Jhoots Pharmacy in Kingswinford High Street left customers in shock when it changed the price of a pack of 32 paracetamol from its normal £1.20 per packet to £8.
It has also been reported Calpol was being sold for £10 per bottle.
The prices have now been returned to normal with the pharmacy chain blaming "an erroneous communication" for "pricing disparities at a small number of branches".
However, when Ryan Mather called to check the price at the branch yesterday, the worker on the end of the line said head office had changed the prices due to increased costs from wholesalers.
Mr Mather, 37, decided to investigate after seeing reports on social media which he struggled to believe were true.
He called the pharmacy, who said they had plenty of stock in at the new price, but when he arrived at the pharmacy in person the price had changed.
Mr Mather said: "I phoned and she admitted it was £8, so I went into the store and recorded it on video and she immediately dropped the price to £1.30.
"I was in complete dismay by what I was told.
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"Taking advantage of people in this situation with medicines is not justified in any way.
"Whether it's head office or the pharmacy, they shouldn't be doing it.
"Some people might get paid £8 an hour and get through a box in two days. It's a lot of money.
"Some people aren't in the situation where they can afford it."
A Jhoots branch in Birmingham has also come under fire after bottles of 200ml liquid paracetamol appeared for sale for about treble the average standard price.
Birmingham city councillor Majid Mahmood said he had had five people from his ward tearfully ringing him up about the rises on Wednesday.
His Bromford and Hodge Hill ward sits in one of the most deprived constituencies in England, with a 2018 study commissioned by the End Child Poverty Coalition finding more than half of children grew up in poverty.
Mr Mahmood posted a photograph on Twitter, taken in the pharmacy, showing the price of 100ml of Calpol as £9.99 and a 200ml bottle listed for £19.99.
Jhoots Pharmacy has since confirmed that the prices have been corrected and appeared to blame individual branches - despite local workers their saying the prices had been set by head office.
A spokesman for the pharmacy, which has 12 branches across the Black Country and Staffordshire, said: "It has been brought to our attention that pricing disparities occurred yesterday at a small number of our branches.
"We have acted immediately and conducted a thorough investigation into this matter and have found that following an erroneous communication, price increases were made at branch level.
"In order to rectify the issue we will make full refunds to our customers affected by this and have taken all appropriate action to ensure that this does not happen again.
"We will continue to maintain out focus of serving our customers to the best of our ability during a very busy and challenging period."
The Kingswinford branch did not want to comment.
Several independent convenience stores across the Black Country have also been criticised for increasing the cost of hand sanitisers, toilet roll and painkillers.
The National Pharmacy Association said that pharmacies were facing fluctuating wholesale prices on medicines and other supplies such as hygiene products.
On Wednesday, the Competitions and Markets Authority (CMA) said it was taking "an extremely high number of calls" from the public about sales and pricing during the Covid-19 outbreak.
Earlier this month, the CMA warned retailers they must not try to "take advantage of people" concerned about the outbreak of coronavirus.
Officials at the competition watchdog also said they would take strict action and that anyone trying to inflate prices could be fined under competition laws.
Jhoots Pharmacy, based in Walsall, also has branches in Thornley Street, Wolverhampton; Tettenhall Road, Wolverhampton; Birmingham Road, Great Barr; Pinfold Street, Darlaston; Milking Bank, Dudley; Halesowen Road, Netherton; Dimbles Lane, Lichfield; High Street, Cradley Heath; Lichfield Road, Burntwood; Cottage Street, Brierley Hill; Rowley Regis and a number of branches in Birmingham.