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Drugs that cause Constipation

🤓Let’s get down to the hard facts: some medications (notoriously opioids and anticholinergics) are associated with constipation.

💊They reduce activity in the nervous system and slow down the transit of food through the digestive system. The intestine walls absorb more fluid resulting in hard stools and constipation.

💧Drinking more fluids, eating more high fiber foods, and getting regular exercise may help relieve constipation. Using over the counter stool softeners and laxatives may also help.



Top Antibiotic Coverage Mnemonics

It is common for learners to struggle with memorizing antibiotic coverage when they are first introduced to the subject. With so many unfamiliar bacteria and antibiotics to know, it can be more than enough to get your head spinning.

In school, you probably learned the spectrum of activity for antibiotics by grouping bacteria into 3 common classifications:

Gram-positive bacteria (e.g., Streptococcus, Staphylococcus, Enterococcus)
Gram-negative bacteria (e.g., E. coli, Klebsiella, Salmonella, Shigella, Pseudomonas)
Atypicals (e.g., Chlamydophilia, Legionella, Mycoplasma)

Additionally, you learned that they are then further subclassified into aerobes, anaerobes, lactose-fermenting, and non-lactose-fermenting. But wait, don’t get cross-eyed just yet! Memorizing the spectrum of activity of antibiotics does not have to be that difficult. In this article, I’ll share some memorization tips on remembering the common bugs and what drugs cover them.


A great tip for remembering antibiotic coverage starts with memorizing the antibiotics that cover the major categories of bacteria including anaerobes and atypicals as well as resistant pathogens such as methicillin-resistant staphylococcus aureus (MRSA) and pseudomonas. From there, you can build upon your knowledge of other less commonly seen bacteria or infections through the application of the material during class, rotations, and clinical practice. 

Needless to say, these are a MUST for you to know for exams. Review the mnemonics below and quiz yourself to see how much you remember. 

NOTE: Clindamycin, doxycycline, and Bactrim (generic: sulfamethoxazole/trimethoprim) cover community-acquired MRSA infections while vancomycin, ceftaroline, and daptomycin cover hospital-acquired MRSA infections. Other antibiotics not listed include: linezolid, telavancin, dalbavancin, oritavancin, tigecycline (this mnemonic story can get pretty long!)

NOTE: Atypical bacteria do not color with Gram staining (because they lack a cell wall) and remain colorless. They are neither gram-positive nor gram-negative; they are ATYPICAL! 🙂

NOTE: These are the main antibiotics that empirically cover anaerobes. There are other antibiotics that do have some anaerobic coverage but since anaerobes are hard to culture and identify, empiric therapy is often used in practice.

NOTE: Other antibiotics not listed include: cefiderocol, colistin, ceftolozane/tazobactam


  • Keep in mind, memorizing these antibiotic spectra of activity can come in handy for exams but it doesn’t always apply to clinical practice (ex: you wouldn’t recommend daptomycin for MRSA pneumonia since daptomycin gets deactivated by the lung surfactants. You also wouldn’t recommend doxycycline as the first-line option for hospital-associated pneumonia.)
  • Other things to keep in mind when recommending an antibiotic to the team: potential toxicities, renal and hepatic function, CPK monitoring (esp. with daptomycin), which type of infection the drugs can or cannot be used for (moxifloxacin should not be used for UTIs as it doesn’t concentrate well in the urine making it ineffective), contraindications, drug interactions, and routine antibiotic doses (pneumonia dosing vs. bacteremia dosing)
  • At the end of the day, the best way to become comfortable with bugs and drugs is to practice, practice, practice. It takes time and effort but eventually, you’ll start to see a pattern with which antibiotic should be used based on patient-specific factors, cultures and sensitivity, and the type of infectious disease. 


A) Which of the following antibiotics can be used for a patient with MRSA+ pneumonia?

  1. Daptomycin
  2. Vancomycin
  3. Gentamicin
  4. Azithromycin

B) All of the following antibiotics cover pseudomonas EXCEPT for?

  1. Meropenem
  2. Cefepime
  3. Ertapenem
  4. Piperacillin/tazobactam

C) A patient is in need of anaerobic coverage for a diabetic foot infection, which of the following antibiotics would provide adequate anaerobe coverage?

  1. Levofloxacin
  2. Cefepime
  3. Clindamycin
  4. Tobramycin

D) Which antibiotic would provide coverage for atypical pathogens and streptococcus pneumoniae in a healthy patient diagnosed with community-acquired pneumonia (assuming local resistance is low)?

  1. Metronidazole
  2. Clindamycin
  3. Azithromycin
  4. Amoxicillin

ANSWERS: A. 2, B. 3., C. 3., D. 3. 

Hope these were helpful! If you have any additional memorization tips of your own, feel free to share them in the comments below. 

If you are interested in learning more, check out our Antibiotics Pharmacology Coloring Book or Top 200 Drugs Made Easy Coloring Book for additional memorization tips!

