What is Clindamycin Phosphate?

Published August 2nd, 2021 by Nicole Salata, PharmD, MSHI
Fact Checked by
Chris Riley
Medically Reviewed:
Dr. Angel Rivera

Clindamycin phosphate is a salt form of the antibiotic medicine clindamycin. Clindamycin phosphate provides coverage for bacteria that are resistant to erythromycin, methicillin, or penicillin. Clindamycin is used to treat acne, also known as acne vulgaris, as well as other bacterial infections. Let's take a closer look at what it is and how it can help you.

What is Clindamycin?

Clindamycin is an antibiotic that was developed in the 1960s. It belongs to the antibiotic class “lincosamide”; this means that all antibiotics in the lincosamide class most closely resemble lincomycin in both structure and function. The lincosamide class of antibiotics is unlike any other class of antibiotics; this is especially important because it is useful for people who may have allergies to one or more other types of antibiotics.

How does Clindamycin Work?

As an antibiotic, clindamycin is effective against many different types of bacteria. However, it is most well-known for its activity against anaerobic bacteria, or those that can thrive in environments without oxygen that is not exposed to the air. 

Additionally, clindamycin is unique in how it works as an antibiotic. Most antibiotics are either bactericidal or bacteriostatic. Bactericidal means that it actually kills bacteria. Bacteriostatic means that it prevents bacteria from replicating. While this doesn’t kill the infection immediately, bacterial colonies that cannot replicate cannot grow; this means that as each cell dies, there are no new cells to replace it, and the infection eventually dies and is stopped. Clindamycin, however, can do both of these. At lower concentrations it is bacteriostatic, and at higher concentrations it is bactericidal. So patients have the unique opportunity to use this drug for both. 

Another unique feature of clindamycin is that it has shown anti-inflammatory effects in some types of infections. Since inflammation and swelling are two symptoms of the infection process that can be particularly uncomfortable, this can help ease some of the discomforts of some infections until the infection is cured. 

Finally, clindamycin is one of several antibiotics that has a post-antibiotic effect. This is exactly what it sounds like: even after the antibiotic is stopped, it keeps working for a period of time. This is helpful because it can help your doctor or dermatologist shorten the amount of time on the antibiotic or allow fewer doses to be used without making it less effective at curing the infection. As always, please follow the advice on your prescription and the instructions of your medical professional. 

Why does Clindamycin Come in Salt Forms?

Like any medication, clindamycin must be stabilized so that it can sit on the store shelf for a while before being needed or used and the most stable form is in salt form. Additionally, the medicine needs to be stabilized so that once in or on the body, it is ready when it needs to be used. A final reason is that, in some cases, salt forms affect how medications taste. A specific salt form may exist simply to make the medication taste better and be easier to take. 

What are the Salt Forms of Clindamycin?

Clindamycin comes in three salt forms: clindamycin hydrochloride (HCl), clindamycin palmitate HCl, and clindamycin phosphate. 

Clindamycin HCl and Clindamycin Palmitate HCl

Clindamycin HCl and clindamycin palmitate HCl are both oral formulations meant to be taken by mouth and swallowed. Clindamycin HCl is typically in powdered form and contained in capsules, anywhere from 75mg to 300mg. Clindamycin palmitate HCl is the salt form used for an oral suspension. Available in granulated form, it must be reconstituted, or dissolved in water, to a final concentration of 75mg per 5ml, or teaspoonful. This formulation is mostly used for children and adults that cannot swallow capsules. While this salt form tastes better than clindamycin HCl, many still consider it to have a foul taste and smell. 

Clindamycin phosphate

Clindamycin phosphate is the final salt form, and it is used in both topical and injectable formulations. For injectable medications, it is available for direct injection in the muscle (IM), or it is available in a reconstitutable formulation that must be diluted for intravenous (IV) use. The topical forms of clindamycin include a gel, solution, and lotion for regular skin application, but not mucous membranes, as well as a cream and ovule for vaginal use.  All of these topical and injectable formulations are water-based—they contain water in contact with the medicine. Since these dosage forms sit on the shelf in a water-based formulation, unlike the capsules or granules for suspension, they need the most stability. The stability is greatest in these conditions in the phosphate salt form. 

