Cleocin (clindamycin)

Clindamycin carries a boxed warning for Clostridioides difficile infection, which can range from mild diarrhea to fatal colitis^[1]. The label says this diarrhea has been reported more than 2 months after the last dose^[1]. Because of this risk, the label says clindamycin should be reserved for serious infections where less toxic antibiotics are inappropriate^[1].

The label also warns of severe allergic reactions, including anaphylaxis and reduced blood flow to the heart (myocardial ischemia) as part of an allergic reaction^[1][2]. Severe skin reactions such as Stevens-Johnson syndrome, toxic epidermal necrolysis and DRESS have been reported, some fatal^[2]. Acute kidney injury can occur, so the injection label suggests kidney monitoring in people at higher risk^[2]. The most frequently reported reaction is a mild to moderate measles-like rash^[1]. Nausea, vomiting, abdominal pain and a metallic taste have also been reported^[1]. Ulcers of the esophagus have been reported, mostly when capsules are taken lying down or with little water^[1].

In the babesiosis trial, the most common side effects with clindamycin plus quinine were ringing in the ears (39%), diarrhea (33%) and reduced hearing (28%)^[7]. Ringing in the ears and hearing loss are part of cinchonism, a group of symptoms the quinine label says affects almost all people taking quinine^[8]. Quinine also has its own boxed warning about serious blood reactions, written for its unapproved use in leg cramps^[8].

In CDC's adult dosing table (adapted from the 2020 IDSA guideline), outpatients take clindamycin 600mg by mouth 3 times a day plus quinine 650mg by mouth 3 times a day^[6]. Hospitalized adults with severe disease get clindamycin 600mg by IV 4 times a day with the same oral quinine dose^[6]. Once symptoms improve, patients switch to all oral doses to finish 7 to 10 days in total^[6]. Highly immunocompromised patients may need 6 weeks or more^[5].

For severe Babesia microti infection, IDSA reserves IV clindamycin plus oral quinine for patients who do not respond to atovaquone plus azithromycin^[5]. IDSA gives the reason that quinine often causes side effects^[5]. IDSA also notes that the rarer species Babesia duncani and Babesia divergens have usually been treated with IV clindamycin plus oral quinine^[5]. CDC says clindamycin plus quinine is generally the recommended combination for symptomatic babesiosis in pregnancy^[6].

The Cleocin HCl label says to take capsules with a full glass of water and at least 30 minutes before lying down^[1]. The label says this lowers the risk of irritating the esophagus (food pipe)^[1].

Some Lyme-literate physicians include clindamycin among rotating treatments for babesiosis that keeps returning in people with chronic Lyme symptoms.

Who describes it: Richard Horowitz and colleagues report a patient with relapsing Babesia symptoms who received clindamycin with atovaquone as part of a longer treatment plan^[11].

Evidence: this comes from a case report and chart reviews, not randomized trials^[11][10].

Mainstream guidance: the 2020 IDSA guideline lists clindamycin plus quinine as the alternative when atovaquone plus azithromycin cannot be used^[5].

Source: Horowitz, Fallon and Freeman, Microorganisms 2024; Horowitz and Freeman, Healthcare 2018; IDSA 2020.

Clindamycin is not FDA-approved for babesiosis, but the 2020 IDSA guideline lists clindamycin plus quinine as the alternative to atovaquone plus azithromycin^[5][1].

When it is used: It is used when that preferred regimen cannot be given because of side effects, availability or cost^[5].

Source: IDSA guideline, 2020; Cleocin HCl FDA label, Apr 2026

CDC's adult dosing table, adapted from the 2020 IDSA guideline, pairs clindamycin with oral quinine for babesiosis^[6].

Hospitalized adults: Hospitalized adults with severe babesiosis get clindamycin 600mg by IV 4 times a day^[6].

Outpatients: Outpatients get 600mg by mouth 3 times a day, and both groups take oral quinine 650mg 3 times a day^[6].

Length of treatment: Once symptoms improve, the table moves patients to all oral doses to finish 7 to 10 days in total^[6]. Highly immunocompromised patients may need 6 weeks or more^[5].

Source: CDC, Clinical Care of Babesiosis; IDSA guideline, 2020

Clindamycin carries a boxed warning for Clostridioides difficile-associated diarrhea, which can range from mild diarrhea to fatal colitis^[1].

Boxed warning details: This diarrhea can start more than 2 months after the last dose^[1]. The label says clindamycin should be reserved for serious infections when less toxic antibiotics are inappropriate^[1].

Other serious risks: Severe allergic reactions, kidney injury and serious skin reactions such as Stevens-Johnson syndrome, toxic epidermal necrolysis (TEN) and DRESS can also occur^[1][2].

Other side effects: Nausea, vomiting, abdominal pain and a measles-like rash have also been reported^[1]. With quinine, cinchonism is common, and in the babesiosis trial 39% had ringing in the ears and 28% had reduced hearing^[7][8].

Source: Cleocin HCl FDA label, Apr 2026; Cleocin Phosphate FDA label, Jul 2026; NEJM, 2000; Quinine sulfate FDA label, Oct 2025

In bacteria, clindamycin blocks protein production at the 50S ribosome^[1].

In Babesia: Babesia parasites carry a bacteria-like compartment called the apicoplast^[9].

Lab evidence: A lab study found clindamycin and other apicoplast-targeting drugs slowed Babesia growth^[9].

Source: Cleocin HCl FDA label, Apr 2026; Antimicrob Agents Chemother, 2012