Chapter 24: Dermatologic Medications

SYSTEMIC MEDICATIONS

Androgenetic Alopecia Treatment

FINASTERIDE

• Mechanism of action: inhibits type II 5α-reductase, which converts testosterone to dihydrotestosterone (DHT)

• Adverse effects: decreased libido, erectile dysfunction, decreased volume of ejaculate, teratogenicity (causes GU defects in male offspring)

• Pregnancy category X

MINOXIDIL

• Mechanism of action

  • Increases duration of anagen growth phase, gradually enlarges miniaturized hairs

  • Opens ATP-sensitive potassium channels; release of adenosine stimulates VEGF, a proposed promoter of hair growth

  • Stimulates prostaglandin production

• Adverse effects: irritant and allergic contact dermatitis (topical), hypertrichosis; may exacerbate angina pectoris (oral); caution in pulmonary hypertension, congestive heart failure, coronary artery disease, and significant renal failure (oral)

• Pregnancy category C

SPIRONOLACTONE

• Mechanism of action: aldosterone antagonist, weak antiandrogen activity by blocking androgen receptor and inhibiting androgen biosynthesis; may be converted by progesterone 17-hydroxylase to active metabolites that decrease testosterone and DHT production

• Clinical use: dermatologic uses are off label and include acne vulgaris, androgenetic alopecia, hirsutism, hidradenitis suppurativa

• Adverse effects: menstrual irregularities, hyperkalemia, hyponatremia, potential teratogenicity as an antiandrogen (feminization of male fetus), gynecomastia

• Contraindications: renal insufficiency, hyperkalemia, pregnancy, abnormal uterine bleeding, family or personal history of estrogen-dependent malignancy

• Drug interactions: increased potential of hyperkalemia with angiotensin-converting enzyme inhibitors, thiazide diuretics, potassium supplements

• Increased levels of digoxin if taken with spironolactone

• Pregnancy category X

Antibiotics

AMINOGLYCOSIDES

• Gentamicin, tobramycin, and amikacin

• Mechanism of action

  • Bind to 30S subunit of bacterial ribosomes to inhibit protein synthesis

• Active against aerobic gram-negative organisms

• Adverse effects: ototoxicity, nephrotoxicity, neuromuscular blockade, injection site necrosis

• Pregnancy category D

BETA-LACTAM ANTIBIOTICS

• Include penicillins and cephalosporins

• Active against many gram-positive, gram-negative, and anaerobic organisms

CEPHALOSPORINS

• Mechanism of action: inhibit bacterial cell wall synthesis through inhibition of penicillin-binding proteins

• Treat soft tissue infections caused by Streptococci, methicillin-sensitive Staphylococcus aureus, some gram-negative bacilli

• Adverse effects: hypersensitivity, gastrointestinal (GI) upset, dizziness, Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), Clostridium difficile colitis, serum sickness–like reaction (Cefaclor), acute generalized exanthematous pustulosis (AGEP), thrombocytopenia, neutropenia, eosinophilia; cross-reactivity with penicillins: 5 to 20%

• Drug interactions

  • Probenecid: increases levels of B-lactam medications

  • Allopurinol: increases hypersensitivity reaction of ampicillin

• Pregnancy category B

PENICILLINS

• Mechanism of action

  • Inhibit bacterial cell wall synthesis; lead to activation of autolytic enzymes that kill the bacteria

  • Active against gram-positive organisms and spirochetes

• Penicillinase-resistant penicillins include dicloxacillin, nafcillin, and oxacillin

• Beta-lactamase inhibitors: ampicillin-sulbactam, amoxicillin-clavulanic acid; used in the treatment of bite wounds; active against oral anaerobes, streptococci, anaerobes, and staphylococci

• Adverse effects: hypersensitivity reactions (mild morbilliform to anaphylaxis), hemolytic anemia, nephritis, TEN, erythema nodosum, cutis laxa, AGEP

• Ampicillin causes a morbilliform eruption when given to patients ...