This study seeks to address the question of whether antacids or multivitamins influence the pharmacokinetics of raltegravir when co-administered. The aim of this study is to optimise the dosing of raltegravir when co-administered with antacids or multivitamins.

Inclusion Criteria:

• The ability to understand and sign a written informed consent form, prior to participation in any screening procedures and must be willing to comply with all study requirements.
• ≥ 18 years
• Male or female subjects
• A female may be eligible to enter and participate in the study if she:
• Is of non-child-bearing potential defined as ether post-menopausal (12 months of spontaneous amenorrhea and ≥ 45 years of age)or physically incapable of becoming pregnant with documented tubal ligation, hysterectomy or bilateral oophorectomy or
• Is of child-bearing potential with a negative pregnancy test at screening and agrees to use one of the following methods of contraception to avoid pregnancy
• Complete abstinence from intercourse from 2 weeks prior to administration of IP, throughout the study and for at least 4 weeks after discontinuation of all study medication
• Double barrier method (male condom/spermicide, male condom/diaphragm, diaphragm/spermicide)
• Any intrauterine device (IUD) with published data showing that the expected failure rate is < 1 % per year
• Any other method with published data showing that the expected failure rate is < 1 % per year
• Hormonal contraception plus a barrier method. Hormonal contraception alone will not be considered adequate for inclusion into or participation in this study
• Male subjects with a female partner of childbearing potential must agree to use effective contraception as above unless vasectomized
• All subjects participating in the study will be counseled on safer sexual practices including the use of effective barrier methods (e.g. male condom)

Exclusion Criteria:

• Any significant acute or chronic medical condition
• Pregnant or lactating women
• Women of childbearing age unless using non hormonal contraception
• Evidence of organ dysfunction or any clinically significant deviation from normal during screening including laboratory determinations
• Abnormal LFTs (ALT > 2.5 x ULN, bilirubin > 1.5 x ULN)
• Positive blood screen for HIV-1 and 2 antibodies
• Positive blood screen for hepatitis B or C antibodies
• Current or recent (within 3 months) gastrointestinal disease
• Clinically relevant alcohol or drug use or history of alcohol or drug use that will hinder compliance with treatment, follow up procedures or evaluation of adverse effects
• Use of proton pump inhibitors
• Exposure to any investigational drug or placebo within 4 weeks of first dose of study drug
• Consumption of grapefruit and oranges or products containing grapefruit or oranges within 1 week of first study drug and for the duration of the study
• Use of any other drugs including over-the-counter medications and herbal preparations, within 2 weeks prior to first dose of study drug
• Previous allergy to any of the constituents of the pharmaceuticals in this trial