Introduction

“Acid in the throat” also known as laryngopharyngeal reflux (LPR) or “silent reflux” occurs where stomach acid that causes symptoms like heartburn travels up to the throat. Both males and females can equally get LPR, with the average age experiencing this condition in their forties. The most frequent symptoms in those affected with LPR include feeling as though there is a lump in your throat and a hoarse voice. Patients with LPR are also shown to have thick mucus in their throat and swollen vocal cords. There are various types of medications that are available to treat LPR such as over-the-counter antacids, H₂ receptor antagonists and proton pump inhibitors (PPIs).¹ This report focuses on these three treatment options to establish its effectiveness in treating LPR.

Laryngopharyngeal reflux

LPR occurs when any one of the four areas are impaired: 

• The lower oesophageal sphincter: The muscle from the bottom of the oesophagus (food pipe) which meets the stomach and prevents food contents from travelling up to the throat
  
• The upper oesophageal sphincter: The muscle at the top of the oesophagus that stops food contents from entering the lungs and air entering the oesophagus when breathing
• Oesophageal peristalsis: The movement of food contents by muscle contractions, to allow it to travel from the oesophagus to the stomach
• Epithelial resistance factors: The muscle which is comprised of a mucus and aqueous layer combines with saliva to provide a natural protection against acid damage²

Causes

A great degree of patients with LPR have gastroesophageal reflux disease (GORD/GERD). However, currently there are no diagnostic tools to verify that LPR is due to GORD since some patients can have LPR even with no diagnosis of GORD. In GORD, stomach acid enters the oesophagus due to a damaged or weakened lower oesophageal sphincter.³ This causes symptoms such as heartburn, where patients experience a burning sensation in the chest,⁴ compared to LPR where symptoms are at the throat and affects the voice box.

Diet may also play a role in developing LPR. Foods high in fat, high in sugar and low protein can increase the risk of developing LPR. In comparison, a plant-based, alkaline diet that is low in fat, low in sugar and high in protein such as the Mediterranean diet have helped patients with LPR.⁵ 

Risk factors

LPR has also been associated with other conditions such as:⁶

• Sinusitis
• Polyps on the vocal cords
• Asthma

Additional symptoms

• Throat clearing
• Difficulty in swallowing
• Long-term coughing
• Mucus or postnasal drip
• Heartburn and indigestion

Treatment options

Antacids

Antacids are produced in different formulations such as tablets, suspensions and sachets. The most popular brands of antacids that are sold in the UK include Gaviscon® and Rennie®. The majority of antacids include the following ingredients for treating the symptoms: aluminium hydroxide, magnesium carbonate, magnesium trisilicate, magnesium hydroxide, calcium carbonate and sodium bicarbonate.⁷

Mechanism of action

Antacids neutralise acid to relieve the symptoms of heartburn and indigestion.

Calcium carbonate has a reaction with the hydrochloric acid in the stomach to form calcium chloride, carbon dioxide and water. The calcium ions promote the rhythmic muscle contractions along the digestive tract by moving the acid to the stomach to reduce heartburn symptoms. The carbonate ions bind to the hydrogen ions, which lowers the amount of hydrogen ions in the stomach, which in turn neutralises the stomach acid by raising the pH and making it more alkaline.

The other antacids work similarly in neutralising the pH of the acid. Sodium bicarbonate turns into sodium chloride, carbon dioxide and water, magnesium hydroxide turns into magnesium chloride, carbon dioxide and water and aluminium hydroxide turns into aluminium chloride, carbon dioxide and water when in contact with hydrochloric acid in the stomach.

Antacids have also shown to play a role in preventing pepsin and bile acid from damaging the oesophageal mucosal barrier (acting as a shield to protect the oesophagus from acidic food contents from the stomach).⁸

Some antacid products also combine with alginate to provide extra protection from the stomach acid such as Gaviscon®. Alginates are naturally occurring and are derived from brown seaweed, when it reacts with stomach acid a thick gel is created. Antacids like sodium bicarbonate then release carbon dioxide which gets trapped in the alginate gel and causes the gel to float upwards at the top of the stomach contents and form a raft. This prevents stomach contents from leaking into the oesophagus.⁹

Side effects

Generally, antacids can be very tolerable for patients, however some may have unwanted effects such as:⁷

