Trimethoprim (TMP) is an antibiotic that is used to treat certain types of urinary tract, ear and intestinal infections that are caused by bacteria. It is is commonly included in combination antibiotics with Sulfamtheoxazole, Dapsone and other Sulfonamide antibiotics.
Trimethoprim inhibits the ability of bacteria to synthesize vitamin B9 (Folate) by a mechanism that complements the antibacterial activity of Sulfonamide antibiotics.
Trimethoprim is occasionally used alone as a treatment for acne. There is limited clinical research into the efficacy of Trimethoprim alone as an acne treatment, but some acne patients have reported positive results with this medication.
Laboratory testing indicates that the acne-causing P. acnes bacterium tends to be moderately susceptible to Trimethoprim, but Trimethoprim-resistant P. acnes are becoming more common in some places.
The combination of Trimethoprim plus Sulfamethoxazole (CoTrimoxazole) is a more common and effective acne treatment. Oral Cotrimoxazole can be a very effective treatment for some individuals with moderate to severe inflammatory acne symptoms. CoTrimoxazole is a popular choice for acne patients who have not responded to other types of antibiotics (eg. Doxycycline, Minocycline, Erythromycin).
Nitrofurantoin (Macrodantin) is an antibiotic that is used to treat certain kinds of bacterial infections, primarily urinary tract infections. Nitrofurantoin is not a commonly used antibiotic, but the increasing incidence of antibiotic-resistant bacteria has generated renewed interest in this medication.
Nitrofurantoin is rarely used as a treatment for acne. There is very little clinical or laboratory research into the effectiveness of Nitrofurantoin as a treatment for active acne symptoms, or into the sensitivity of the acne-causing P. acnes bacterium to this antibiotic. However, laboratory testing does indicate that gram-positive bacteria, a group which includes P. acnes, tend to be susceptible to this Nitrofurantoin.
Additional clinical testing and patient surveys will be required to evaluate the utility of Nitrofurantoin as a component of acne treatment regimens.
Isoniazid (isonicotinylhydrazide) is an antibiotic that is part of the standard antibiotic regimen for treating tuberculosis infections. Isoniazid is an antibiotic that is only active against a certain type of bacteria (Mycobacteria). Isoniazid is not used as a treatment for acne. In fact, Isoniazid use has been reported to increase acne symptoms in some patients.
Gramicidin is a topical antibiotic that is used to treat certain skin infections that are caused by gram-positive bacteria. Gramicidin is commonly included with other antibiotics in combination antibacterial ointments for topical use. Gramicidin is a mixture of several closely related antibacterial molecules, Gramicidin A, Gramicidin B and Gramicidin C.
Gramicidin containing ointments are occasionally used as topical treatments for acne symptoms. The acne-causing P. acnes bacterium appears to have some natural resistance to this antibiotic. It is also unclear whether topically applied Gramicidin penetrates the skin and reaches the sebaceous glands in significant concentrations.
Topical Gramicidin ointments are more likely to be effective at preventing secondary infections after acne lesions have been “popped” or drained, and these antibiotics may accelerate healing time and help prevent some scarring.
Colistin (Polymyxin E) is an antibiotic in the Polypeptide family. It is available topical formulations. Colistin is rarely used as a treatment for acne.
Colistin is not usually active against Gram-positive bacteria. Because the acne-causing P. acnes bacterium is Gram-positive, Colistin is not expected to be a useful treatment for acne patients. Colistin is commonly used in veterinary medicine.
Bacitracin is an antibiotic that is a mixture of closely related antibacterial molecules. Bacitracin can inhibit the growth of many kinds of bacteria, including S. aureus and P. acnes.
Bacitracin is applied topcially for the treatment of acne. However, user and research reports suggest that Bacitracin is not an effective acne treatment, particularly for moderate to severe inflamatory acne. Triple antibiotic ointments (eg. Neosporin) usually include Bacitracin as an active ingredient.
Bacitracin is known to cause allergic skin reactions in some people.
Mupirocin is a topical antibiotic that is used to treat certain types of bacterial skin infections, including acne.
The use of Mupirocin for the treatment of acne is somewhat controversial. Many individuals have reported that using Mupirocin helped improve their acne symptoms. However, laboratory antibiotic susceptibility testing has shown that many strains of the acne-causing P. acnes bacterium are naturally resistant to Mupirocin. Because of this natural resistance, Mupriocin is frequently ineffective as an acne treatment.
Mupirocin is also used to treat a variety of skin infections that are caused by gram-positive bacteria, including methicillin resistant S. aureus (MRSA). The activity of Mupirocin against other types of bacteria than P. acnes, may explain some of the benefit that certain patients have reported.