- (Anti hemorrhoidals)
- (Contraceptive combined Estrogen & Progestins)
- (Corticosteroids)
- (Gadolinium-Based RMI Contrast Agents)
- (General Anesthesia)
- (Iodide Radiopaque Agent)
- 5-Aminolevulinic Acid
- Abacavir
- Abatacept
- Abciximab
- Acamprosate Calcium
- Acarbose
- Accidental Puncture by Contaminated Needles
- Acebutolol
- Aceclofenac
- Acenocoumarol
- Acetazolamide
- Acetohexamide
- Acetophenazine
- Acetylcholine Chloride
- Acetylcysteine
- Acitretin
- Acne
- Acrivastine
- Activated Charcoal
- Acupuncture
- Acute Gastroenteritis In The Infant
- Acyclovir
- Adalimumab
- Adapalene
- Adefovir Dipivoxil
- Ademetionine
- Adenosine
- Adenosine-Monophosphate
- Adenosine-Triphosphate
- Adrenaline
- Aescin
- Aesculin
- Aflatoxin
- Aflibercept, Ophthalmic use
- African Cherry
- Agomelatine
- Airborne
- Airplane, Flying
- Albendazole
- Albuterol
- Alcaftadine
- Alcuronium Chloride
- Alefacept
- Alemtuzumab