Names: Raltegravir, Isentress 

Dose: One pink 400mg tablet twice daily. 

Tips on taking it: Take with or without food. 

Important warning: An allergic (hypersensitivity) reaction has been reported in some people using raltegravir. See your HIV clinic immediately (or A&E if out of hours) if you develop a rash together with any of these symptoms: fever; feeling generally unwell or extremely tired; muscle or joint ache; blistering of the skin; mouth ulcers; swelling of the eye, lips, mouth or face; breathing difficulties; yellowing of the skin or eyes; dark urine; pale stools; or pain, aching or sensitivity on the right-hand side of the body, below the ribs.

Common side-effects: Headache, insomnia. 

Rare side-effects: Severe rash, hypersensitivity reaction, extreme thirst (polydipsia).

Key drug interactions: If you are prescribed the TB drug rifampicin, your dose of raltegravir may be increased to 800mg (two tablets) twice daily, as rifampicin can reduce drug levels of raltegravir.