of 70 rand a share.
Before Thursday's buying spree, Bidvest had held around 9 percent of Adcock.
The 39 million shares traded on Thursday represented a record since Adcock's listing in 2008 and far outstrips last year's daily average of under 650,000 shares, according to Thomson Reuters data.
Bidvest, which first tried for control of Adcock in March, has gone to shareholders with a cash offer for 34.5 percent of Adcock. That offer expires next week.
Adcock Ingram is due to hold its annual general meeting later on Friday.