Clindamycin: when it is used, bowel risks and what to report

Clindamycin is an antibiotic from the lincosamide group. It is available as capsules, as a solution for injection or infusion given in hospital, and in topical forms such as gels and lotions used for acne. This page focuses on the oral and injected forms used to treat infections inside the body.

The manufacturer leaflet for the injection describes it as used to kill certain serious bacterial infections and says people will usually be in hospital when they receive it. The Dalacin C capsule product information describes it as an antibacterial for serious infections caused by susceptible gram-positive organisms such as staphylococci, streptococci and pneumococci, and for serious infections caused by susceptible anaerobic bacteria.

That wording matters. The product information says clindamycin should only be used in the treatment of serious infections, and that the prescriber should bear in mind the type of infection and the potential hazard of the diarrhoea which may develop.

The NHS explains that there are hundreds of antibiotics, most of them classified into six groups, and that antibiotics given by drip or injection are used for more serious infections. Clindamycin is licensed for serious infections caused by susceptible bacteria.

The injection leaflet says clindamycin does not get into the brain, so another antibiotic may be needed for infections in and around the brain. The leaflet also lists allergy to lincomycin, a related antibiotic, as a reason not to be given it.

Because it is chosen with care, ask the prescriber what infection is being treated, why clindamycin was selected, and how long the course will last. Finish the course unless a doctor tells you to stop, but do not carry on if severe diarrhoea develops without speaking to a clinician first.

The key safety message for clindamycin is about the bowel. The injection leaflet says to tell your doctor immediately if you develop severe, persistent or bloody diarrhoea, which may be associated with stomach pain or fever, and notes it may be a sign of serious bowel inflammation that can occur even two to three weeks after antibiotics.

The Dalacin C product information explains the mechanism. Treatment with antibacterial agents alters the normal bacteria of the colon, leading to overgrowth of Clostridioides difficile, which produces toxins that cause colitis. It says the appearance of marked diarrhoea should be regarded as an indication to stop the medicine immediately, and that the condition can range from mild watery diarrhoea to severe colitis. It also says cases have been reported over two months after antibiotics, and that it tends to follow a more severe course in older or debilitated patients.

The NHS C. diff page says you are more likely to get an infection if you are over 65, have recently taken antibiotics, have been in hospital or a care home for a long time, have a weakened immune system or take stomach acid medicines. It advises asking for an urgent GP appointment or help from NHS 111 if you have diarrhoea and are taking or have recently taken antibiotics, have bloody diarrhoea or bleeding from the bottom, or have diarrhoea for more than 7 days.

Treatment for C. diff involves stopping the antibiotic if possible and taking a 10-day course of another antibiotic that can treat the infection, which NICE guideline NG199 lists as oral vancomycin first line. Drinking plenty of fluids matters, and the NHS asks people to stay at home until at least 48 hours after diarrhoea stops and to wash hands with soap and water, because hand sanitiser does not kill C. diff.

The injection leaflet names the contraceptive pill: it may not work, so you should use additional contraception such as a condom during treatment and for 7 days after the last dose. It also lists erythromycin, which may reduce how well both antibiotics work together, warfarin and similar blood thinners, which can increase bleeding and need more frequent clotting tests, and rifampicin, which may affect how clindamycin works.

The Dalacin C product information adds that clindamycin has neuromuscular blocking properties that may enhance the action of muscle relaxants used in anaesthesia, so tell the surgical or anaesthetic team if you are taking it.

Severe allergic and skin reactions have been reported, including Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS and Kounis syndrome. The leaflets say to stop and seek help for blistering, peeling skin, widespread rash with fever, swelling of the face or lips, or breathing difficulty. If you ever have a serious allergic reaction, call 999 or go to A&E, as the NHS advises.

The leaflets also ask you to tell the team if you have kidney or liver problems, because acute kidney problems have been reported and periodic liver and kidney tests are advised for prolonged treatment. If you notice passing much less urine, swollen ankles or breathlessness, contact a doctor.

The product information says capsules should be taken whole with a full glass of water and no less than 30 minutes before lying down, to avoid irritation of the gullet, and that food does not appreciably change absorption. For streptococcal infections it says treatment should continue for at least 10 days.

Long courses may lead to superinfection with organisms that do not respond to clindamycin, so repeated or prolonged use should be questioned. Breastfeeding mothers should tell the doctor, as the leaflet says clindamycin may pass into breast milk and a baby who develops bloodstained diarrhoea needs to be seen.

Clindamycin is prescribed in NHS hospitals, dental practices and general practice, and in private settings, under the same safety rules. If you receive it from a dentist, for example, make sure your GP records are updated so any bowel reaction can be linked to the antibiotic.