What is Clindamycin Phosphate Used For?

As previously mentioned, clindamycin phosphate is used for topical and injectable dosage forms. The gel, solution, foam, and lotion topical forms are most commonly used to treat acne. The vaginal cream and ovule are used to treat certain vaginal and pelvic bacterial infections. The intravenous dosage forms are mostly used to prevent infections from surgery or to treat infections in the lower respiratory tract or abdomen. They may also be used for other conditions. Clindamycin phosphate is only available with a prescription from a doctor or medical provider in the United States. Your doctor may also recommend that you take other medicines in combination with clindamycin for treatment, the most popular being topical solutions like benzoyl peroxide and salicylic acid when using clindamycin for the treatment of acne.  For more information on the use of clindamycin, see the article What is Clindamycin Used For [insert hyperlink] or consult with your health care provider. 

What are the Side Effects of Clindamycin?

Although adverse reactions do occur with this product, they are very rare. Just in case, we will cover the most common adverse effects that happen with the use of this medicine as serious side effects can occur. 

Clindamycin phosphate is a salt form taken orally that may have side effects. The most common among these are nausea and vomiting, abdominal pain or cramps, diarrhea, bloody diarrhea, rash, and even the possibility of a metallic taste in your mouth. Pseudomembranous colitis is also a common side effect.  

On the other hand, topical forms of clindamycin carry their own risks for side effects as well. These include dryness, burning, itching, and peeling of the skin over the affected area that was treated with a clindamycin phosphate topical solution. Patients may also experience erythema, a type of rash, and oiliness of the skin. Again, severe skin reactions are rare but they do happen and you may need to seek other forms of medical treatment. 

It should also be noted here that the use of clindamycin by pregnant women during pregnancy is generally considered safe. However, the American Academy of Pediatrics states that the drug is compatible with breastfeeding while the World Health Organization, or WHO, recommends avoiding breastfeeding while on this medication if possible.

Should you experience an allergic reaction or any of the symptoms pleases seek medical help for advice on how to proceed with your treatment. 


Clindamycin phosphate is a salt form of clindamycin that is most commonly used for skin conditions while the other two salt formulations of clindamycin are meant to be taken orally. In its topical form, clindamycin is mainly used to treat acne on the face, neck, back, or chest area. Clindamycin phosphate is more stable and has a broader use in both topical forms, injectable formulations, pills, and oral solutions. The most common topical form of clindamycin phosphate for acne treatment is in a gel, lotion, cream, foam, or serum form and it can also be found in a cream or ovule form for vaginal conditions. For intravenous dosage forms of clindamycin phosphate, it may be used to prevent infections from surgery or to treat infections in the lower respiratory tract or abdomen. Should you experience any adverse reactions, we urge you to seek medical advice immediately. Please talk to your doctor or pharmacist to see if it is right for you.

References and Sources:

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CUNLIFFE WJ, C'OTTERILL JA, WILLIAMSON B. THE EFFECT OF CLINDAMYCIN IN     ACNE-A CLINICAL AND LABORATORY INVESTIGATION. British Journal of     Dermatology. 1972;87(1):37-41. doi:https://doi.org/10.1111/j.1365-2133.1972.tb05095.x

Dawson AL, Dellavalle RP. Acne vulgaris. BMJ : British Medical Journal. 2013;346:f2634.     doi:10.1136/bmj.f2634

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Frankel RI. Clindamycin--efficacy and toxicity. The Western journal of medicine.     1975;122(6):526-530.

Smieja M. Current Indications for the Use of Clindamycin: A Critical Review. Canadian Journal     of Infectious Diseases. 1900/01/01 1998;9:538090. doi:10.1155/1998/538090

Spížek J, Řezanka T. Lincomycin, clindamycin and their applications. Applied Microbiology and     Biotechnology. 2004/05/01 2004;64(4):455-464. doi:10.1007/s00253-003-1545-7

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