Uterine Relaxant Drugs

👶🏻 Preterm labor occurs when labor begins too early. If this happens before the 37th week of gestation, the fetal organs, especially the lungs, might not be fully developed.⁠

💊 In these cases, labor can be suppressed with uterine relaxants that relax the uterine muscle and slow down contractions for up to 48 hours. It gives the fetus a few more days in the uterus as a corticosteroid is given to speed up the development of a preterm infant’s lungs. Steroids help the lungs mature and may promote the production of surfactant, a substance that prevents the collapse of alveoli (small sacs in the lungs where the air is exchanged). ⁠

💊 Uterine relaxants are also called tocolytics (toco = childbirth, lytic = terminate) and include several different types of drugs. ⁠

Antibiotic Renal Dosing

Antibiotics are commonly used to treat infections. When considering what dose to prescribe to a patient, it is important to evaluate the patient’s renal function as many antibiotics are excreted by the kidney.⁠ ⁠ It is recommended to study the list of antibiotics that do NOT require renal dose adjustments rather than a list of the ones that do (as it can get very long and overwhelming). ⁠

Diuretic Classes

There are 5 main types of diuretic classes with different mechanisms of action, site of action, and side effect profiles. ⁠ ⁠ 1) Loop diuretics work on the loop of Henle (as the name implies)⁠ 2) Osmotic diuretic work on the glomerulus⁠ 3) Thiazides work on distal convoluted tubule⁠ 4) Carbonic anhydrase work on the proximal tubule⁠ 5) Potassium-sparing diuretics (aldosterone antagonists and sodium channel blockers) work on the distal convoluted tubule⁠ and collecting ducts
ketamine mnemonic

Ketamine Properties

📖 Ketamine is a medication primarily used for starting and maintaining anesthesia. It induces dissociative anesthesia, a trance-like state providing pain relief, sedation, and amnesia.⁠

⭐ The distinguishing features of ketamine anesthesia are preserved breathing and airway reflexes, stimulated heart function with increased blood pressure, and moderate bronchodilator.⁠

Antibiotics that Cover MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is an infection caused by Staphylococcus (staph) bacteria that has an oxacillin minimum inhibitory concentration (MIC) of greater than or equal to 4 micrograms/mL. ⁠ ⁠ ⭐ MRSA infection is one of the leading causes of hospital-acquired infections and is commonly associated with significant morbidity, mortality, length of stay, and cost burden. ⁠ ⁠ ⭐ MRSA infections can be further divided into hospital-associated (HA-MRSA) infections and community-associated (CA-MRSA) infections. They differ not only in respect to their clinical features and molecular biology but also to their antibiotic susceptibility and treatment⁠

Antibiotics that cover anaerobes

Anaerobic bacteria are bacteria that do not live or grow when oxygen is present. In humans, these bacteria are most commonly found in the gastrointestinal tract. ⁠ ⁠ 🔺 They play a role in conditions such as appendicitis, diverticulitis, and perforation of the bowel so it is important to make sure we have adequate anaerobic coverage when empirically treating these infections. ⁠ ⁠ 💊 There are several antibiotics that cover anaerobes in addition to other bacteria. ⁠

Antibiotics that cover Pseudomonas

Pseudomonas is a type of bacteria (bug) that is found commonly in soil and in water. Of the many different types of Pseudomonas, the one that most often causes infections in humans is called Pseudomonas aeruginosa, which can cause infections in the blood, lungs (pneumonia), or other parts of the body after surgery.⁠ ⁠ 🔺 Pseudomonas aeruginosa treatment has become increasingly difficult as bacteria become more resistant to the available antibiotics on the market. If they develop resistance to several types of antibiotics, these germs can become multidrug-resistant.⁠

Antituberculosis Agents

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (aerobic, non-spore forming bacillus). Active TB is transmitted by aerosolized droplets (sneezing, coughing, talking, etc.) and is highly contagious. ⁠ ⁠ Active disease treatment is divided into two treatment phases, initial and continuation. To avoid treatment failure due to resistance, the preferred initial treatment consists of a 4 drug regimen of rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE). ⁠ ⁠ These 4 drugs are taken for about 8 weeks during the initiation phase. In the continuation phase, the regimen is narrowed based on susceptibilities.

Beta-1 Cardioselective Beta-Blockers

❤️ Cardioselective beta-blockers work on the beta-1 receptors. Beta-1 receptors primarily are found in cardiac tissues whereas beta-2 receptors are located in the lungs (remember: 1 heart, two lungs). ⁠

❤️ Cardioselective beta-blockers exert their effect by binding to the beta-1 receptor sites selectively and inhibiting the action of epinephrine and norepinephrine on these sites. They are often preferred in patients with respiratory disease as they are less likely to cause constriction of airways or peripheral vasculature.⁠

Cholinergic Muscarinic Agonist Effects

👉🏻 Cholinergic muscarinic agonists are drugs that bind to and activate muscarinic cholinergic receptors and increase the activity of the parasympathetic nervous system. They are most commonly used when it is desirable to increase smooth muscle tone, especially in the GI tract, urinary bladder, and eye. They may also be used to reduce heart rate. ⁠

👉🏻 Direct cholinergic agonists work by resisting acetylcholinesterase, thus preventing its breakdown. Drugs in this class include bethanechol, carbachol, and methacholine, and pilocarpine.⁠

👉🏻 Indirect cholinergic agonists work by inhibiting the acetylcholinesterase enzyme preventing the degradation of acetylcholine. Drugs in this class include neostigmine, physostigmine, galantamine, donepezil, and rivastigmine. ⁠