• Stomach cramps
• Nausea and vomiting
• Diarrhoea or constipation
• Flatulence

H₂ Receptor Antagonists

H₂ receptor antagonists (histamine-2 receptor antagonists) such as famotidine, nizatidine and cimetidine are also used for treating LPR, they can come in either tablet form or as an oral solution. Of the H₂ receptor antagonists available, cimetidine is not usually prescribed due to the drug interacting with many medications. On average, H₂ receptor antagonists can take up to an hour for symptom relief, with the duration of action varying from four to ten hours.¹⁰

Mechanism of action

H₂ receptor antagonists lower LPR symptoms by binding to histamine H₂ receptors that are found on the stomach parietal cells (these play a role in producing stomach acid and help you absorb vitamin B₁₂). After having a meal, the hormone gastrin is released which stimulates histamine, histamine then binds onto the H₂ receptors located on the parietal cells in the stomach which produces stomach acid.¹⁰

Side effects

H₂ receptor antagonists are usually tolerated well with patients, however some may experience adverse effects such as:¹⁰

• Fatigue
• Drowsiness
• Constipation or diarrhoea
• Stomach pains
• Skin reactions
• Headaches

Proton Pump Inhibitors

Proton pump inhibitors (PPIs) such as omeprazole, esomeprazole, lansoprazole, pantoprazole and rabeprazole are also treatment options for LPR, they can come in tablet and capsule forms, oral suspension and solutions and as a powder for infusions. From the types of PPIs that are available, omeprazole, lansoprazole and esomeprazole are commonly prescribed in the UK. Compared to H₂ receptor antagonists, PPIs can take a few days to show benefit, and its duration of action is also slower.¹¹

Mechanism of action

PPIs lessens how much stomach acid is being released by binding onto the proton pump (also known as the hydrogen-potassium ATPase or H⁺/K⁺ ATPase enzyme) located on the parietal cells in the stomach. After a meal, gastrin is produced which triggers histamine release. When histamine is released, it attaches onto the H₂ receptors on the parietal cells to activate the proton pump and release stomach acid.¹²

Side effects

PPIs have similar adverse effects to H₂ receptor antagonists especially with short-term use such as:¹¹

• Constipation or diarrhoea
• Stomach pains
• Headaches
• Skin reactions
• Dizziness
• Nausea and vomiting

However, due to how common PPIs are usually prescribed in the UK, more serious adverse effects have been established especially with chronic use. Taking PPIs for long periods of time has demonstrated that it can lower magnesium levels in the blood. This is a rare adverse effect, where magnesium supplements do not usually help and patients would need to withhold treatment for levels to return back to normal. Long-term use has also been linked to an increased risk in infections, especially for clostridium difficile infections. Stomach acid protects the stomach from bacteria and other pathogens, therefore with PPIs reducing the levels of acid, this means that the body is more susceptible to infections. PPIs have also shown to reduce vitamin B₁₂ levels. Although a rare adverse effect, vitamin B₁₂ requires an acidic environment that stomach acid provides in order for it to be absorbed. PPIs can also cause rebound acid production especially discontinuing the drug after chronic use. Other adverse effects due to long-term use include increased fracture risk, increased risk in stomach cancers, pneumonia and liver disease.^11,12

Antacids vs. H₂ Receptor Antagonists vs. Proton Pump Inhibitors in Laryngopharyngeal Reflux

Since the pathophysiology of laryngopharyngeal reflux is still uncertain, there is no definitive treatment to treat the condition. The three treatment options described are trialled in patients, with PPIs being first line especially in those with GORD symptoms too. PPIs are usually recommended over H₂ receptor antagonists (which are second line) because they are stronger in suppressing stomach acid and have a longer duration of action. Some patients do not respond to PPIs and a combination of a PPI and an antacid can help.^6,14

Summary

Laryngopharyngeal reflux can be a debilitating condition where the throat and vocal cords are affected due to stomach acid damage. Because the origin of the condition is still inconclusive, there is no clear treatment plan, with medications such as antacids, H₂ receptor antagonists and proton pump inhibitors being trialled in patients. Therefore, more research is required to determine a treatment plan in patients that have residual symptoms despite trying all three options. It is recommended to speak to your healthcare provider to discuss other options that are available if you have laryngopharyngeal reflux and have ongoing symptoms.